annotation-processor-testing

An easy way to verify that your annotation processor is emitting the right diagnostics.

Setup

In order to use any of the test runners, you must include your test sources as a resource:

<build>
...
<testResources>
  <testResource>
    <directory>src/test/java/</directory>
  </testResource>
  <testResource>
    <directory>src/test/resources/</directory>
  </testResource>
</testResources>
...
</build>

Additionally, you may need to disable annotation processing during test compilation if you are testing ERROR diagnostics.

<build>
...
<plugins>
 <groupId>org.apache.maven.plugins</groupId>
 <artifactId>maven-compiler-plugin</artifactId>
 <executions>
   <execution>
     <id>default-testCompile</id>
     <goals>
       <goal>testCompile</goal>
     </goals>
     <configuration>
       <proc>none</proc>
     </configuration>
   </execution>
 </executions>
</plugins
...
</build>

Usage

Annotate your test class with @UseProcessor, @ExpectError, and @ExpectDiagnostic:

@UseProcessor(YourProcessor.class)
public class YourProcessorTest {
  @ExpectError @IncorrectlyUsedAnnotation
  public void method() {}

  @ExpectError("substring of the message") @IncorrectlyUsedAnnotation
  public void method1() {}

  @ExpectError(lineOffset = 1) // Expect a diagnostic on the next line.
  @IncorrectlyUsedAnnotation
  public void method2() {}

  @ExpectError(value = "[abc]+", regex = true) @IncorrectlyUsedAnnotation
  public void method3() {}

  @ExpectError(testName = "descriptive JUnit test name") @IncorrectlyUsedAnnotation
  public void method4() {}

  // No @Expect annotation needed.
  @CorrectlyUsedAnnotation
  public void method5() {}
}

JUnit 4

Add @RunWith(DiagnosticTester.class) to your test class.

JUnit 5

Ensure that annotation-processor-testing-junit5 is included as a dependency, and the JUnit 5 launcher should automatically discover your tests.