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Java Unit Testing in Java What to Test Know Your Bounds

Phil Spelman
Phil Spelman
6,664 Points
Posted by Phil Spelman
Phil Spelman
6,664 Points

JUnit 5

Hi Craig! I was hoping you might add some notes or another video showing the differences between JUnit4 and JUnit5. A couple things I've run into is that they no longer support the @Test() parameter for expected exceptions, and that there is no longer support for @Rule annotations like with JUnit4.

If you end up putting together material on that I will for sure check it out!

3 Answers

Craig Dennis
STAFF
Craig Dennis
Treehouse Teacher
Craig Dennis
Craig Dennis
Treehouse Teacher

We were just talking about this. I've added it to the Java Content Trello Roadmap. Thanks Phil!

Arnór Kristmundsson
Arnór Kristmundsson
2,013 Points
Arnór Kristmundsson
Arnór Kristmundsson
2,013 Points

Hey, here is my solution for the overstockingIsNotAllowed() in jUnit 5:

    @Test
    void overstockingIsNotAllowed() throws Exception{
        assertThrows(IllegalArgumentException.class, () -> {
            bin.restock("Fritos", 2600, 100, 50);
        });
    }

but I was wondering, is it possible to check the error message in jUnit 5?

codeboost
codeboost
6,886 Points
codeboost
codeboost
6,886 Points

I guess this is a bit of a late reply, but yes, and there are multiple ways. The easiest I found is this one:

    @Test
    void overstockingIsNotAllowed() throws Exception{
        Exception exception = assertThrows(IllegalArgumentException.class, 
                () -> bin.restock("Fritos", 2600, 100, 50),
                "There are only 10 spots left");
        );
    }

For other people trying this out with junit5, @Rule doesn't exist anymore. Correct me if there's a better way, but it seems this is the junit 5 way:

import org.junit.jupiter.api.extension.ExtensionContext;
import org.junit.jupiter.api.extension.TestExecutionExceptionHandler;

class IllegalArgumentExceptionExpectedExtension implements TestExecutionExceptionHandler {
    @Override
    public void handleTestExecutionException(ExtensionContext extensionContext, Throwable throwable) throws Throwable {
        if (throwable instanceof IllegalArgumentException) {
            return;
        }

        throw throwable;
    }
}

And use it like this:

import org.junit.jupiter.api.extension.ExtendWith;

class BinTest {
    private Bin bin;

    @BeforeEach
    void setUp() {
        bin = new Bin(10);
    }

    @ExtendWith(IllegalArgumentExceptionExpectedExtension.class)
    @Test
    void overstockingNotAllowed() {
        bin.restock("Fritos", 2600, 100, 50);
    }
}

I'm not sure how to test the exception message with an extension.

Muhammad Nagy
Muhammad Nagy
944 Points
Muhammad Nagy
Muhammad Nagy
944 Points

In JUnit 5, the implementation should be like that

  @Test
  void overstockingNotAllowed() {
    IllegalArgumentException thrown =
        assertThrows(
            IllegalArgumentException.class,
            () -> {
              bin.restock("Fritos", 2600, 100, 50);
            });
    assertTrue(thrown.getMessage().equals("There are only 10 spots left"));
  }