Package org.assertj.core.api

Class AutoCloseableSoftAssertions

  • All Implemented Interfaces:
    AutoCloseable, InstanceOfAssertFactories
    public class AutoCloseableSoftAssertions
extends SoftAssertions
implements AutoCloseable
    A version of SoftAssertions that uses try-with-resources statement to automatically call SoftAssertions.assertAll() so that you don't forget to.

    Suppose we have a test case and in it we'd like to make numerous assertions. In this case, we're hosting a dinner party and we want to ensure not only that all our guests survive but also that nothing in the mansion has been unduly disturbed: 

     @Test
 public void host_dinner_party_where_nobody_dies() {
   Mansion mansion = new Mansion();
   mansion.hostPotentiallyMurderousDinnerParty();
   assertThat(mansion.guests()).as("Living Guests").isEqualTo(7);
   assertThat(mansion.kitchen()).as("Kitchen").isEqualTo("clean");
   assertThat(mansion.library()).as("Library").isEqualTo("clean");
   assertThat(mansion.revolverAmmo()).as("Revolver Ammo").isEqualTo(6);
   assertThat(mansion.candlestick()).as("Candlestick").isEqualTo("pristine");
   assertThat(mansion.colonel()).as("Colonel").isEqualTo("well kempt");
   assertThat(mansion.professor()).as("Professor").isEqualTo("well kempt");
 }

    After running the test, JUnit provides us with the following exception message: 

     org.junit.ComparisonFailure: [Living Guests] expected:<[7]> but was:<[6]>

    Oh no! A guest has been murdered! But where, how, and by whom?

    Unfortunately frameworks like JUnit halt the test upon the first failed assertion. Therefore, to collect more evidence, we'll have to rerun the test (perhaps after attaching a debugger or modifying the test to skip past the first assertion). Given that hosting dinner parties takes a long time, this seems rather inefficient.

    Instead let's change the test so that at its completion we get the result of all assertions at once. We can do that by using a SoftAssertions instance instead of the static methods on Assertions as follows: 

     @Test
 public void host_dinner_party_where_nobody_dies() {
   Mansion mansion = new Mansion();
   mansion.hostPotentiallyMurderousDinnerParty();
   try (AutoCloseableSoftAssertions softly = new AutoCloseableSoftAssertions()) {
        softly.assertThat(mansion.guests()).as("Living Guests").isEqualTo(7);
        softly.assertThat(mansion.kitchen()).as("Kitchen").isEqualTo("clean");
        softly.assertThat(mansion.library()).as("Library").isEqualTo("clean");
        softly.assertThat(mansion.revolverAmmo()).as("Revolver Ammo").isEqualTo(6);
        softly.assertThat(mansion.candlestick()).as("Candlestick").isEqualTo("pristine");
        softly.assertThat(mansion.colonel()).as("Colonel").isEqualTo("well kempt");
        softly.assertThat(mansion.professor()).as("Professor").isEqualTo("well kempt");
        // no need to call assertAll, it is done when softly is closed.
   }
 }

    Now upon running the test our JUnit exception message is far more detailed: 

     org.assertj.core.api.SoftAssertionError: The following 4 assertions failed:
 1) [Living Guests] expected:<[7]> but was:<[6]>
 2) [Library] expected:<'[clean]'> but was:<'[messy]'>
 3) [Candlestick] expected:<'[pristine]'> but was:<'[bent]'>
 4) [Professor] expected:<'[well kempt]'> but was:<'[bloodied and disheveled]'>

    Aha! It appears that perhaps the Professor used the candlestick to perform the nefarious deed in the library. We should let the police take it from here.

    SoftAssertions works by providing you with proxies of the AssertJ assertion objects (those created by Assertions#assertThat...) whose assertion failures are caught and stored. Only when you call SoftAssertions.assertAll() will a SoftAssertionError be thrown containing the error messages of those previously caught assertion failures.

    Note that because SoftAssertions is stateful you should use a new instance of SoftAssertions per test method. Also, if you forget to use try-with-resources statement, the test will pass even if any assertion objects threw exceptions (because they're proxied, remember?). So don't forget.

    It is recommended to use AbstractAssert.as(String, Object...) so that the multiple failed assertions can be easily distinguished from one another.

    Author:
    Brian Laframboise
    See Also:
    Reinventing Assertions (inspired this feature)