JUnit λ

JUnit extensions build on Java 8 lambdas. A JDK level of 1.8 is required.

Assertions

Simple assertions can be made like such:

    assertVoidRaises(() -> anObject.aMethod(anArgument), IllegalArgumentException.class);
    assertRaises(() -> { return (String) Integer.valueOf(5); }, ClassCastException.class);
    assertForAll(Arrays.asList(1, 2, 3), i -> i < 4);
    assertForAll(anyMapWithNumbersAsValues, n -> n >= 0);
    assertThat("Hello World", s -> s.matches("[\\w\\s]*"));

To get more informative descriptions of failed lambda methods you may use the $$(String description, Predicate<T> predicate) factory method:

    assertForAll(Arrays.asList(1, 2, 3), $$("smaller than 4", i -> i < 4));
    assertThat("Hello World", $$("letters and spaces", s -> s.matches("[\\w\\s]*")));

To improve readability in some situations, rather than the @Test(expected = AssertionError.class) annotation for tests which are expected to fail assertFailure(Block block) can be used:

    assertFailure(() -> assertTrue(false));
    assertFailure("Why did this not fail? Oh, right.", () -> assertTrue(true));

Parallel Test Execution

JUnit λ comes with a JUnit Runner which will execute your tests in parallel, thereby improving test execution speed in many cases.

    @RunWith(ParallelJUnitTestRunner.class)
    public class Tests {
        // ...
    }

This can be used with any JUnit tests, independent of whether they use lambda expressions or not.

Maven Dependency

Currently this version is not available on Maven Central. A previous version can received by the following dependency entry:

<dependency>
    <groupId>com.github.marschall</groupId>
    <artifactId>junit-lambda</artifactId>
    <version>0.1.0</version>
</dependency>