scalatestCoreDotty/org.scalatest/Assertions

Assertions

org.scalatest.Assertions

See theAssertions companion object

trait Assertions extends TripleEquals

Trait that contains ScalaTest's basic assertion methods.

You can use the assertions provided by this trait in any ScalaTest Suite, because Suite mixes in this trait. This trait is designed to be used independently of anything else in ScalaTest, though, so you can mix it into anything. (You can alternatively import the methods defined in this trait. For details, see the documentation for the Assertions companion object.

In any Scala program, you can write assertions by invoking assert and passing in a Boolean expression, such as:

val left = 2
val right = 1
assert(left == right)

If the passed expression is true, assert will return normally. If false, Scala's assert will complete abruptly with an AssertionError. This behavior is provided by the assert method defined in object Predef, whose members are implicitly imported into every Scala source file. This Assertions trait defines another assert method that hides the one in Predef. It behaves the same, except that if false is passed it throws TestFailedException instead of AssertionError. Why? Because unlike AssertionError, TestFailedException carries information about exactly which item in the stack trace represents the line of test code that failed, which can help users more quickly find an offending line of code in a failing test. In addition, ScalaTest's assert provides better error messages than Scala's assert.

If you pass the previous Boolean expression, left == right to assert in a ScalaTest test, a failure will be reported that, because assert is implemented as a macro, includes reporting the left and right values. For example, given the same code as above but using ScalaTest assertions:

import org.scalatest.Assertions._
val left = 2
val right = 1
assert(left == right)

The detail message in the thrown TestFailedException from this assert will be: "2 did not equal 1".

ScalaTest's assert macro works by recognizing patterns in the AST of the expression passed to assert and, for a finite set of common expressions, giving an error message that an equivalent ScalaTest matcher expression would give. Here are some examples, where a is 1, b is 2, c is 3, d is 4, xs is List(a, b, c), and num is 1.0:

assert(a == b || c >= d)
// Error message: 1 did not equal 2, and 3 was not greater than or equal to 4

assert(xs.exists(_ == 4))
// Error message: List(1, 2, 3) did not contain 4

assert("hello".startsWith("h") && "goodbye".endsWith("y"))
// Error message: "hello" started with "h", but "goodbye" did not end with "y"

assert(num.isInstanceOf[Int])
// Error message: 1.0 was not instance of scala.Int

assert(Some(2).isEmpty)
// Error message: Some(2) was not empty

For expressions that are not recognized, the macro currently prints out a string representation of the (desugared) AST and adds "was false". Here are some examples of error messages for unrecognized expressions:

assert(None.isDefined)
// Error message: scala.None.isDefined was false

assert(xs.exists(i => i > 10))
// Error message: xs.exists(((i: Int) => i.>(10))) was false

You can augment the standard error message by providing a String as a second argument to assert, like this:

val attempted = 2
assert(attempted == 1, "Execution was attempted " + attempted + " times instead of 1 time")

Using this form of assert, the failure report will be more specific to your problem domain, thereby helping you debug the problem. This Assertions trait also mixes in the TripleEquals, which gives you a === operator that allows you to customize Equality, perform equality checks with numeric Tolerance, and enforce type constraints at compile time with sibling traits TypeCheckedTripleEquals and ConversionCheckedTripleEquals.

== Expected results ==

Although the assert macro provides a natural, readable extension to Scala's assert mechanism that provides good error messages, as the operands become lengthy, the code becomes less readable. In addition, the error messages generated for == and === comparisons don't distinguish between actual and expected values. The operands are just called left and right, because if one were named expected and the other actual, it would be difficult for people to remember which was which. To help with these limitations of assertions, Suite includes a method called assertResult that can be used as an alternative to assert. To use assertResult, you place the expected value in parentheses after assertResult, followed by curly braces containing code that should result in the expected value. For example:

val a = 5
val b = 2
assertResult(2) {
 a - b
}

In this case, the expected value is 2, and the code being tested is a - b. This assertion will fail, and the detail message in the TestFailedException will read, "Expected 2, but got 3."

== Forcing failures ==

If you just need the test to fail, you can write:

fail()

Or, if you want the test to fail with a message, write:

fail("I've got a bad feeling about this")

== Achieving success ==

In async style tests, you must end your test body with either Future[Assertion] or Assertion. ScalaTest's assertions (including matcher expressions) have result type Assertion, so ending with an assertion will satisfy the compiler. If a test body or function body passed to Future.map does not end with type Assertion, however, you can fix the type error by placing succeed at the end of the test or function body:

succeed // Has type Assertion

== Expected exceptions ==

Sometimes you need to test whether a method throws an expected exception under certain circumstances, such as when invalid arguments are passed to the method. You can do this in the JUnit 3 style, like this:

val s = "hi"
try {
 s.charAt(-1)
 fail()
}
catch {
 case _: IndexOutOfBoundsException => // Expected, so continue
}

If charAt throws IndexOutOfBoundsException as expected, control will transfer to the catch case, which does nothing. If, however, charAt fails to throw an exception, the next statement, fail(), will be run. The fail method always completes abruptly with a TestFailedException, thereby signaling a failed test.

To make this common use case easier to express and read, ScalaTest provides two methods: assertThrows and intercept. Here's how you use assertThrows:

val s = "hi"
assertThrows[IndexOutOfBoundsException] { // Result type: Assertion
 s.charAt(-1)
}

This code behaves much like the previous example. If charAt throws an instance of IndexOutOfBoundsException, assertThrows will return Succeeded. But if charAt completes normally, or throws a different exception, assertThrows will complete abruptly with a TestFailedException.

The intercept method behaves the same as assertThrows, except that instead of returning Succeeded, intercept returns the caught exception so that you can inspect it further if you wish. For example, you may need to ensure that data contained inside the exception have expected values. Here's an example:

val s = "hi"
val caught =
 intercept[IndexOutOfBoundsException] { // Result type: IndexOutOfBoundsException
   s.charAt(-1)
 }
assert(caught.getMessage.indexOf("-1") != -1)

== Checking that a snippet of code does or does not compile ==

Often when creating libraries you may wish to ensure that certain arrangements of code that represent potential “user errors” do not compile, so that your library is more error resistant. ScalaTest's Assertions trait includes the following syntax for that purpose:

assertDoesNotCompile("val a: String = 1")

If you want to ensure that a snippet of code does not compile because of a type error (as opposed to a syntax error), use:

assertTypeError("val a: String = 1")

Note that the assertTypeError call will only succeed if the given snippet of code does not compile because of a type error. A syntax error will still result on a thrown TestFailedException.

If you want to state that a snippet of code does compile, you can make that more obvious with:

assertCompiles("val a: Int = 1")

Although the previous three constructs are implemented with macros that determine at compile time whether the snippet of code represented by the string does or does not compile, errors are reported as test failures at runtime.

== Assumptions ==

Trait Assertions also provides methods that allow you to cancel a test. You would cancel a test if a resource required by the test was unavailable. For example, if a test requires an external database to be online, and it isn't, the test could be canceled to indicate it was unable to run because of the missing database. Such a test assumes a database is available, and you can use the assume method to indicate this at the beginning of the test, like this:

assume(database.isAvailable)

For each overloaded assert method, trait Assertions provides an overloaded assume method with an identical signature and behavior, except the assume methods throw TestCanceledException whereas the assert methods throw TestFailedException. As with assert, assume hides a Scala method in Predef that performs a similar function, but throws AssertionError. And just as you can with assert, you will get an error message extracted by a macro from the AST passed to assume, and can optionally provide a clue string to augment this error message. Here are some examples:

assume(database.isAvailable, "The database was down again")
assume(database.getAllUsers.count === 9)

== Forcing cancelations ==

For each overloaded fail method, there's a corresponding cancel method with an identical signature and behavior, except the cancel methods throw TestCanceledException whereas the fail methods throw TestFailedException. Thus if you just need to cancel a test, you can write:

cancel()

If you want to cancel the test with a message, just place the message in the parentheses:

cancel("Can't run the test because no internet connection was found")

== Getting a clue ==

If you want more information that is provided by default by the methods if this trait, you can supply a "clue" string in one of several ways. The extra information (or "clues") you provide will be included in the detail message of the thrown exception. Both assert and assertResult provide a way for a clue to be included directly, intercept does not. Here's an example of clues provided directly in assert:

assert(1 + 1 === 3, "this is a clue")

and in assertResult:

assertResult(3, "this is a clue") { 1 + 1 }

The exceptions thrown by the previous two statements will include the clue string, "this is a clue", in the exception's detail message. To get the same clue in the detail message of an exception thrown by a failed intercept call requires using withClue:

withClue("this is a clue") {
 intercept[IndexOutOfBoundsException] {
   "hi".charAt(-1)
 }
}

The withClue method will only prepend the clue string to the detail message of exception types that mix in the ModifiableMessage trait. See the documentation for ModifiableMessage for more information. If you wish to place a clue string after a block of code, see the documentation for AppendedClues.

Note: ScalaTest's assertTypeError construct is in part inspired by the illTyped macro of shapeless.

Attributes

Companion: object
Graph
Supertypes: trait TripleEquals

trait TripleEqualsSupport

class Object

trait Matchable

class Any
Known subtypes: object Assertions.type

trait NonImplicitAssertions

object NonImplicitAssertions.type

trait Suite

trait AsyncTestSuite

trait FixtureAsyncTestSuite

class ConfigMapWrapperSuite

trait FixtureSuite

trait FixtureTestSuite

class Sequential

class Stepwise

class Suites

trait TestSuite
Show all

Members list

Type members

Classlikes

Attributes

Supertypes: class Object

trait Matchable

class Any
Self type: UseDefaultAssertions.type

Inherited classlikes

Class used via an implicit conversion to enable two objects to be compared with === and !== with a Boolean result and an enforced type constraint between two object types. For example:

assert(a === b)
assert(c !== d)

You can also check numeric values against another with a tolerance. Here are some examples:

assert(a === (2.0 +- 0.1))
assert(c !== (2.0 +- 0.1))

Value parameters

leftSide: An object to convert to Equalizer, which represents the value on the left side of a === or !== invocation.

Attributes

Inherited from:: TripleEqualsSupport
Supertypes: class Object

trait Matchable

class Any

Class used via an implicit conversion to enable any two objects to be compared with === and !== with a Boolean result and no enforced type constraint between two object types. For example:

assert(a === b)
assert(c !== d)

You can also check numeric values against another with a tolerance. Here are some examples:

assert(a === (2.0 +- 0.1))
assert(c !== (2.0 +- 0.1))

Value parameters

leftSide: An object to convert to Equalizer, which represents the value on the left side of a === or !== invocation.

Attributes

Inherited from:: TripleEqualsSupport
Supertypes: class Object

trait Matchable

class Any

Value members

Concrete methods

Assert that a boolean condition is true. If the condition is true, this method returns normally. Else, it throws TestFailedException.

This method is implemented in terms of a Scala macro that will generate a more helpful error message for expressions of this form:

assert(a == b)
assert(a != b)
assert(a === b)
assert(a !== b)
assert(a > b)
assert(a >= b)
assert(a < b)
assert(a <= b)
assert(a startsWith "prefix")
assert(a endsWith "postfix")
assert(a contains "something")
assert(a eq b)
assert(a ne b)
assert(a > 0 && b > 5)
assert(a > 0 || b > 5)
assert(a.isEmpty)
assert(!a.isEmpty)
assert(a.isInstanceOf[String])
assert(a.length == 8)
assert(a.size == 8)
assert(a.exists(_ == 8))

At this time, any other form of expression will get a TestFailedException with message saying the given expression was false. In the future, we will enhance this macro to give helpful error messages in more situations. In ScalaTest 2.0, however, this behavior was sufficient to allow the === that returns Boolean to be the default in tests. This makes === consistent between tests and production code.

Value parameters

condition: the boolean condition to assert

Attributes

Throws: org.scalatest.exceptions.TestFailedException
if the condition is false.

Assert that a boolean condition, described in String message, is true. If the condition is true, this method returns normally. Else, it throws TestFailedException with a helpful error message appended with the String obtained by invoking toString on the specified clue as the exception's detail message.

This method is implemented in terms of a Scala macro that will generate a more helpful error message for expressions of this form:

assert(a == b, "a good clue")
assert(a != b, "a good clue")
assert(a === b, "a good clue")
assert(a !== b, "a good clue")
assert(a > b, "a good clue")
assert(a >= b, "a good clue")
assert(a < b, "a good clue")
assert(a <= b, "a good clue")
assert(a startsWith "prefix", "a good clue")
assert(a endsWith "postfix", "a good clue")
assert(a contains "something", "a good clue")
assert(a eq b, "a good clue")
assert(a ne b, "a good clue")
assert(a > 0 && b > 5, "a good clue")
assert(a > 0 || b > 5, "a good clue")
assert(a.isEmpty, "a good clue")
assert(!a.isEmpty, "a good clue")
assert(a.isInstanceOf[String], "a good clue")
assert(a.length == 8, "a good clue")
assert(a.size == 8, "a good clue")
assert(a.exists(_ == 8), "a good clue")

At this time, any other form of expression will just get a TestFailedException with message saying the given expression was false. In the future, we will enhance this macro to give helpful error messages in more situations. In ScalaTest 2.0, however, this behavior was sufficient to allow the === that returns Boolean to be the default in tests. This makes === consistent between tests and production code.

Value parameters

clue: An objects whose toString method returns a message to include in a failure report.
condition: the boolean condition to assert

Attributes

Throws: org.scalactic.exceptions.NullArgumentException
if message is null.

org.scalatest.exceptions.TestFailedException
if the condition is false.

Asserts that a given string snippet of code passes both the Scala parser and type checker.

You can use this to make sure a snippet of code compiles:

assertCompiles("val a: Int = 1")

Although assertCompiles is implemented with a macro that determines at compile time whether the snippet of code represented by the passed string compiles, errors (i.e., snippets of code that do not compile) are reported as test failures at runtime.

Value parameters

code: the snippet of code that should compile

Attributes

Asserts that a given string snippet of code does not pass either the Scala parser or type checker.

assertDoesNotCompile("val a: String = \"a string")

Although assertDoesNotCompile is implemented with a macro that determines at compile time whether the snippet of code represented by the passed string doesn't compile, errors (i.e., snippets of code that do compile) are reported as test failures at runtime.

Note that the difference between assertTypeError and assertDoesNotCompile is that assertDoesNotCompile will succeed if the given code does not compile for any reason, whereas assertTypeError will only succeed if the given code does not compile because of a type error. If the given code does not compile because of a syntax error, for example, assertDoesNotCompile will return normally but assertTypeError will throw a TestFailedException.

Value parameters

code: the snippet of code that should not type check

Attributes

Assert that the value passed as expected equals the value passed as actual. If the actual equals the expected (as determined by ==), assertResult returns normally. Else, if actual is not equal to expected, assertResult throws a TestFailedException whose detail message includes the expected and actual values, as well as the String obtained by invoking toString on the passed clue.

Value parameters

actual: the actual value, which should equal the passed expected value
clue: An object whose toString method returns a message to include in a failure report.
expected: the expected value

Attributes

Throws: org.scalatest.exceptions.TestFailedException
if the passed actual value does not equal the passed expected value.

Assert that the value passed as expected equals the value passed as actual. If the actual value equals the expected value (as determined by ==), assertResult returns normally. Else, assertResult throws a TestFailedException whose detail message includes the expected and actual values.

Value parameters

actual: the actual value, which should equal the passed expected value
expected: the expected value

Attributes

Throws: org.scalatest.exceptions.TestFailedException
if the passed actual value does not equal the passed expected value.

Ensure that an expected exception is thrown by the passed function value. The thrown exception must be an instance of the type specified by the type parameter of this method. This method invokes the passed function. If the function throws an exception that's an instance of the specified type, this method returns Succeeded. Else, whether the passed function returns normally or completes abruptly with a different exception, this method throws TestFailedException.

Note that the type specified as this method's type parameter may represent any subtype of AnyRef, not just Throwable or one of its subclasses. In Scala, exceptions can be caught based on traits they implement, so it may at times make sense to specify a trait that the intercepted exception's class must mix in. If a class instance is passed for a type that could not possibly be used to catch an exception (such as String, for example), this method will complete abruptly with a TestFailedException.

Also note that the difference between this method and intercept is that this method does not return the expected exception, so it does not let you perform further assertions on that exception. Instead, this method returns Succeeded, which means it can serve as the last statement in an async- or safe-style suite. It also indicates to the reader of the code that nothing further is expected about the thrown exception other than its type. The recommended usage is to use assertThrows by default, intercept only when you need to inspect the caught exception further.

Value parameters

classTag: an implicit ClassTag representing the type of the specified type parameter.
f: the function value that should throw the expected exception

Attributes

Returns: the Succeeded singleton, if an exception of the expected type is thrown
Throws: org.scalatest.exceptions.TestFailedException
if the passed function does not complete abruptly with an exception that's an instance of the specified type.

Asserts that a given string snippet of code does not pass the Scala type checker, failing if the given snippet does not pass the Scala parser.

assertTypeError("val a: String = 1")

Although assertTypeError is implemented with a macro that determines at compile time whether the snippet of code represented by the passed string type checks, errors (i.e., snippets of code that do type check) are reported as test failures at runtime.

Value parameters

code: the snippet of code that should not type check

Attributes

Assume that a boolean condition is true. If the condition is true, this method returns normally. Else, it throws TestCanceledException.

This method is implemented in terms of a Scala macro that will generate a more helpful error message for expressions of this form:

assume(a == b)
assume(a != b)
assume(a === b)
assume(a !== b)
assume(a > b)
assume(a >= b)
assume(a < b)
assume(a <= b)
assume(a startsWith "prefix")
assume(a endsWith "postfix")
assume(a contains "something")
assume(a eq b)
assume(a ne b)
assume(a > 0 && b > 5)
assume(a > 0 || b > 5)
assume(a.isEmpty)
assume(!a.isEmpty)
assume(a.isInstanceOf[String])
assume(a.length == 8)
assume(a.size == 8)
assume(a.exists(_ == 8))

At this time, any other form of expression will just get a TestCanceledException with message saying the given expression was false. In the future, we will enhance this macro to give helpful error messages in more situations. In ScalaTest 2.0, however, this behavior was sufficient to allow the === that returns Boolean to be the default in tests. This makes === consistent between tests and production code.

Value parameters

condition: the boolean condition to assume

Attributes

Throws: org.scalatest.exceptions.TestCanceledException
if the condition is false.

Assume that a boolean condition, described in String message, is true. If the condition is true, this method returns normally. Else, it throws TestCanceledException with a helpful error message appended with String obtained by invoking toString on the specified clue as the exception's detail message.

This method is implemented in terms of a Scala macro that will generate a more helpful error message for expressions of this form:

assume(a == b, "a good clue")
assume(a != b, "a good clue")
assume(a === b, "a good clue")
assume(a !== b, "a good clue")
assume(a > b, "a good clue")
assume(a >= b, "a good clue")
assume(a < b, "a good clue")
assume(a <= b, "a good clue")
assume(a startsWith "prefix", "a good clue")
assume(a endsWith "postfix", "a good clue")
assume(a contains "something", "a good clue")
assume(a eq b, "a good clue")
assume(a ne b, "a good clue")
assume(a > 0 && b > 5, "a good clue")
assume(a > 0 || b > 5, "a good clue")
assume(a.isEmpty, "a good clue")
assume(!a.isEmpty, "a good clue")
assume(a.isInstanceOf[String], "a good clue")
assume(a.length == 8, "a good clue")
assume(a.size == 8, "a good clue")
assume(a.exists(_ == 8), "a good clue")

Value parameters

clue: An objects whose toString method returns a message to include in a failure report.
condition: the boolean condition to assume

Attributes

Throws: org.scalactic.exceptions.NullArgumentException
if message is null.

org.scalatest.exceptions.TestCanceledException
if the condition is false.

Throws TestCanceledException to indicate a test was canceled.

Attributes

Throws TestCanceledException, with the passed String message as the exception's detail message, to indicate a test was canceled.

Value parameters

message: A message describing the cancellation.

Attributes

Throws: org.scalactic.exceptions.NullArgumentException
if message is null

Throws TestCanceledException, with the passed String message as the exception's detail message and Throwable cause, to indicate a test failed.

Value parameters

cause: A Throwable that indicates the cause of the failure.
message: A message describing the failure.

Attributes

Throws: org.scalactic.exceptions.NullArgumentException
if message or cause is null

Throws TestCanceledException, with the passed Throwable cause, to indicate a test failed. The getMessage method of the thrown TestCanceledException will return cause.toString.

Value parameters

cause: a Throwable that indicates the cause of the cancellation.

Attributes

Throws: org.scalactic.exceptions.NullArgumentException
if cause is null

Throws TestFailedException to indicate a test failed.

Attributes

Throws TestFailedException, with the passed String message as the exception's detail message, to indicate a test failed.

Value parameters

message: A message describing the failure.

Attributes

Throws: org.scalactic.exceptions.NullArgumentException
if message is null

Throws TestFailedException, with the passed String message as the exception's detail message and Throwable cause, to indicate a test failed.

Value parameters

cause: A Throwable that indicates the cause of the failure.
message: A message describing the failure.

Attributes

Throws: org.scalactic.exceptions.NullArgumentException
if message or cause is null

Throws TestFailedException, with the passed Throwable cause, to indicate a test failed. The getMessage method of the thrown TestFailedException will return cause.toString.

Value parameters

cause: a Throwable that indicates the cause of the failure.

Attributes

Throws: org.scalactic.exceptions.NullArgumentException
if cause is null

Intercept and return an exception that's expected to be thrown by the passed function value. The thrown exception must be an instance of the type specified by the type parameter of this method. This method invokes the passed function. If the function throws an exception that's an instance of the specified type, this method returns that exception. Else, whether the passed function returns normally or completes abruptly with a different exception, this method throws TestFailedException.

Also note that the difference between this method and assertThrows is that this method returns the expected exception, so it lets you perform further assertions on that exception. By contrast, the assertThrows method returns Succeeded, which means it can serve as the last statement in an async- or safe-style suite. assertThrows also indicates to the reader of the code that nothing further is expected about the thrown exception other than its type. The recommended usage is to use assertThrows by default, intercept only when you need to inspect the caught exception further.

Value parameters

classTag: an implicit ClassTag representing the type of the specified type parameter.
f: the function value that should throw the expected exception

Attributes

Returns: the intercepted exception, if it is of the expected type
Throws: org.scalatest.exceptions.TestFailedException
if the passed function does not complete abruptly with an exception that's an instance of the specified type.

Throws TestPendingException to indicate a test is pending.

A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, the before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later.

To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality it is intended to test, has not yet been implemented.

Note: This method always completes abruptly with a TestPendingException. Thus it always has a side effect. Methods with side effects are usually invoked with parentheses, as in pending(). This method is defined as a parameterless method, in flagrant contradiction to recommended Scala style, because it forms a kind of DSL for pending tests. It enables tests in suites such as FunSuite or FunSpec to be denoted by placing "(pending)" after the test name, as in:

test("that style rules are not laws") (pending)

Readers of the code see "pending" in parentheses, which looks like a little note attached to the test name to indicate it is pending. Whereas "(pending()) looks more like a method call, "(pending)" lets readers stay at a higher level, forgetting how it is implemented and just focusing on the intent of the programmer who wrote the code.

Attributes

Execute the passed block of code, and if it completes abruptly, throw TestPendingException, else throw TestFailedException.

This method can be used to temporarily change a failing test into a pending test in such a way that it will automatically turn back into a failing test once the problem originally causing the test to fail has been fixed. At that point, you need only remove the pendingUntilFixed call. In other words, a pendingUntilFixed surrounding a block of code that isn't broken is treated as a test failure. The motivation for this behavior is to encourage people to remove pendingUntilFixed calls when there are no longer needed.

This method facilitates a style of testing in which tests are written before the code they test. Sometimes you may encounter a test failure that requires more functionality than you want to tackle without writing more tests. In this case you can mark the bit of test code causing the failure with pendingUntilFixed. You can then write more tests and functionality that eventually will get your production code to a point where the original test won't fail anymore. At this point the code block marked with pendingUntilFixed will no longer throw an exception (because the problem has been fixed). This will in turn cause pendingUntilFixed to throw TestFailedException with a detail message explaining you need to go back and remove the pendingUntilFixed call as the problem orginally causing your test code to fail has been fixed.

Value parameters

f: a block of code, which if it completes abruptly, should trigger a TestPendingException

Attributes

Throws: org.scalatest.exceptions.TestPendingException
if the passed block of code completes abruptly with an Exception or AssertionError

Executes the block of code passed as the second parameter, and, if it completes abruptly with a ModifiableMessage exception, prepends the "clue" string passed as the first parameter to the beginning of the detail message of that thrown exception, then rethrows it. If clue does not end in a white space character, one space will be added between it and the existing detail message (unless the detail message is not defined).

This method allows you to add more information about what went wrong that will be reported when a test fails. Here's an example:

withClue("(Employee's name was: " + employee.name + ")") {
 intercept[IllegalArgumentException] {
   employee.getTask(-1)
 }
}

If an invocation of intercept completed abruptly with an exception, the resulting message would be something like:

(Employee's name was Bob Jones) Expected IllegalArgumentException to be thrown, but no exception was thrown

Attributes

Throws: org.scalactic.exceptions.NullArgumentException
if the passed clue is null

Deprecated methods

Trap and return any thrown exception that would normally cause a ScalaTest test to fail, or create and return a new RuntimeException indicating no exception is thrown.

This method is intended to be used in the Scala interpreter to eliminate large stack traces when trying out ScalaTest assertions and matcher expressions. It is not intended to be used in regular test code. If you want to ensure that a bit of code throws an expected exception, use intercept, not trap. Here's an example interpreter session without trap:

scala> import org.scalatest._
import org.scalatest._

scala> import Matchers._
import Matchers._

scala> val x = 12
a: Int = 12

scala> x shouldEqual 13
org.scalatest.exceptions.TestFailedException: 12 did not equal 13
  at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:449)
  at org.scalatest.Assertions$.newAssertionFailedException(Assertions.scala:1203)
  at org.scalatest.Assertions$AssertionsHelper.macroAssertTrue(Assertions.scala:417)
  at .<init>(<console>:15)
  at .<clinit>(<console>)
  at .<init>(<console>:7)
  at .<clinit>(<console>)
  at $print(<console>)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:597)
  at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:731)
  at scala.tools.nsc.interpreter.IMain$Request.loadAndRun(IMain.scala:980)
  at scala.tools.nsc.interpreter.IMain.loadAndRunReq$1(IMain.scala:570)
  at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:601)
  at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:565)
  at scala.tools.nsc.interpreter.ILoop.reallyInterpret$1(ILoop.scala:745)
  at scala.tools.nsc.interpreter.ILoop.interpretStartingWith(ILoop.scala:790)
  at scala.tools.nsc.interpreter.ILoop.command(ILoop.scala:702)
  at scala.tools.nsc.interpreter.ILoop.processLine$1(ILoop.scala:566)
  at scala.tools.nsc.interpreter.ILoop.innerLoop$1(ILoop.scala:573)
  at scala.tools.nsc.interpreter.ILoop.loop(ILoop.scala:576)
  at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply$mcZ$sp(ILoop.scala:867)
  at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:822)
  at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:822)
  at scala.tools.nsc.util.ScalaClassLoader$.savingContextLoader(ScalaClassLoader.scala:135)
  at scala.tools.nsc.interpreter.ILoop.process(ILoop.scala:822)
  at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:83)
  at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:96)
  at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:105)
  at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)

That's a pretty tall stack trace. Here's what it looks like when you use trap:

scala> trap { x shouldEqual 13 }
res1: Throwable = org.scalatest.exceptions.TestFailedException: 12 did not equal 13

Much less clutter. Bear in mind, however, that if no exception is thrown by the passed block of code, the trap method will create a new NormalResult (a subclass of Throwable made for this purpose only) and return that. If the result was the Unit value, it will simply say that no exception was thrown:

scala> trap { x shouldEqual 12 }
res2: Throwable = No exception was thrown.

If the passed block of code results in a value other than Unit, the NormalResult's toString will print the value:

scala> trap { "Dude!" }
res3: Throwable = No exception was thrown. Instead, result was: "Dude!"

Although you can access the result value from the NormalResult, its type is Any and therefore not very convenient to use. It is not intended that trap be used in test code. The sole intended use case for trap is decluttering Scala interpreter sessions by eliminating stack traces when executing assertion and matcher expressions.

Attributes

Deprecated: true

Inherited methods

Returns a TripleEqualsInvocationOnSpread[T], given an Spread[T], to facilitate the “<left> should !== (<pivot> +- <tolerance>)” syntax of Matchers.

Value parameters

right: the Spread[T] against which to compare the left-hand value

Attributes

Returns: a TripleEqualsInvocationOnSpread wrapping the passed Spread[T] value, with expectingEqual set to false.
Inherited from:: TripleEqualsSupport

Returns a TripleEqualsInvocation[Null], given a null reference, to facilitate the “<left> should !== null” syntax of Matchers.

Value parameters

right: a null reference

Attributes

Returns: a TripleEqualsInvocation wrapping the passed null value, with expectingEqual set to false.
Inherited from:: TripleEqualsSupport

Returns a TripleEqualsInvocation[T], given an object of type T, to facilitate the “<left> should !== <right>” syntax of Matchers.

Value parameters

right: the right-hand side value for an equality assertion

Attributes

Returns: a TripleEqualsInvocation wrapping the passed right value, with expectingEqual set to false.
Inherited from:: TripleEqualsSupport

Returns a TripleEqualsInvocationOnSpread[T], given an Spread[T], to facilitate the “<left> should === (<pivot> +- <tolerance>)” syntax of Matchers.

Value parameters

right: the Spread[T] against which to compare the left-hand value

Attributes

Returns: a TripleEqualsInvocationOnSpread wrapping the passed Spread[T] value, with expectingEqual set to true.
Inherited from:: TripleEqualsSupport

Returns a TripleEqualsInvocation[Null], given a null reference, to facilitate the “<left> should === null” syntax of Matchers.

Value parameters

right: a null reference

Attributes

Returns: a TripleEqualsInvocation wrapping the passed null value, with expectingEqual set to true.
Inherited from:: TripleEqualsSupport

Returns a TripleEqualsInvocation[T], given an object of type T, to facilitate the “<left> should === <right>” syntax of Matchers.

Value parameters

right: the right-hand side value for an equality assertion

Attributes

Returns: a TripleEqualsInvocation wrapping the passed right value, with expectingEqual set to true.
Inherited from:: TripleEqualsSupport

Provides a A CanEqual B for any two types A and B, enforcing the type constraint that A must be a subtype of B, given an explicit Equivalence[B].

The returned Constraint's areEqual method uses the implicitly passed Equivalence[B]'s areEquivalent method to determine equality.

This method is overridden and made implicit by subtraits LowPriorityTypeCheckedConstraint (extended by TypeCheckedTripleEquals), and overriden as non-implicit by the other subtraits in this package.

Value parameters

equivalenceOfB: an Equivalence[B] type class to which the Constraint.areEqual method will delegate to determine equality.
ev: evidence that A is a subype of B

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].
Definition Classes: TripleEquals -> TripleEqualsSupport
Inherited from:: TripleEquals

Provides an A CanEqual B instance for any two types A and B, enforcing the type constraint that B must be a subtype of A, given an explicit Equivalence[A].

This method is used to enable the Explicitly DSL for TypeCheckedTripleEquals by requiring an explicit Equivalance[B], but taking an implicit function that provides evidence that A is a subtype of B. For example, under TypeCheckedTripleEquals, this method (as an implicit method), would be used to compile this statement:

def closeEnoughTo1(num: Double): Boolean =
 (num === 1.0)(decided by forgivingEquality)

The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.

This method is overridden and made implicit by subtraits TypeCheckedTripleEquals) and overriden as non-implicit by the other subtraits in this package.

Value parameters

equalityOfA: an Equivalence[A] type class to which the Constraint.areEqual method will delegate to determine equality.
ev: evidence that B is a subype of A

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].
Definition Classes: TripleEquals -> TripleEqualsSupport
Inherited from:: TripleEquals

Converts to an CheckingEqualizer that provides === and !== operators that result in Boolean and enforce a type constraint.

This method is overridden and made implicit by subtrait TypeCheckedTripleEquals, and overriden as non-implicit by the other subtraits in this package.

Value parameters

left: the object whose type to convert to CheckingEqualizer.

Attributes

Throws: NullPointerException
if left is null.
Definition Classes: TripleEquals -> TripleEqualsSupport
Inherited from:: TripleEquals

Returns an Equality[A] for any type A that determines equality by first calling .deep on any Array (on either the left or right side), then comparing the resulting objects with ==.

Attributes

Returns: a default Equality for type A
Inherited from:: TripleEqualsSupport

Provides an A CanEqual B for any two types A and B, enforcing the type constraint that A must be a subtype of B, given an implicit Equivalence[B].

The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.

Value parameters

equivalenceOfB: an Equivalence[B] type class to which the Constraint.areEqual method will delegate to determine equality.
ev: evidence that A is a subype of B

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].
Definition Classes: TripleEquals -> TripleEqualsSupport
Inherited from:: TripleEquals

Provides an A CanEqual B instance for any two types A and B, enforcing the type constraint that B must be a subtype of A, given an implicit Equivalence[A].

The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.

This method is overridden and made implicit by subtraits TypeCheckedTripleEquals) and overriden as non-implicit by the other subtraits in this package.

Value parameters

equalityOfA: an Equivalence[A] type class to which the Constraint.areEqual method will delegate to determine equality.
ev: evidence that B is a subype of A

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].
Definition Classes: TripleEquals -> TripleEqualsSupport
Inherited from:: TripleEquals

Deprecated and Inherited methods

The conversionCheckedConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

Provides an A CanEqual B instance for any two types A and B, enforcing the type constraint that B is implicitly convertible to A, given an implicit Equivalence[A].

The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.

This method is overridden and made implicit by subtraits ConversionCheckedTripleEquals) and overriden as non-implicit by the other subtraits in this package.

Value parameters

cnv: an implicit conversion from B to A
equivalenceOfA: an Equivalence[A] type class to which the Constraint.areEqual method will delegate to determine equality.

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].
Deprecated: true
Definition Classes: TripleEquals -> TripleEqualsSupport
Inherited from:: TripleEquals

The convertEquivalenceToAToBConversionConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

Provides an A CanEqual B instance for any two types A and B, enforcing the type constraint that A is implicitly convertible to B, given an explicit Equivalence[B].

This method is used to enable the Explicitly DSL for ConversionCheckedTripleEquals by requiring an explicit Equivalance[B], but taking an implicit function that converts from A to B.

The returned Constraint's areEqual method uses the implicitly passed Equivalence[B]'s areEquivalent method to determine equality.

This method is overridden and made implicit by subtraits LowPriorityConversionCheckedConstraint (extended by ConversionCheckedTripleEquals), and overriden as non-implicit by the other subtraits in this package.

Value parameters

cnv: an implicit conversion from A to B
equalityOfB: an Equivalence[B] type class to which the Constraint.areEqual method will delegate to determine equality.

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].
Deprecated: true
Definition Classes: TripleEquals -> TripleEqualsSupport
Inherited from:: TripleEquals

The convertEquivalenceToBToAConversionConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

Provides an A CanEqual B instance for any two types A and B, enforcing the type constraint that B is implicitly convertible to A, given an explicit Equivalence[A].

This method is used to enable the Explicitly DSL for ConversionCheckedTripleEquals by requiring an explicit Equivalance[A], but taking an implicit function that converts from B to A. For example, under ConversionCheckedTripleEquals, this method (as an implicit method), would be used to compile this statement:

def closeEnoughTo1(num: Double): Boolean =
 (num === 1.0)(decided by forgivingEquality)

The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.

This method is overridden and made implicit by subtraits ConversionCheckedTripleEquals) and overriden as non-implicit by the other subtraits in this package.

Value parameters

cnv: an implicit conversion from B to A
equivalenceOfA: an Equivalence[A] type class to which the Constraint.areEqual method will delegate to determine equality.

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].
Deprecated: true
Definition Classes: TripleEquals -> TripleEqualsSupport
Inherited from:: TripleEquals

The lowPriorityConversionCheckedConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

Provides an A CanEqual B instance for any two types A and B, enforcing the type constraint that A is implicitly convertible to B, given an implicit Equivalence[B].

The returned Constraint's areEqual method uses the implicitly passed Equivalence[B]'s areEquivalent method to determine equality.

Value parameters

cnv: an implicit conversion from A to B
equalityOfB: an Equivalence[B] type class to which the Constraint.areEqual method will delegate to determine equality.

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].
Deprecated: true
Definition Classes: TripleEquals -> TripleEqualsSupport
Inherited from:: TripleEquals

Concrete fields

The Succeeded singleton.

You can use succeed to solve a type error when an async test does not end in either Future[Assertion] or Assertion. Because Assertion is a type alias for Succeeded.type, putting succeed at the end of a test body (or at the end of a function being used to map the final future of a test body) will solve the type error.

Attributes

Extensions

extension (x: String)

Implicits

Inherited implicits

Converts to an Equalizer that provides === and !== operators that result in Boolean and enforce no type constraint.

This method is overridden and made implicit by subtrait TripleEquals and overriden as non-implicit by the other subtraits in this package.

Value parameters

left: the object whose type to convert to Equalizer.

Attributes

Throws: NullPointerException
if left is null.
Definition Classes: TripleEquals -> TripleEqualsSupport
Inherited from:: TripleEquals

Provides an A CanEqual B instance for any two types A and B, with no type constraint enforced, given an implicit Equality[A].

The returned Constraint's areEqual method uses the implicitly passed Equality[A]'s areEqual method to determine equality.

This method is overridden and made implicit by subtraits TripleEquals and overriden as non-implicit by the other subtraits in this package.

Value parameters

equalityOfA: an Equality[A] type class to which the Constraint.areEqual method will delegate to determine equality.

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEqual method of the passed Equality[A].
Definition Classes: TripleEquals -> TripleEqualsSupport
Inherited from:: TripleEquals

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