Simplify JUnit tests with custom annotations

In the beginning was a test, that provided to be vital, but not sufficient. In modern application development we encounter:

• Unit Tests: testing a single function or a tuple of related functions
• Module Tests: testing bigger parts of your application, without actual external dependencies
• Integration or End-to-End tests: a.k.a life firing exercise

This entry isn't a discussion about the merits of how much and when test, but making tests easy to setup and distinguish

The manual way

We typically use Mockito, vert.x and REST-assured in our tests, so a typical test class would look like this:

@ExtendWith(VertxExtension.class, MockitoExtension.class, MyCustomExtension.class})
@Tag("UnitTest")
class SomethingTest {

  @Test
  does_it_blend() {
    // Test goes here
  }
}

It is just two lines, but everywhere. You can simplify it by creating your own annotation.

The custom annotation

@Target({TYPE, METHOD, ANNOTATION_TYPE})
@Retention(RUNTIME)
@ExtendWith({VertxExtension.class, MockitoExtension.class, MyCustomExtension.class})
@Tag("UnitTest")
public @interface UnitTest {
  // no action needed here, JUnit use only!
}

Now you simply use:

@UnitTest
class SomethingTest {

  @Test
  does_it_blend() {
    // Test goes here
  }
}

While this looks like minor cosmetic, it allows to control test extensions from a single place, your annotation source. Repeat that process for the other test types (ModuleTests, IntegrationTests, PerformanceTests etc.) you want to use.

In your pom.xml, in the build-plugins section you can use the tag to ensure all your unit test, but only them execute on mvn test and the others on mvn verify

<plugin>
  <!-- Run UNIT and MODULE tests, no backend calls -->
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <configuration>
    <groups>UnitTest,ModuleTest</groups>
  </configuration>
</plugin>

As usual YMMV