Convenience base trait for string Uniformity
s.
Convenience base trait for string Uniformity
s.
This trait defines a normalizedCanHandle
method that returns true if the passed
Any
is a String
and a normalizedOrSame
method that
normalizes any passed String
s via the normalized
method, which is
left abstract for subclasses to fill in.
Here's an example in which AbstractStringUniformity
is used to normalize strings
by ensuring the first character, if any, is capitalized:
val capitalized: Uniformity[String] = new AbstractStringUniformity { def normalized(s: String): String = if (s.isEmpty) "" else s.charAt(0).toUpper + s.substring(1) }
Here's an example of using the capitalized
Uniformity
with a Matcher
expression:
scala> import org.scalatest._ import org.scalatest._ scala> import Matchers._ import Matchers._ scala> import org.scalactic._ import org.scalactic._ scala> val capitalized: Uniformity[String] = | new AbstractStringUniformity { | def normalized(s: String): String = | if (s.isEmpty) "" else s.charAt(0).toUpper + s.substring(1) | } capitalized: org.scalactic.Uniformity[String] = $anon$1@65601e00 scala> "Hello" should equal ("hello") (after being capitalized)
Provides mechanisms that enable errors to be accumulated in “accumulating Or
s,” Or
s whose
Bad
type is an Every
.
Provides mechanisms that enable errors to be accumulated in “accumulating Or
s,” Or
s whose
Bad
type is an Every
.
The mechanisms are:
Or
s to withGood
methodscombined
on a container of accumulating Or
svalidatedBy
on a container of any type, passing in a function from that type to an accumulating Or
zip
on an accumulating Or
when
on an accumulating Or
For more information and examples, see the Accumulating errors with Or
section
of the main documentation for class Or
.
A trait that represent a rich-featured boolean value, which includes the following members:
A trait that represent a rich-featured boolean value, which includes the following members:
Bool
composableBool
is used by code generated from BooleanMacro
(which AssertionsMacro
and RequirementsMacro
uses),
it needs to be public so that the generated code can be compiled. It is expected that ScalaTest users would ever need to use Bool
directly.
Abstract class used to enforce type constraints for equality checks.
Abstract class used to enforce type constraints for equality checks.
For more information on how this class is used, see the documentation of TripleEqualsSupport
.
Convenience class for extractors that match and return Throwable
s based on a type and Boolean
condition.
Convenience class for extractors that match and return Throwable
s based on a type and Boolean
condition.
Class Catcher
was motivated by the need to catch
and handle exceptions based on more than just the exception's type as a strategy for dealing with
"flickering" tests—tests that usually pass, but occasionally fail. The best strategy for dealing with
flickers is to fix the test such that they stop flickering, but sometimes that is not practical. In
such cases allowing the test to continue flickering can distract the team by requiring them to
spend time inspecting failures to determine whether or not they are flickers or real failures that need
attention. Worse, with enough flickers, team members can stop checking all failures and not notice real ones.
One strategy for dealing with flickers you can't practically fix is to catch exceptions that are causing individual flickers
and cancel the test when you detect them. Often this means you will need to insert a catch clause in a particular spot, or a pattern
match if in a withFixture
, looking for a particular exception with a particular message or other identifying attribute. If
the same problem is causing flickers in many places,
it is handy to create an extractor to detect the problem. This Catcher
class provides
a factory method that takes a partial function from Throwable
to Boolean
and produces such an extractor.
Here's an example:
val InternalServerError = Catcher { case e: DBAccessException => e.getMessage == "500:Internal Server Error" }
Using this Catcher
in a ScalaTest withFixture
method would look like:
override def withFixture(test: NoArgTest) = { super.withFixture(test) match { case Failed(InternalServerError(ex)) => Canceled("Canceled because likely a flicker caused by intermittently flaky DB", ex) case other => other } }
Defines a custom way to determine equality for a type when compared with another value of type Any
.
Defines a custom way to determine equality for a type when compared with another value of type Any
.
Equality
enables you to define alternate notions of equality for types that can be used
with ScalaUtil's ===
and !==
syntax and ScalaTest's matcher syntax.
For example, say you have a case class that includes a Double
value:
scala> case class Person(name: String, age: Double) defined class Person
Imagine you are calculating the age
values in such as way that occasionally tests
are failing because of rounding differences that you actually don't care about. For example, you
expect an age of 29.0, but you're sometimes seeing 29.0001:
scala> import org.scalactic._ import org.scalactic._ scala> import TripleEquals._ import TripleEquals._ scala> Person("Joe", 29.0001) === Person("Joe", 29.0) res0: Boolean = false
The ===
operator looks for an implicit Equality[L]
, where L
is the left-hand type: in this
case, Person
. Because you didn't specifically provide an implicit Equality[Person]
, ===
will fall back on
default equality, which will call Person
's equals
method. That equals
method, provided by the Scala compiler
because Person
is a case class, will declare these two objects unequal because 29.001 does not exactly equal 29.0.
To make the equality check more forgiving, you could define an implicit Equality[Person]
that compares
the age
Double
s with a tolerance, like this:
scala> import Tolerance._ import Tolerance._ scala> implicit val personEq = | new Equality[Person] { | def areEqual(a: Person, b: Any): Boolean = | b match { | case p: Person => a.name == p.name && a.age === p.age +- 0.0002 | case _ => false | } | } personEq: org.scalactic.Equality[Person] = $anon$1@2b29f6e7
Now the ===
operator will use your more forgiving Equality[Person]
for the equality check instead
of default equality:
scala> Person("Joe", 29.0001) === Person("Joe", 29.0) res1: Boolean = true
Scalactic defines a default Equality[T]
for all types T
whose areEqual
method works by first
calling .deep
on any passed array, then calling ==
on the left-hand object, passing in the right-hand object.
You can obtain a default equality via the default
method of the Equality companion object,
or from the defaultEquality
method defined in TripleEqualsSupport
.
The Equality
trait represents the Java Platform's native notion of equality, as expressed in the signature and contract of
the equals
method of java.lang.Object
. Essentially, trait Equality
enables you to write alternate
equals
method implementations for a type outside its defining class.
In an equals
method, the left-hand type is known to be the type of this
, but
the right-hand type is Any
.
As a result, you would normally perform a runtime type test to determine whether the right-hand object is of an appropriate type for equality,
and if so, compare it structurally for equality with the left-hand (this
) object.
An an illustration, here's a possible equals
implementation for the Person
case class shown in the earlier example:
override def equals(other: Any): Boolean = other match { case p: Person => name = p.name && age = p.age case _ => false }
The areEquals
method of Equality[T]
is similar. The left-hand type is known to be T
, but the right-hand type is Any
, so
normally you'd need to do a runtime type test in your areEqual
implementation.
Here's the areEqual
method implementation from the earlier Equality[Person]
example:
def areEqual(a: Person, b: Any): Boolean = b match { case p: Person => a.name == p.name && a.age === p.age +- 0.0002 case _ => false }
Equality
is used by TripleEquals
, which enforces no type constraint between the left and right values, and the
equal
, be
, and contain
syntax of ScalaTest Matchers.
By contrast, TypeCheckedTripleEquals
and ConversionCheckedTripleEquals
use an Equivalence
.
Equivalence
differs from Equality
in that both the left and right values are of the same type. Equivalence
works for
TypeCheckedTripleEquals
because the type constraint enforces that the left type is a subtype or supertype of (or the same type as) the right
type, and it widens the subtype to the supertype. So ultimately, both left and right sides are of the supertype type. Similarly, Equivalence
works for ConversionCheckedTripleEquals
because the type constraint enforces that an implicit conversion
exists from either the left type to the right type, or the right type to the left type, and it always converts one
type to the other using the implicit conversion. (If both types are the same type, the identity implicit conversion
from Predef
is used.) Because of the conversion, both left and right sides are ultimately of the
converted-to type. Here's an example of how writing an Equivalence
's areEquivalent
method might look:
def areEquivalent(a: Person, b: Person): Boolean = a.name == b.name && a.age === b.age +- 0.0002
Scalactic provides both Equality
and Equivalence
because the Any
in
Equality
can sometimes make things painful. For example, in trait
TolerantNumerics
,
a single generic factory method can produce Equivalence
s for any Numeric
type,
but because of the Any
, a separate factory method must be defined to produce an Equality
for each Numeric
type.
If you just want to customize the notion of equality for ===
used in Boolean
expressions, you can work with Equivalence
s instead of Equality
s.
If you do chose to write the more general Equality
s, they can be used wherever an Equivalence
is required, because Equality
extends Equivalence
, defining a final implementation of
areEquivalent
that invokes areEqual
.
Note: The Equality
type class was inspired in part by the Equal
type class of the
scalaz
project.
the type whose equality is being customized
Defines a custom way to determine equality for a type when compared with another value of the same type.
Defines a custom way to determine equality for a type when compared with another value of the same type.
Equivalence
enables you to define alternate notions of equality for types that can be used
with ScalaUtil's TypeCheckedTripleEquals
and
ConversionCheckedTripleEquals
traits. These traits can be used to perform equality comparisons with type constraints enforced at
compile time using ScalaUtil's ===
and !==
syntax
and ScalaTest's should
===
syntax of Matchers
trait.
Because Equality
extends Equivalence
, you automatically
define an Equivalence[T]
when you define an Equality[T]
. Most often you will usually
want to define custom Equality
s, because they will be more generally useful: they are also
used by Scalactic's TripleEquals
trait and ScalaTest's
equal
, be
, and contain
matcher syntax. However, if you really want
just an Equivalence
, and writing an Equality
is inconvenient, you can write
an Equivalence
directly for a type.
For example, say you have a case class that includes a Double
value:
scala> case class Person(name: String, age: Double) defined class Person
Imagine you are calculating the age
values in such as way that occasionally tests
are failing because of rounding differences that you actually don't care about. For example, you
expect an age of 29.0, but you're sometimes seeing 29.0001:
scala> import org.scalactic._ import org.scalactic._ scala> import TypeCheckedTripleEquals._ import TypeCheckedTripleEquals._ scala> Person("Joe", 29.0001) === Person("Joe", 29.0) res0: Boolean = false
The ===
operator of TypeCheckedTripleEquals
looks for an implicit
Equivalence[SUPER]
, where SUPER
is either the left-hand or right-hand type, whichever
one is a supertype of the other. In this case, both sides are Person
(which is considered a supertype of
itself), so the compiler will look for an Equivalence[Person]
.
Because you didn't specifically provide an implicit Equivalence[Person]
, ===
will fall back on
default equality, because an Equality[Person]
is-an
Equivalence[Person]
. The default Equality[Person]
will call Person
's
equals
method. That equals
method, provided by the Scala compiler
because Person
is a case class, will declare these two objects unequal because 29.001 does not
exactly equal 29.0.
To make the equality check more forgiving, you could define an implicit Equivalence[Person]
that compares
the age
Double
s with a tolerance, like this:
scala> import Tolerance._ import Tolerance._ scala> implicit val personEq = | new Equivalence[Person] { | def areEquivalent(a: Person, b: Person): Boolean = | a.name == b.name && a.age === b.age +- 0.0002 | } personEq: org.scalactic.Equivalence[Person] = $anon$1@7892bd8
Now the ===
operator will use your more forgiving Equivalence[Person]
for the
equality check instead of default equality:
scala> Person("Joe", 29.0001) === Person("Joe", 29.0) res1: Boolean = true
Type alias for String
.
Type alias for String
.
Provides ScalaTest's “explicitly DSL,” which facilitates the
explicit specification of an Equality[T]
or a Uniformity[T]
where
Equality[T]
is taken implicitly.
Provides ScalaTest's “explicitly DSL,” which facilitates the
explicit specification of an Equality[T]
or a Uniformity[T]
where
Equality[T]
is taken implicitly.
The Explicitly DSL can be used with the ===
and !==
operators of Scalactic
as well as the should
equal
, be
, contain
, and
===
syntax of ScalaTest matchers.
If you want to customize equality for a type in general, you would likely want to place an
implicit Equality[T]
for that type in scope (or in T
's companion object). That implicit
equality definition will then be picked
up and used when that type is compared for equality with the equal
, be
, and
contain
matchers in ScalaTest tests and with
===
in both tests and production code.
If you just want to use a custom equality for a single comparison, however, you may prefer to pass it explicitly. For
example, if you have an implicit
Equality[String]
in scope, you can force a comparison to use the default equality with this syntax:
// In production code: if ((result === "hello")(decided by defaultEquality)) true else false // In tests: result should equal ("hello") (decided by defaultEquality)
The explicitly DSL also provides support for specifying a one-off equality that is based on a normalization. For
example, Scalactic offers a StringNormalizations
trait that
provides methods such as trimmed
and lowerCased
that return
Normalization[String]
instances that normalize by trimming and lower-casing, respectively. If you bring
those into scope by mixing in or importing the members of StringNormalizations
, you could use the
explicitly DSL like this:
// In production code: if ((result === "hello")(after being lowerCased)) true else false // In tests: result should equal ("hello") (after being lowerCased and trimmed)
If you prefer not to use English-like DSLs in your production code, you can alternatively
not use the Explicitly
trait and instead write:
// To explicitly specify an Equality instance, just specify it: if ((result === "hello")(Equality.default)) true else false // To base an Equality instance on a Uniformity, just // call toEquality on it: if ((result === "hello")(lowerCased.toEquality)) true else false
Trait providing an implicit class that adds a validating
method to
Future
, which takes one or more validation functions and returns either the
same Future
if either the Future
had already failed or its value
passes all the functions, or ValidationFailedException
containing an error message
describing the first validation that failed.
Trait providing an implicit class that adds a validating
method to
Future
, which takes one or more validation functions and returns either the
same Future
if either the Future
had already failed or its value
passes all the functions, or ValidationFailedException
containing an error message
describing the first validation that failed.
Here's an example validation method, which passes if the given Int
is evenly
divisible by 10 (i.e., the result will be Pass
). If the value does not pass
this test, the result is a Fail
containing a helpful error message string.
scala> import org.scalactic._ import org.scalactic._ scala> import FutureSugar._ import org.scalactic.FutureSugar._ scala> import scala.concurrent.Future import scala.concurrent.Future scala> import scala.concurrent.ExecutionContext.Implicits.global import scala.concurrent.ExecutionContext.Implicits.global scala> def isRound(i: Int): Validation[ErrorMessage] = | if (i % 10 == 0) Pass else Fail(i + " was not a round number") isRound: (i: Int)org.scalactic.Validation[org.scalactic.ErrorMessage]
Validation will be attempted on a successful Try
. If the validation succeeds, the
resulting Future
will be the same successful Future
with the same value. (A
"validation" only transforms the Future
if the validation fails, otherwise it is the
same Future
. The only difference is its value has now been proven valid.)
In the following example, a successful Future[Int]
with the value 100
passes the validation (which checks whether 100 is evenly divisible by 10), therefore
the result of the validating
call is the same successful Future
with the same value.
scala> val fut100 = Future(100) fut100: scala.concurrent.Future[Int] = scala.concurrent.impl.Promise$DefaultPromise@67f9c9c6 scala> fut100.value res0: Option[scala.util.Try[Int]] = Some(Success(100)) scala> val round100 = fut100.validating(isRound) round100: scala.concurrent.Future[Int] = scala.concurrent.impl.Promise$DefaultPromise@1ac2f0d1 scala> round100.value res1: Option[scala.util.Try[Int]] = Some(Success(100))
If validation fails, the successful Future
will be transformed into a failed one, with
a ValidationFailedException
that contains the error message
returned by the validation function. In the following example, 42 fails the validation because it
is not evenly divisible by 10:
scala> val fut42 = Future(42) fut42: scala.concurrent.Future[Int] = scala.concurrent.impl.Promise$DefaultPromise@19c6e4d1 scala> fut42.value res2: Option[scala.util.Try[Int]] = Some(Success(42)) scala> val round42 = fut42.validating(isRound) round42: scala.concurrent.Future[Int] = scala.concurrent.impl.Promise$DefaultPromise@b5175d scala> round42.value res3: Option[scala.util.Try[Int]] = Some(Failure(org.scalactic.exceptions.ValidationFailedException: 42 was not a round number))
If validating
is called on a failed Future
, it just returns the same failed Future
:
scala> val futEx = Future[Int] { throw new Exception("oops!") } futEx: scala.concurrent.Future[Int] = scala.concurrent.impl.Promise$DefaultPromise@3ba0299c scala> futEx.value res4: Option[scala.util.Try[Int]] = Some(Failure(java.lang.Exception: oops!)) scala> val roundEx = futEx.validating(isRound) roundEx: scala.concurrent.Future[Int] = scala.concurrent.impl.Promise$DefaultPromise@22bf1acf scala> roundEx.value res5: Option[scala.util.Try[Int]] = Some(Failure(java.lang.Exception: oops!))
The validating
method accepts one or more validation functions. If you
pass more than one, they will be tried in order up until the first failure, whose
error message will appear in the ValidationFailedException
. In other words,
validating
will short circuit at the first error and return that. It
will not accumulate errors. For example, the following validation will short circuit
after the isDivBy3
function fails:
scala> def isDivBy3(i: Int): Validation[ErrorMessage] = | if (i % 3 == 0) Pass else Fail(i + " was not divisible by 3") isDivBy3: (i: Int)org.scalactic.Validation[org.scalactic.ErrorMessage] scala> def isAnswerToLifeTheUniverseAndEverything(i: Int): Validation[ErrorMessage] = | if (i == 42) Pass else Fail(i + " did not equal 42") isAnswerToLifeTheUniverseAndEverything: (i: Int)org.scalactic.Validation[org.scalactic.ErrorMessage] scala> val futShort = fut100.validating(isRound, isDivBy3, isAnswerToLifeTheUniverseAndEverything) futShort: scala.concurrent.Future[Int] = scala.concurrent.impl.Promise$DefaultPromise@30bb943e scala> futShort.value res11: Option[scala.util.Try[Int]] = Some(Failure(org.scalactic.exceptions.ValidationFailedException: 100 was not divisible by 3))
Provides an implicit conversion that will be applied only if a higher-priority implicit conversion declared a subtrait is not applicable.
Provides an implicit conversion that will be applied only if a higher-priority implicit conversion declared a subtrait is not applicable.
The purpose of this trait is to make the ===
operator symetric. In other words, a ===
invocation
will be allowed if subtype relationship exists in either direction. For example, in the following expression, the left hand
side is a subtype of the right hand side:
List(1, 2, 3) === Seq(1, 2, 3)
But in the next expression, it the right hand side is a subtype of the left hand side
Seq(1, 2, 3) === List(1, 2, 3)
The first expression above is enabled by the implicit conversion typeCheckedConstraint
in trait
TypeCheckedTripleEquals
.
The second expression above is
enabled by the implicit conversion lowPriorityTypeCheckedConstraint
in this trait.
The reason these two implicit methods aren't both declared in the subtraits is that if the subtype relationship existed in both directions, they would conflict. This can happen when the exact same type is on both the left and right hand sides, because a type is a subtype of itself. By placing one of them in this supertrait, the higher priority conversion will be selected.
Provides an implicit method that loosens the equality constraint defined by TypeCheckedTripleEquals
or ConversionCheckedTripleEquals
for Scala Map
s to one that more closely matches Scala's approach to Map
equality.
Provides an implicit method that loosens the equality constraint defined by TypeCheckedTripleEquals
or ConversionCheckedTripleEquals
for Scala Map
s to one that more closely matches Scala's approach to Map
equality.
Scala's approach to Map
equality is that if both objects being compared are Map
s, the elements are compared to determine equality.
This means you could compare an immutable TreeMap
and a mutable HashMap
for equality, for instance, and get true so long as the two maps
contained the same key-value mappings. Here's an example:
scala> import scala.collection.immutable.TreeMap import scala.collection.immutable.TreeMap scala> import scala.collection.mutable.HashMap import scala.collection.mutable.HashMap scala> TreeMap("one" -> 1, "two" -> 2) == HashMap("one" -> 1, "two" -> 2) res0: Boolean = true
Such a comparison would not, however, compile if you used ===
under either TypeCheckedTripleEquals
or ConversionCheckedTripleEquals
,
because TreeMap
and HashMap
are not in a subtype/supertype relationship, nor does an implicit conversion by default exist between them:
scala> import org.scalactic._ import org.scalactic._ scala> import TypeCheckedTripleEquals._ import TypeCheckedTripleEquals._ scala> TreeMap("one" -> 1, "two" -> 2) === HashMap("one" -> 1, "two" -> 2) <console>:16: error: types scala.collection.immutable.TreeMap[String,Int] and scala.collection.mutable.HashMap[String,Int] do not adhere to the equality constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.EqualityConstraint[scala.collection.immutable.TreeMap[String,Int], scala.collection.mutable.HashMap[String,Int]] TreeMap("one" -> 1, "two" -> 2) === HashMap("one" -> 1, "two" -> 2) ^
If you mix or import the implicit conversion provided by MapEqualityConstraint
, however, the comparison will be allowed:
scala> import MapEqualityConstraints._ import MapEqualityConstraints._ scala> TreeMap("one" -> 1, "two" -> 2) === HashMap("one" -> 1, "two" -> 2) res2: Boolean = true
The equality constraint provided by this trait requires that both left and right sides are subclasses of scala.collection.GenMap
and that
an EqualityConstraint
can be found for both key types and both value types. In the example above, both the TreeMap
and
HashMap
are subclasses of scala.collection.GenMap
, and the regular TypeCheckedTripleEquals
provides equality
constraints for the key types, both of which are String
, and value types, both of which are Int
. By contrast, this
trait would not allow a TreeMap[String, Int]
to be compared against a HashMap[String, java.util.Date]
, because no equality constraint
will exist between the value types Int
and Date
:
scala> import java.util.Date import java.util.Date scala> TreeMap("one" -> 1, "two" -> 2) === HashMap("one" -> new Date, "two" -> new Date) <console>:20: error: types scala.collection.immutable.TreeMap[String,Int] and scala.collection.mutable.HashMap[String,java.util.Date] do not adhere to the equality constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.EqualityConstraint[scala.collection.immutable.TreeMap[String,Int], scala.collection.mutable.HashMap[String,java.util.Date]] TreeMap("one" -> 1, "two" -> 2) === HashMap("one" -> new Date, "two" -> new Date) ^
Provides an implicit conversion that allows norm
to be invoked on any value of type
T
for which an implicit Normalization[T]
exists.
Provides an implicit conversion that allows norm
to be invoked on any value of type
T
for which an implicit Normalization[T]
exists.
Here's an example:
scala> import org.scalactic._ import org.scalactic._ scala> import StringNormalizations._ import StringNormalizations._ scala> implicit val stringNormalization = lowerCased and trimmed stringNormalization: org.scalactic.Uniformity[String] = org.scalactic.Uniformity$$anon$1@19ba67ec scala> import NormMethods._ import NormMethods._ scala> val s = " There " s: String = " There " scala> "Hey " + s + "!" res5: String = Hey There ! scala> "Hey " + s.norm + "!" res6: String = Hey there!
Defines a custom way to normalize instances of a type.
Defines a custom way to normalize instances of a type.
For example, to normalize Double
s by truncating off any decimal part,
you might write:
import org.scalactic._ val truncated = new Normalization[Double] { def normalized(d: Double) = d.floor }
Given this definition you could use it with the Explicitly
DSL like this:
import org.scalatest._ import Matchers._ import TypeCheckedTripleEquals._ (2.1 should === (2.0)) (after being truncated)
Note that to use a Normalization
with the Explicitly
DSL, you'll need to use
TypeCheckedTripleEquals
.
If you're just using plain-old
TripleEquals
, you'll need a Uniformity
, a Normalization
subclass.
If you make the truncated
val
implicit and import or mix in the members of NormMethods
,
you can access the behavior by invoking .norm
on Double
s.
implicit val doubleNormalization = truncated import NormMethods._ val d = 2.1 d.norm // returns 2.0
the type whose normalization is being defined
An Equality[A]
implementation that determines the equality of two objects by normalizing
one or both objects, then comparing the results using an “after normalization” equality referenced from
the afterNormalizationEquality
member.
An Equality[A]
implementation that determines the equality of two objects by normalizing
one or both objects, then comparing the results using an “after normalization” equality referenced from
the afterNormalizationEquality
member. By default, the afterNormalizationEquality
is
an instance of Equality.default[A]
.
NormalizingEquality
is returned by the Explicitly
DSL's “after
being
”
syntax, using for the afterNormalizationEquality
the implicit Equality
in scope for the type
of Uniformity
passed to being
. Here's an example:
scala> import org.scalactic._ import org.scalactic._ scala> import Explicitly._ import Explicitly._ scala> import StringNormalizations._ import StringNormalizations._ scala> after being lowerCased res0: org.scalactic.NormalizingEquality[String] = ComposedNormalizingEquality(Equality.default,lowerCased)
An Equivalence[A]
implementation that determines the equality of two objects by normalizing
one or both objects, then comparing the results using an “after normalization” Equivalence
referenced from
the afterNormalizationEquivalence
member.
An Equivalence[A]
implementation that determines the equality of two objects by normalizing
one or both objects, then comparing the results using an “after normalization” Equivalence
referenced from
the afterNormalizationEquivalence
member. By default, the afterNormalizationEquivalence
is
an instance of Equivalence.default[A]
.
NormalizingEquivalence
is returned by the Explicitly
DSL's “after
being
”
syntax, using for the afterNormalizationEquivalence
the implicit Equivalence
in scope for the type
of Normalization
passed to being
. Here's an example:
scala> import org.scalactic._ import org.scalactic._ scala> import Explicitly._ import Explicitly._ scala> val lowerCased: Normalization[String] = StringNormalizations.lowerCased lowerCased: org.scalactic.Normalization[String] = lowerCased scala> after being lowerCased res0: org.scalactic.NormalizingEquivalence[String] = ComposedNormalizingEquivalence(Equality.default,lowerCased)
Trait providing an implicit class that adds a toOr
method to
Option
, which converts Some
to Good
,
None
to Bad
.
Trait providing an implicit class that adds a toOr
method to
Option
, which converts Some
to Good
,
None
to Bad
.
You can use the toOr
method to record information about why
a processing of nested Option
s resulted in None
.
For example, the following for
expression results in
None
if either the passed optional Person
is
None
or else if the contained optional age is None
:
scala> case class Person(name: String, age: Option[Int]) defined class Person scala> def ageOf(person: Option[Person]) = | for { | per <- person | age <- per.age | } yield age ageOf: (person: Option[Person])Option[Int] scala> ageOf(Some(Person("Ralph", Some(32)))) res0: Option[Int] = Some(32) scala> ageOf(Some(Person("Curt", None))) res3: Option[Int] = None scala> ageOf(None) res2: Option[Int] = None
If you instead populate the for
expression with Or
s,
supplying an error message or other "bad" value to the toOr
method
in case of None
, you'll get an indication of which part
failed if a None
is encountered:
scala> import OptionSugar._ import OptionSugar._ scala> def ageOf(person: Option[Person]) = | for { | per <- person toOr "no person here" | age <- per.age toOr "ageless person" | } yield age ageOf: (person: Option[Person])org.scalactic.Or[Int,String] scala> ageOf(Some(Person("Ralph", Some(32)))) res1: org.scalactic.Or[Int,String] = Good(32) scala> ageOf(Some(Person("Curt", None))) res2: org.scalactic.Or[Int,String] = Bad(ageless person) scala> ageOf(None) res3: org.scalactic.Or[Int,String] = Bad(no person here)
A function that given any object will produce a “pretty” string representation of that object, where “pretty” is in the eye of the implementer.
A function that given any object will produce a “pretty” string representation of that object, where “pretty” is in the eye of the implementer.
Scala's Any
type declares a toString
that will convert any object to a String
representation. This String
representation is primarily intended for programmers, and is usually sufficient.
However, sometimes it can be helpful to provide an alternative implementation of toString
for certain types.
For example, the toString
implementation on String
prints out the value of the String
:
scala> "1".toString res0: String = 1
If the error message that resulted from comparing Int
1 with String
"1"
in a ScalaTest assertion used toString
, therefore, the error message would be:
1 did not equal 1
To make it quicker to figure out why the assertion failed, ScalaTest prettifies the objects involved in
the error message. The default Prettifier
will place double quotes on either side of a String
s
toString
result:
scala> import org.scalactic._ import org.scalactic._ scala> Prettifier.default("1") res1: String = "1"
Thus the error message resulting from comparing Int
1 with String
"1"
,
in a ScalaTest assertion is:
1 did not equal "1"
If you wish to prettify an object in production code, for example, to issue a profoundly clear debug message, you can use
PrettyMethods
and invoke pretty
. Here's an example:
scala> import PrettyMethods._ import PrettyMethods._ scala> 1.pretty res2: String = 1 scala> "1".pretty res3: String = "1"
For example, the default Prettifier
, `Prettifier.default`, transforms:
Null
to: null
Unit
to: <() the Unit value>
String
to: "string"
(the toString
result surrounded by double quotes)Char
to: 'c'
(the toString
result surrounded by single quotes)Array
to: Array("1", "2", "3")
scala.Some
to: Some("3")
scala.util.Left
to: Left("3")
scala.util.Right
to: Right("3")
scala.util.Success
to: Success("3")
org.scalactic.Good
to: Good("3")
org.scalactic.Bad
to: Bad("3")
org.scalactic.One
to: One("3")
org.scalactic.Many
to: Many("1", "2", "3")
scala.collection.GenTraversable
to: List("1", "2", "3")
java.util.Collection
to: ["1", "2", "3"]
java.util.Map
to: {1="one", 2="two", 3="three"}
For anything else, the default Prettifier
returns the result of invoking toString
.
Note: Prettifier
is not parameterized (i.e., Prettifier[T]
, where T
is the type
to prettify) because assertions (including matcher expressions) in ScalaTest would then need to look up Prettifier
s implicitly by type. This would slow
compilation even though most (let's guess 99.9%) of the time in practice assertions do not fail, and thus 99.9% of the time no error messages need to be generated.
If no error messages are needed 99.9% of the time, no prettification is needed 99.9% of the time, so the slow down in compile time for the implicit
look ups is unlikely to be worth the benefit. Only a few types in practice usually need prettification for testing error message purposes, and those will be covered
by the default Prettifier
. A future version of ScalaTest will provide a simple mechanism to replace the default Prettifier
with a
custom one when a test actually fails.
Provides an implicit conversion that enables pretty
to be invoked on any
object, to transform that object into a String
representation.
Provides an implicit conversion that enables pretty
to be invoked on any
object, to transform that object into a String
representation.
Trait that contains require
, and requireState
, and requireNonNull
methods for checking pre-conditions
that give descriptive error messages extracted via a macro.
Trait that contains require
, and requireState
, and requireNonNull
methods for checking pre-conditions
that give descriptive error messages extracted via a macro.
These methods of trait Requirements
aim to improve error messages provided when a pre-condition check fails at runtime in
production code. Although it is recommended practice to supply helpful error messages when doing pre-condition checks, often people
don't. Instead of this:
scala> val length = 5 length: Int = 5 scala> val idx = 6 idx: Int = 6 scala> require(idx >= 0 && idx <= length, "index, " + idx + ", was less than zero or greater than or equal to length, " + length) java.lang.IllegalArgumentException: requirement failed: index, 6, was less than zero or greater than or equal to length, 5 at scala.Predef$.require(Predef.scala:233) ...
People write simply:
scala> require(idx >= 0 && idx <= length) java.lang.IllegalArgumentException: requirement failed at scala.Predef$.require(Predef.scala:221) ...
Note that the detail message of the IllegalArgumentException
thrown by the previous line of code is simply, "requirement failed"
.
Such messages often end up in a log file or bug report, where a better error message can save time in debugging the problem.
By importing the members of Requirements
(or mixing in its companion trait), you'll get a more helpful error message
extracted by a macro, whether or not a clue message is provided:
scala> import org.scalactic._ import org.scalactic._ scala> import Requirements._ import Requirements._ scala> require(idx >= 0 && idx <= length) java.lang.IllegalArgumentException: 6 was greater than or equal to 0, but 6 was not less than or equal to 5 at org.scalactic.Requirements$RequirementsHelper.macroRequire(Requirements.scala:56) ... scala> require(idx >= 0 && idx <= length, "(hopefully that helps)") java.lang.IllegalArgumentException: 6 was greater than or equal to 0, but 6 was not less than or equal to 5 (hopefully that helps) at org.scalactic.Requirements$RequirementsHelper.macroRequire(Requirements.scala:56) ...
The requireState
method provides identical error messages to require
, but throws
IllegalStateException
instead of IllegalArgumentException
:
scala> val connectionOpen = false connectionOpen: Boolean = false scala> requireState(connectionOpen) java.lang.IllegalStateException: connectionOpen was false at org.scalactic.Requirements$RequirementsHelper.macroRequireState(Requirements.scala:71) ...
Thus, whereas the require
methods throw the Java platform's standard exception indicating a passed argument
violated a precondition, IllegalArgumentException
, the requireState
methods throw the standard
exception indicating an object's method was invoked when the object was in an inappropriate state for that method,
IllegalStateException
.
The requireNonNull
method takes one or more variables as arguments and throws NullArgumentException
with an error messages that includes the variable names if any are null
. Here's an example:
scala> val e: String = null e: String = null scala> val f: java.util.Date = null f: java.util.Date = null scala> requireNonNull(a, b, c, d, e, f) org.scalactic.exceptions.NullArgumentException: e and f were null at org.scalactic.Requirements$RequirementsHelper.macroRequireNonNull(Requirements.scala:101) ...
Although trait Requirements
can help you debug problems that occur in production, bear in mind that a much
better alternative is to make it impossible for such events to occur at all. Use the type system to ensure that all
pre-conditions are met so that the compiler can find broken pre-conditions and point them out with compiler error messages.
When this is not possible or practical, however, trait Requirements
is helpful.
Provides an implicit method that loosens the equality constraint defined by TypeCheckedTripleEquals
or ConversionCheckedTripleEquals
for Scala Seq
s to one that more closely matches Scala's approach to Seq
equality.
Provides an implicit method that loosens the equality constraint defined by TypeCheckedTripleEquals
or ConversionCheckedTripleEquals
for Scala Seq
s to one that more closely matches Scala's approach to Seq
equality.
Scala's approach to Seq
equality is that if both objects being compared are Seq
s, the elements are compared to determine equality.
This means you could compare an immutable Vector
and a mutable ListBuffer
for equality, for instance, and get true so long as the
two Seq
s contained the same elements in the same order. Here's an example:
scala> import scala.collection.mutable.ListBuffer import scala.collection.mutable.ListBuffer scala> Vector(1, 2) == ListBuffer(1, 2) res0: Boolean = true
Such a comparison would not, however, compile if you used ===
under either TypeCheckedTripleEquals
or ConversionCheckedTripleEquals
,
because Vector
and ListBuffer
are not in a subtype/supertype relationship, nor does an implicit conversion by default exist between them:
scala> import org.scalactic._ import org.scalactic._ scala> import TypeCheckedTripleEquals._ import TypeCheckedTripleEquals._ scala> Vector(1, 2) === ListBuffer(1, 2) <console>:16: error: types scala.collection.immutable.Vector[Int] and scala.collection.mutable.ListBuffer[Int] do not adhere to the equality constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.EqualityConstraint[scala.collection.immutable.Vector[Int], scala.collection.mutable.ListBuffer[Int]] Vector(1, 2) === ListBuffer(1, 2) ^
If you mix or import the implicit conversion provided by SeqEqualityConstraint
, however, the comparison will be allowed:
scala> import SeqEqualityConstraints._ import SeqEqualityConstraints._ scala> Vector(1, 2) === ListBuffer(1, 2) res2: Boolean = true
The equality constraint provided by this trait requires that both left and right sides are subclasses of scala.collection.GenSeq
and that
an EqualityConstraint
can be found for the element types. In the example above, both the Vector
and
ListBuffer
are subclasses of scala.collection.GenSeq
, and the regular TypeCheckedTripleEquals
provides equality
constraints for the element types, both of which are Int
. By contrast, this
trait would not allow a Vector[Int]
to be compared against a ListBuffer[java.util.Date]
, because no equality constraint
will exist between the element types Int
and Date
:
scala> import java.util.Date import java.util.Date scala> Vector(1, 2) === ListBuffer(new Date, new Date) <console>:20: error: types scala.collection.immutable.Vector[Int] and scala.collection.mutable.ListBuffer[java.util.Date] do not adhere to the equality constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.EqualityConstraint[scala.collection.immutable.Vector[Int], scala.collection.mutable.ListBuffer[java.util.Date]] Vector(1, 2) === ListBuffer(new Date, new Date) ^
Provides an implicit method that loosens the equality constraint defined by TypeCheckedTripleEquals
or ConversionCheckedTripleEquals
for Scala Set
s to one that more closely matches Scala's approach to Set
equality.
Provides an implicit method that loosens the equality constraint defined by TypeCheckedTripleEquals
or ConversionCheckedTripleEquals
for Scala Set
s to one that more closely matches Scala's approach to Set
equality.
Scala's approach to Set
equality is that if both objects being compared are Set
s, the elements are compared to determine equality.
This means you could compare an immutable TreeSet
and a mutable HashSet
for equality, for instance, and get true so long as the
two Set
s contained the same elements in the same order. Here's an example:
scala> import scala.collection.immutable.TreeSet import scala.collection.immutable.TreeSet scala> import scala.collection.mutable.HashSet import scala.collection.mutable.HashSet scala> TreeSet(1, 2) == HashSet(1, 2) res0: Boolean = true
Such a comparison would not, however, compile if you used ===
under either TypeCheckedTripleEquals
or ConversionCheckedTripleEquals
,
because TreeSet
and HashSet
are not in a subtype/supertype relationship, nor does an implicit conversion by default exist between them:
scala> import org.scalactic._ import org.scalactic._ scala> import TypeCheckedTripleEquals._ import TypeCheckedTripleEquals._ scala> TreeSet(1, 2) === HashSet(1, 2) <console>:16: error: types scala.collection.immutable.TreeSet[Int] and scala.collection.mutable.HashSet[Int] do not adhere to the equality constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.EqualityConstraint[scala.collection.immutable.TreeSet[Int], scala.collection.mutable.HashSet[Int]] TreeSet(1, 2) === HashSet(1, 2) ^
If you mix or import the implicit conversion provided by SetEqualityConstraint
, however, the comparison will be allowed:
scala> import SetEqualityConstraints._ import SetEqualityConstraints._ scala> TreeSet(1, 2) === HashSet(1, 2) res2: Boolean = true
The equality constraint provided by this trait requires that both left and right sides are subclasses of scala.collection.GenSet
and that
an EqualityConstraint
can be found for the element types. In the example above, both the TreeSet
and
HashSet
are subclasses of scala.collection.GenSet
, and the regular TypeCheckedTripleEquals
provides equality
constraints for the element types, both of which are Int
. By contrast, this
trait would not allow a TreeSet[Int]
to be compared against a HashSet[java.util.Date]
, because no equality constraint
will exist between the element types Int
and Date
:
scala> import java.util.Date import java.util.Date scala> TreeSet(1, 2) === HashSet(new Date, new Date) <console>:20: error: types scala.collection.immutable.TreeSet[Int] and scala.collection.mutable.HashSet[java.util.Date] do not adhere to the equality constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.EqualityConstraint[scala.collection.immutable.TreeSet[Int], scala.collection.mutable.HashSet[java.util.Date]] TreeSet(1, 2) === HashSet(new Date, new Date) ^
Case class that stores the name and value of a variable or expression.
Case class that stores the name and value of a variable or expression.
See the main documentation for trait Snapshots
for more information and examples.
the name of the expression
the value of the expression
An IndexedSeq[Snapshot]
providing toString
and lines
methods that
can be useful for debug and log messages about program state.
An IndexedSeq[Snapshot]
providing toString
and lines
methods that
can be useful for debug and log messages about program state.
See the main documentation for trait Snapshots
for more information and examples.
Trait that provides a snap
method that takes one or more arguments and results in a
SnapshotSeq
, whose toString
lists the names
and values of each argument.
Trait that provides a snap
method that takes one or more arguments and results in a
SnapshotSeq
, whose toString
lists the names
and values of each argument.
The intended use case of this trait is to help you write debug and log messages that give a "snapshot" of program state. Here's an example:
scala> import Snapshots._ import Snapshots._ scala> snap(a, b, c, d, e, f) res3: org.scalactic.SnapshotSeq = a was 1, b was 2, c was 3, d was 4, e was null, f was null
SnapshotSeq
offers a lines
method that places each variable name/value pair on its own line:
scala> snap(a, b, c, d, e, f).lines res4: String = a was 1 b was 2 c was 3 d was 4 e was null f was null
Or, because a SnapshotSeq
is a IndexedSeq[Snapshot]
, you can process it just like any other Seq
, for example:
scala> snap(a, b, c, d, e, f).mkString("Wow! ", ", and ", ". That's so awesome!") res6: String = Wow! a was 1, and b was 2, and c was 3, and d was 4, and e was null, and f was null. That's so awesome!
Provides methods that produce Uniformity[String]
instances for various
ways to normalize strings for equality comparisons.
Provides methods that produce Uniformity[String]
instances for various
ways to normalize strings for equality comparisons.
Trait providing an implicit conversion that adds a times
method to Int
s that
will repeat a given side-effecting operation multiple times.
Trait providing an implicit conversion that adds a times
method to Int
s that
will repeat a given side-effecting operation multiple times.
Here's an example in which a friendly greeting is printed three times:
3 times println("Hello again, world!")
Running the above code would yield this output:
Hello again, world! Hello again, world! Hello again, world!
If you need to repeat a block of statements multiple times, just enclose them in parentheses, like this:
2 times { print("Hello ") print("again, ") println("world!") }
Running the above code would yield:
Hello again, world! Hello again, world!
This trait enables times
to be invoked on 0 and any positive integer,
but attempting to invoke times
on a negative integer will result in an IllegalArgumentException
.
Trait containing an implicit conversion that adds a +-
method to Numeric
types, which enables
spreads to be expressed in terms of a pivot and tolerance.
Trait containing an implicit conversion that adds a +-
method to Numeric
types, which enables
spreads to be expressed in terms of a pivot and tolerance.
For example, the TripleEquals
trait (and its type-checking siblings TypeCheckedTripleEquals
and
ConversionCheckedTripleEquals
) enable you to write:
a === (1.0 +- 0.1)
Provides Equality
and Equivalence
instances for Numeric
types that
compare for equality with a given tolerance.
Provides Equality
and Equivalence
instances for Numeric
types that
compare for equality with a given tolerance.
Here's an example:
scala> import org.scalactic._ import org.scalactic._ scala> import TripleEquals._ import TripleEquals._ scala> 2.001 === 2.0 res0: Boolean = false scala> implicit val doubleEquality = TolerantNumerics.tolerantDoubleEquality(0.01) doubleEquality: org.scalactic.Equality[Double] = org.scalactic.TolerantNumerics$$anon$1@16c2bd13 scala> 2.001 === 2.0 res1: Boolean = true
Provides three implicit methods that loosen the equality constraint defined by TypeCheckedTripleEquals
for Scala Traversable
s to one that more closely matches Scala's approach to Traversable
equality.
Provides three implicit methods that loosen the equality constraint defined by TypeCheckedTripleEquals
for Scala Traversable
s to one that more closely matches Scala's approach to Traversable
equality.
Scala's approach to Traversable
equality is that if the objects being compared are ether both Seq
s, both Set
s,
or both Map
s, the elements are compared to determine equality.
This means you could compare an immutable Vector
and a mutable ListBuffer
for equality, for instance, and get true so long as the
two Seq
s contained the same elements in the same order. Here's an example:
scala> import scala.collection.mutable.ListBuffer import scala.collection.mutable.ListBuffer scala> Vector(1, 2) == ListBuffer(1, 2) res0: Boolean = true
Such a comparison would not, however, compile if you used ===
under TypeCheckedTripleEquals
,
because Vector
and ListBuffer
are not in a subtype/supertype relationship:
scala> import org.scalactic._ import org.scalactic._ scala> import TypeCheckedTripleEquals._ import TypeCheckedTripleEquals._ scala> Vector(1, 2) === ListBuffer(1, 2) <console>:16: error: types scala.collection.immutable.Vector[Int] and scala.collection.mutable.ListBuffer[Int] do not adhere to the equality constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.CanEqual[scala.collection.immutable.Vector[Int], scala.collection.mutable.ListBuffer[Int]] Vector(1, 2) === ListBuffer(1, 2) ^
If you mix or import the implicit conversion provided by TraversableEqualityConstraint
, however, the comparison will be allowed:
scala> import TraversableEqualityConstraints._ import TraversableEqualityConstraints._ scala> Vector(1, 2) === ListBuffer(1, 2) res2: Boolean = true
The equality constraints provided by this trait require that left and right sides are both subclasses of either scala.collection.GenSeq
,
scala.collection.GenSet
, or scala.collection.GenMap
, and that
an CanEqual
can be found for the element types for Seq
and Set
, or the key and value types for Map
s. In
the example above, both the Vector
and
ListBuffer
are subclasses of scala.collection.GenSeq
, and the regular TypeCheckedTripleEquals
provides equality
constraints for the element types, both of which are Int
. By contrast, this
trait would not allow a Vector[Int]
to be compared against a ListBuffer[java.util.Date]
, because no equality constraint
will exist between the element types Int
and Date
:
scala> import java.util.Date import java.util.Date scala> Vector(1, 2) === ListBuffer(new Date, new Date) <console>:20: error: types scala.collection.immutable.Vector[Int] and scala.collection.mutable.ListBuffer[java.util.Date] do not adhere to the equality constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.CanEqual[scala.collection.immutable.Vector[Int], scala.collection.mutable.ListBuffer[java.util.Date]] Vector(1, 2) === ListBuffer(new Date, new Date) ^
This trait simply mixes together SeqEqualityConstraints
,
SetEqualityConstraints
,
and MapEqualityConstraints
.
Provides ===
and !==
operators that return Boolean
, delegate the equality determination
to an Equality
type class, and require no relationship between the types of the two values compared.
Provides ===
and !==
operators that return Boolean
, delegate the equality determination
to an Equality
type class, and require no relationship between the types of the two values compared.
Recommended Usage:
Trait TripleEquals is useful (in both production and test code) when you need determine equality for a type of object differently than its
equals method: either you can't change the equals method, or the equals method is sensible generally, but
you are in a special situation where you need something else. You can use the SuperSafe Community Edition compiler plugin to
get a compile-time safety check of types being compared with === . In situations where you need a stricter type check, you can use
TypeCheckedTripleEquals .
|
This trait will override or hide implicit methods defined by its sibling trait,
TypeCheckedTripleEquals
,
and can therefore be used to temporarily turn of type checking in a limited scope. Here's an example, in which TypeCheckedTripleEquals
will
cause a compiler error:
import org.scalactic._ import TypeCheckedTripleEquals._ object Example { def cmp(a: Int, b: Long): Int = { if (a === b) 0 // This line won't compile else if (a < b) -1 else 1 } def cmp(s: String, t: String): Int = { if (s === t) 0 else if (s < t) -1 else 1 } }
Because Int
and Long
are not in a subtype/supertype relationship, comparing 1
and 1L
in the context
of TypeCheckedTripleEquals
will generate a compiler error:
Example.scala:9: error: types Int and Long do not adhere to the equality constraint selected for the === and !== operators; they must either be in a subtype/supertype relationship; the missing implicit parameter is of type org.scalactic.Constraint[Int,Long] if (a === b) 0 // This line won't compile ^ one error found
You can “turn off” the type checking locally by importing the members of TripleEquals
in
a limited scope:
package org.scalactic.examples.tripleequals import org.scalactic._ import TypeCheckedTripleEquals._ object Example { def cmp(a: Int, b: Long): Int = { import TripleEquals._ if (a === b) 0 else if (a < b) -1 else 1 } def cmp(s: String, t: String): Int = { if (s === t) 0 else if (s < t) -1 else 1 } }
With the above change, the Example.scala
file compiles fine. Type checking is turned off only inside the first cmp
method that
takes an Int
and a Long
. TypeCheckedTripleEquals
is still enforcing its type constraint, for example, for the s === t
expression in the other overloaded cmp
method that takes strings.
Because the methods in TripleEquals
(and its siblings)override all the methods defined in
supertype TripleEqualsSupport
, you can achieve the same
kind of nested tuning of equality constraints whether you mix in traits, import from companion objects, or use some combination of both.
In short, you should be able to select a primary constraint level via either a mixin or import, then change that in nested scopes however you want, again either through a mixin or import, without getting any implicit conversion ambiguity. The innermost constraint level in scope will always be in force.
Trait that defines abstract methods used to enforce compile-time type constraints for equality comparisons, and defines ===
and !==
operators
used by matchers.
Trait that defines abstract methods used to enforce compile-time type constraints for equality comparisons, and defines ===
and !==
operators
used by matchers.
The abstract methods of this trait are selectively implemented as implicit by subclasses to enable a spectrum of type constraints for the
===
and !==
operators. As an illustration, if in the expression, a === b
, the type of a
is A
and b
is B
, the following three levels of compile-time checking can be obtained from
TripleEqualsSupport
subtraits:
Unchecked - A
and B
can be any two types. This constraint level is available from
subtrait TripleEquals
.
Statically-checked - A
must be a subtype of B
, or vice versa, or must cooperate such that the
equality laws stated in the equals
contract are preserved.
This (intermediate) constraint level is available by using subtrait TripleEquals
and installing the SuperSafe Community Edition
Scala compiler plugin.
Type-checked - A
must be a subtype of B
, or vice versa.
(Both A
and B
can be the same type, because a type is considered a subtype
of itself.)
This (strongest) constraint level is available from subtrait TypeCheckedTripleEquals
.
This trait defines all methods that need to be defined implicitly by the subtraits so that if multiple subtraits are used together, the inner-most
subtrait in scope can not only enable the implicits it needs by overriding or hiding those methods (currently-in-scope as regular, non-implicit
methods) and making
them implicit, it can also disable any implicits enabled by its sibling subtraits in enclosing scopes. For example, if your test class mixes
in TypeCheckedTripleEquals
, inside your test class the following methods will be implicit:
convertToCheckingEqualizer
typeCheckedConstraint
lowPriorityTypeCheckedConstraint
convertEquivalenceToAToBConstraint
convertEquivalenceToBToAConstraint
If in the body of a test you want to turn off the type checking, you can import the members
of TripleEquals
in the body of that test. This will not only hide
non-implicit methods convertToEqualizer
unconstrainedEquality
of TypeCheckedTripleEquals
,
replacing those with implicit ones defined in TripleEquals
, it will also hide the three methods made implicit in TypeCheckedTripleEquals
(and listed above), replacing them by non-implicit ones.
In short, you should be able to select a primary constraint level via either a mixin or import, then change that in nested scopes however you want, again either through a mixin or import, without getting any implicit conversion ambiguity. The innermost constraint level in scope will always be in force.
Trait providing an implicit class that adds a toOr
method to
Try
, which converts Success
to Good
,
and Failure
to Bad
, as well as a validating
method,
which takes one or more validation functions and returns either the
same Try
if either the Try
had already failed or its value
passes all the functions, or ValidationFailedException
containing an error message
describing the first validation that failed.
Trait providing an implicit class that adds a toOr
method to
Try
, which converts Success
to Good
,
and Failure
to Bad
, as well as a validating
method,
which takes one or more validation functions and returns either the
same Try
if either the Try
had already failed or its value
passes all the functions, or ValidationFailedException
containing an error message
describing the first validation that failed.
Here's an example validation method, which passes if the given Int
is evenly
divisible by 10 (i.e., the result will be Pass
). If the value does not pass
this test, the result is a Fail
containing a helpful error message string.
scala> import org.scalactic._ import org.scalactic._ scala> import TrySugar._ import TrySugar._ scala> import scala.util.Try import scala.util.Try scala> def isRound(i: Int): Validation[ErrorMessage] = | if (i % 10 == 0) Pass else Fail(i + " was not a round number") isRound: (i: Int)org.scalactic.Validation[org.scalactic.ErrorMessage]
Validation will be attempted on a successful Try
. If the validation succeeds, the
resulting Try
will be the same successful Try
with the same value. (A
"validation" only transforms the Try
if the validation fails, otherwise it is the
same Try
. The only difference is its value has now been proven valid.)
In the following example, a successful Try[Int]
with the value 100
passes the validation (which checks whether 100 is evenly divisible by 10), therefore
the result of the validating
call is the same successful Try
with the same value.
scala> val try100 = Try(100) try100: scala.util.Try[Int] = Success(100) scala> val round100 = try100.validating(isRound) round100: scala.util.Try[Int] = Success(100)
If validation fails, the successful Try
will be transformed into a failed one, with
a ValidationFailedException
that contains the error message
returned by the validation function. In the following example, 42 fails the validation because it
is not evenly divisible by 10:
scala> val try42 = Try(42) try42: scala.util.Try[Int] = Success(42) scala> val round42 = try42.validating(isRound) round42: scala.util.Try[Int] = Failure(org.scalactic.exceptions.ValidationFailedException: 42 was not a round number)
If validating
is called on a failed Try
, it just returns the same failed Try
:
scala> val tryEx = Try[Int] { throw new Exception("oops!") } tryEx: scala.util.Try[Int] = Failure(java.lang.Exception: oops!) scala> val roundEx = tryEx.validating(isRound) roundEx: scala.util.Try[Int] = Failure(java.lang.Exception: oops!)
The validating
method accepts one or more validation functions. If you
pass more than one, they will be tried in order up until the first failure, whose
error message will appear in the ValidationFailedException
. In other words,
validating
will short circuit at the first error and return that. It
will not accumulate errors. For example, the following validation will short circuit
after the isDivBy3
function fails:
scala> def isDivBy3(i: Int): Validation[ErrorMessage] = | if (i % 3 == 0) Pass else Fail(i + " was not divisible by 3") isDivBy3: (i: Int)org.scalactic.Validation[org.scalactic.ErrorMessage] scala> def isAnswerToLifeTheUniverseAndEverything(i: Int): Validation[ErrorMessage] = | if (i == 42) Pass else Fail(i + " did not equal 42") isAnswerToLifeTheUniverseAndEverything: (i: Int)org.scalactic.Validation[org.scalactic.ErrorMessage] scala> try100.validating(isRound, isDivBy3, isAnswerToLifeTheUniverseAndEverything) res0: scala.util.Try[Int] = Failure(org.scalactic.exceptions.ValidationFailedException: 100 was not divisible by 3)
Here are some examples of the toOr
method:
scala> try100.toOr res1: org.scalactic.Or[Int,Throwable] = Good(100) scala> tryEx.toOr res2: org.scalactic.Or[Int,Throwable] = Bad(java.lang.Exception: oops!)
Provides ===
and !==
operators that return Boolean
, delegate the equality determination
to an Equality
type class, and require the types of the two values compared to be in a subtype/supertype
relationship.
Provides ===
and !==
operators that return Boolean
, delegate the equality determination
to an Equality
type class, and require the types of the two values compared to be in a subtype/supertype
relationship.
Recommended Usage:
Trait TypeCheckedTripleEquals is useful (in both production and test code) when you need a stricter type check
than is provided by the SuperSafe Community Edition compiler plugin for
TripleEquals . For example, if you are developing a library that uses advanced
features of Scala's type system, you may want to enforce in your tests that the types appearing
in equality comparisons match exactly.
|
By default under TripleEquals
, any use of ===
will compile, just like the ==
operator:
scala> import org.scalactic._ import org.scalactic._ scala> import TripleEquals._ import TripleEquals._ scala> 1L === 1 // A Long can equal an Int res0: Boolean = true scala> List(1, 2, 3) === Vector(1, 2, 3) // A List can equal a Vector res1: Boolean = true scala> "hi" === 1 // Likely a bug, because a String can never equal an Int res2: Boolean = false
With SuperSafe Community Edition installed, the first two expressions above will be allowed to compile, but the third (which represents a likely bug) will not:
scala> import org.scalactic._ import org.scalactic._ scala> import TripleEquals._ import TripleEquals._ scala> 1L === 1 res0: Boolean = true scala> List(1, 2, 3) === Vector(1, 2, 3) res1: Boolean = true scala> "hi" === 1 // SuperSafe catches the bug at compile time <console>:17: error: [Artima SuperSafe] Values of type String and Int may not be compared with the === operator. If you really want to compare them for equality, configure Artima SuperSafe to allow those types to be compared for equality. For more information on this kind of error, see: http://www.artima.com/supersafe_user_guide.html#safer-equality "hi" === 1 ^
By contrast, TypeCheckedTripleEquals
will prevent any of the above three expressions from compiling:
scala> import org.scalactic._ import org.scalactic._ scala> import TypeCheckedTripleEquals._ import TypeCheckedTripleEquals._ scala> 1L === 1 <console>:17: error: types Long and Int do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.CanEqual[Long,Int] 1L === 1 ^ scala> List(1, 2, 3) === Vector(1, 2, 3) <console>:17: error: types List[Int] and scala.collection.immutable.Vector[Int] do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.CanEqual[List[Int],scala.collection.immutable.Vector[Int]] List(1, 2, 3) === Vector(1, 2, 3) ^ scala> "hi" === 1 <console>:17: error: types String and Int do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.CanEqual[String,Int] "hi" === 1 ^
Trait TypeCheckedTripleEquals
rejects comparisons of types Int
and Long
, List[Int]
and Vector[Int]
, and String
and Int
, because none have a direct subtype/supertype relationship.
To compare two types that are unrelated by inheritance under TypeCheckedTripleEquals
, you could
convert one of them to the other type (because a type is both a subtype and supertype of itself). Here's an example:
scala> 1L === 1.toLong // Now both sides are Long res0: Boolean = true scala> List(1, 2, 3) === Vector(1, 2, 3).toList // Now both sides are List[Int] res1: Boolean = true
Nevertheless, a better (and the recommended) way to deal with this situation is to use a widening type ascription.
A type ascription is simply a colon and a type placed next to a variable, usually surrounded by parentheses.
For example, because AnyVal
is a common supertype of Int
and Long
,
you could solve the type error by widening the type of one side or the other to AnyVal
.
Because AnyVal
is a supertype of both Int
and Long
, the
type constraint will be satisfied:
scala> 1 === (1L: AnyVal) res2: Boolean = true scala> (1: AnyVal) === 1L res3: Boolean = true
Similarly, since Seq[Int]
is a common supertype of both
Vector[Int]
and List[Int]
, the type constraint can be
satisfied by widening either to their common supertype, Seq[Int]
:
scala> List(1, 2, 3) === (Vector(1, 2, 3): Seq[Int]) res4: Boolean = true scala> (List(1, 2, 3): Seq[Int]) === Vector(1, 2, 3) res5: Boolean = true
The primary intended use case for TypeCheckedTripleEquals
is to enable tests to be very strict
about which types can compared for equality, but it can also be used with production code where this level of
strictness is desired.
You can also use a type ascription to force an implicit conversion before a value participates
in an equality comparison. For example, although JavaConversions
provides
an implicit conversion between java.util.Set
and scala.collection.mutable.Set
,
under TypeCheckedTripleEquals
an equality comparison between those two types
will not be allowed:
scala> import collection.JavaConversions._ import collection.JavaConversions._ scala> import collection.mutable import collection.mutable scala> import TypeCheckedTripleEquals._ import TypeCheckedTripleEquals._ scala> mutable.Set.empty[String] === new java.util.HashSet[String] <console>:36: error: types scala.collection.mutable.Set[String] and java.util.HashSet[String] do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.CanEqual[scala.collection.mutable.Set[String],java.util.HashSet[String]] mutable.Set.empty[String] === new java.util.HashSet[String] ^
To force an implicit conversion of the Java HashSet
to a Scala mutable.Set
, after which the
type constraint will be satisfied, you can use a type ascription:
scala> mutable.Set.empty[String] === (new java.util.HashSet[String]: mutable.Set[String]) res0: Boolean = true
This trait will override or hide implicit methods defined by
TripleEquals
and can therefore be used to temporarily turn on or off type checking in a limited scope. Here's an example, in which TypeCheckedTripleEquals
will
cause a compiler error:
import org.scalactic._ import TypeCheckedTripleEquals._ object Example { def cmp(a: Int, b: Long): Int = { if (a === b) 0 // This line won't compile else if (a < b) -1 else 1 } def cmp(s: String, t: String): Int = { if (s === t) 0 else if (s < t) -1 else 1 } }
Because Int
and Long
are not in a subtype/supertype relationship, comparing 1
and 1L
in the context
of TypeCheckedTripleEquals
will generate a compiler error:
Example.scala:9: error: types Int and Long do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.CanEqual[Int,Long] if (a === b) 0 // This line won't compile ^ one error found
You can “relax” the type checking locally by importing
the members of TripleEquals
in a limited scope:
package org.scalactic.examples.conversioncheckedtripleequals import org.scalactic._ import TypeCheckedTripleEquals._ object Example { def cmp(a: Int, b: Long): Int = { import TripleEquals._ if (a === b) 0 else if (a < b) -1 else 1 } def cmp(s: String, t: String): Int = { if (s === t) 0 else if (s < t) -1 else 1 } }
With the above change, the Example.scala
file compiles fine. The strict checking is disabled only inside the first cmp
method that
takes an Int
and a Long
. TypeCheckedTripleEquals
is still enforcing its type constraint, for example, for the s === t
expression in the other overloaded cmp
method that takes strings.
Because the methods TripleEquals
and TypeCheckedTripleEquals
override all the methods defined in supertype TripleEqualsSupport
, you can achieve the same
kind of nested tuning of equality constraints whether you mix in traits, import from companion objects, or use some combination of both.
In short, you should be able to select a primary constraint level via either a mixin or import, then change that in nested scopes however you want, again either through a mixin or import, without getting any implicit conversion ambiguity. The innermost constraint level in scope will always be in force.
Defines a custom way to normalize instances of a type that can also handle normalization of that type when passed as Any
.
Defines a custom way to normalize instances of a type that can also handle normalization of that type when passed as Any
.
For example, to normalize Double
s by truncating off any decimal part,
you might write:
import org.scalactic._ val truncated = new Uniformity[Double] { def normalized(d: Double) = d.floor def normalizedCanHandle(o: Any) = o.isInstanceOf[Double] def normalizedOrSame(o: Any): Any = o match { case d: Double => normalized(d) case _ => o } }
Given this definition you could use it with the Explicitly
DSL like this:
import org.scalatest._ import Matchers._ 2.1 should equal (2.0) (after being truncated)
If you make the truncated
val
implicit and import or mix in the members of NormMethods
,
you can access the behavior by invoking .norm
on Double
s.
implicit val doubleUniformity = truncated import NormMethods._ val d = 2.1 d.norm // returns 2.0
Note that by creating a Uniformity
rather than just an instance of its supertype, Normalization
,
it can be used more generally. For example, Uniformity
s allow you to the Explicitly
DSL with
TripleEquals
, whereas Normalization
s require
TypeCheckedTripleEquals
.
Uniformity
s also enable you to use the Explicitly
DSL with ScalaTest's should
===
, equal
,
and contain
matcher syntax, whereas a plain Normalization
can only be used with should
===
, and only
under TypeCheckedTripleEquals
.
the type whose uniformity is being defined
The name org.scalactic.Chain
has been deprecated and will be removed in a future version of Scalactic. Please use
its new name, org.scalatest.anyvals.NonEmptyList
, instead.
The name org.scalactic.Chain
has been deprecated and will be removed in a future version of Scalactic. Please use
its new name, org.scalatest.anyvals.NonEmptyList
, instead.
This type has been renamed for consistency with other 'NonEmpty
' anyvals.
(Since version 3.1.0) Chain has been deprecated and will be removed in a future version of Scalactic. Please use org.scalactic.anyvals.NonEmptyList instead.
Companion object to trait Accumulation
that allows Accumulation
's members to be imported
rather than mixed in, and also contains nested traits used by implicit conversions declared in
trait Accumulations
.
Companion object to trait Accumulation
that allows Accumulation
's members to be imported
rather than mixed in, and also contains nested traits used by implicit conversions declared in
trait Accumulations
.
For more information and examples, see the Accumulating errors with Or
section
of the main documentation for class Or
.
Bool
companion object that provides factory methods to create different sub types of Bool
Bool
companion object that provides factory methods to create different sub types of Bool
Bool
is used by code generated from BooleanMacro
(which AssertionsMacro
and RequirementsMacro
uses),
it needs to be public so that the generated code can be compiled. It is expected that ScalaTest users would ever need to use Bool
directly.
Companion object for Catcher
that provides a factory method for creating Throwable
extractors.
Companion object for Catcher
that provides a factory method for creating Throwable
extractors.
Companion object for trait Equality
that provides factory methods for producing Equality
instances.
Companion object for trait Equality
that provides factory methods for producing Equality
instances.
Companion object for trait Equivalence
that provides a factory method for producing
default Equivalence
instances.
Companion object for trait Equivalence
that provides a factory method for producing
default Equivalence
instances.
Companion object for Explicitly
, which enables the Scalactic explicitly DSL to
be imported rather than mixed in, like this:
Companion object for Explicitly
, which enables the Scalactic explicitly DSL to
be imported rather than mixed in, like this:
import org.scalactic._ import Explicitly._ // Use the explicitly DSL...
Companion object for FutureSugar
enabling its members to be
imported as an alternative to mixing them in.
Companion object for FutureSugar
enabling its members to be
imported as an alternative to mixing them in.
Companion object that facilitates the importing of MapEqualityConstraints
members as
an alternative to mixing it in.
Companion object that facilitates the importing of MapEqualityConstraints
members as
an alternative to mixing it in. One use case is to import MapEqualityConstraints
members so you can use
them in the Scala interpreter.
Companion object for NormMethods
enabling its members to be imported as an alternative to mixing them in.
Companion object for NormMethods
enabling its members to be imported as an alternative to mixing them in.
Companion object for OptionSugar
enabling its members to be
imported as an alternative to mixing them in.
Companion object for OptionSugar
enabling its members to be
imported as an alternative to mixing them in.
Companion object for Prettifier
that provides a default Prettifier
implementation.
Companion object for trait PrettyMethods
enabling its members to be imported as an
alternative to mixing them in.
Companion object for trait PrettyMethods
enabling its members to be imported as an
alternative to mixing them in.
Companion object that facilitates the importing of Requirements
members as
an alternative to mixing it in.
Companion object that facilitates the importing of Requirements
members as
an alternative to mixing it in. One use case is to import Requirements
members so you can use
them in the Scala interpreter:
$scala -classpath scalatest.jar Welcome to Scala version 2.10.3.final (Java HotSpot(TM) Client VM, Java xxxxxx). Type in expressions to have them evaluated. Type :help for more information. scala> import org.scalactic.Requirements._ import org.scalactic.Requirements._ scala> val a = 1 a: Int = 1 scala> require(a == 2) java.lang.IllegalArgumentException: 1 did not equal 2 at org.scalactic.Requirements$RequirementsHelper.macroRequire(Requirements.scala:56) at .<init>(<console>:20) at .<clinit>(<console>) at .<init>(<console>:7) at .<clinit>(<console>) at $print(<console>) at sun.reflect.NativeMethodAccessorImpl.invoke...
The version number of Scalactic.
The version number of Scalactic.
the Scalactic version number.
Companion object that facilitates the importing of SeqEqualityConstraints
members as
an alternative to mixing it in.
Companion object that facilitates the importing of SeqEqualityConstraints
members as
an alternative to mixing it in. One use case is to import SeqEqualityConstraints
members so you can use
them in the Scala interpreter.
Companion object that facilitates the importing of SetEqualityConstraints
members as
an alternative to mixing it in.
Companion object that facilitates the importing of SetEqualityConstraints
members as
an alternative to mixing it in. One use case is to import SetEqualityConstraints
members so you can use
them in the Scala interpreter.
Companion object that facilitates the importing of Snapshots
members as
an alternative to mixing it in.
Companion object that facilitates the importing of Snapshots
members as
an alternative to mixing it in. One use case is to import Snapshots
members so you can use
them in the Scala interpreter:
$scala -classpath scalatest.jar Welcome to Scala version 2.10.3.final (Java HotSpot(TM) Client VM, Java xxxxxx). Type in expressions to have them evaluated. Type :help for more information. scala> import org.scalactic.Snapshots._ import org.scalatest.Snapshots._ scala> val a = 8 a: Int = 8 scala> snap(a) res0: scala.collection.immutable.Vector[org.scalactic.Snapshot] = Vector(a = 8)
Companion object to trait StringNormalizations
that provides an
alternative to mixing it in.
Companion object to trait StringNormalizations
that provides an
alternative to mixing it in.
Companion object that facilitates the importing of TimesOnInt
members as an alternative to mixing it in.
Companion object that facilitates the importing of TimesOnInt
members as an alternative to mixing it in.
One use case of this companion object is to import TimesOnInt
members so you can use them in the Scala interpreter.
Here's an example:
scala> import org.scalatest.TimesOnInt._ import org.scalatest.TimesOnInt._ scala> 3 times println("Hello again, world!") Hello again, world! Hello again, world! Hello again, world!
Companion object to trait Tolerance
that facilitates the importing of Tolerance
members as
an alternative to mixing it in.
Companion object to trait Tolerance
that facilitates the importing of Tolerance
members as
an alternative to mixing it in. One use case is to import Tolerance
members so you can use
them in the Scala interpreter:
$ scala -classpath scalactic.jar Welcome to Scala version 2.10.0 Type in expressions to have them evaluated. Type :help for more information. scala> import org.scalactic._ import org.scalactic._ scala> import Tolerance._ import Tolerance._ scala> 1.0 +- 0.1 res0: org.scalactic.TripleEqualsSupport.Spread[Double] = Spread(1.0,0.1)
Companion object for TolerantNumerics
that enables its members to be imported as an alternative to
mixing them in.
Companion object for TolerantNumerics
that enables its members to be imported as an alternative to
mixing them in.
Companion object that facilitates the importing of TraversableEqualityConstraints
members as
an alternative to mixing it in.
Companion object that facilitates the importing of TraversableEqualityConstraints
members as
an alternative to mixing it in. One use case is to import TraversableEqualityConstraints
members so you can use
them in the Scala interpreter.
Companion object to trait TripleEquals
that facilitates the importing of TripleEquals
members as
an alternative to mixing it in.
Companion object to trait TripleEquals
that facilitates the importing of TripleEquals
members as
an alternative to mixing it in. One use case is to import TripleEquals
members so you can use
them in the Scala interpreter:
$ scala -classpath scalatest.jar Welcome to Scala version 2.10.0 Type in expressions to have them evaluated. Type :help for more information. scala> import org.scalactic._ import org.scalactic._ scala> import TripleEquals._ import TripleEquals._ scala> 1 + 1 === 2 res0: Boolean = true
Companion object for TrySugar
enabling its members to be
imported as an alternative to mixing them in.
Companion object for TrySugar
enabling its members to be
imported as an alternative to mixing them in.
Companion object to trait TypeCheckedTripleEquals
that facilitates the importing of TypeCheckedTripleEquals
members as
an alternative to mixing it in.
Companion object to trait TypeCheckedTripleEquals
that facilitates the importing of TypeCheckedTripleEquals
members as
an alternative to mixing it in. One use case is to import TypeCheckedTripleEquals
members so you can use
them in the Scala interpreter:
$ scala -classpath scalatest.jar Welcome to Scala version 2.10.0 Type in expressions to have them evaluated. Type :help for more information. scala> import org.scalactic._ import org.scalactic._ scala> import TypeCheckedTripleEquals._ import TypeCheckedTripleEquals._ scala> 1 + 1 === 2 res0: Boolean = true
Returns the result of evaluating the given block f
, wrapped in a Good
, or
if an exception is thrown, the Throwable
, wrapped in a Bad
.
Returns the result of evaluating the given block f
, wrapped in a Good
, or
if an exception is thrown, the Throwable
, wrapped in a Bad
.
Here are some examples:
scala> import org.scalactic._ import org.scalactic._ scala> attempt { 2 / 1 } res0: org.scalactic.Or[Int,Throwable] = Good(2) scala> attempt { 2 / 0 } res1: org.scalactic.Or[Int,Throwable] = Bad(java.lang.ArithmeticException: / by zero)
the block to attempt to evaluate
the result of evaluating the block, wrapped in a Good
, or the
thrown exception, wrapped in a Bad
The name org.scalactic.Chain
has been deprecated and will be removed in a future version of Scalactic. Please use
its new name, org.scalatest.anyvals.NonEmptyList
, instead.
The name org.scalactic.Chain
has been deprecated and will be removed in a future version of Scalactic. Please use
its new name, org.scalatest.anyvals.NonEmptyList
, instead.
This type has been renamed for consistency with other 'NonEmpty
' anyvals.
(Since version 3.1.0) Chain has been deprecated and will be removed in a future version of Scalactic. Please use org.scalactic.anyvals.NonEmptyList instead.
The name org.scalactic.End
has been deprecated and will be removed in a future version of Scalactic. Please use
its new name, org.scalatest.anyvals.End
, instead.
The name org.scalactic.End
has been deprecated and will be removed in a future version of Scalactic. Please use
its new name, org.scalatest.anyvals.End
, instead.
This type has been renamed for consistency with other 'NonEmpty
' anyvals.
(Since version 3.1.0) End has been deprecated and will be removed in a future version of Scalactic. Please use org.scalactic.anyvals.End instead.