如何使用JUnit4测试maven插件

Question

I'm writing a maven plugin and want to write some JUnit tests. I followed the description in Maven Plugin Testing . Unfortunately I keep getting an Exception during set-up of the test, before I can configure or invoke anything.

This is my JUnit test code:

public class ResetMojoTest {

    private static final String POM_FILE_NAME = "/path/to/pom.xml"; 

    @Rule
    public MojoRule rule = new MojoRule();

    @Test
    public void testSomething()
        throws Exception
    {
        File pom = new File(POM_FILE_NAME);
        Assert.assertNotNull( pom );
        Assert.assertTrue( pom.exists() );

        ResetMojo resetMojo = (ResetMojo) rule.lookupMojo( "touch", pom );
        Assert.assertNotNull( resetMojo );
        resetMojo.execute();
    }

}

And this is the stack trace of the exception:

java.io.IOException: Stream closed
    at java.io.BufferedInputStream.getInIfOpen(BufferedInputStream.java:134)
    at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
    at java.io.BufferedInputStream.read(BufferedInputStream.java:237)
    at org.apache.commons.io.input.BOMInputStream.getBOM(BOMInputStream.java:175)
    at org.apache.commons.io.input.BOMInputStream.getBOMCharsetName(BOMInputStream.java:201)
    at org.apache.commons.io.input.XmlStreamReader.doRawStream(XmlStreamReader.java:412)
    at org.apache.commons.io.input.XmlStreamReader.<init>(XmlStreamReader.java:206)
    at org.apache.commons.io.input.XmlStreamReader.<init>(XmlStreamReader.java:171)
    at org.apache.commons.io.input.XmlStreamReader.<init>(XmlStreamReader.java:140)
    at org.apache.maven.plugin.testing.AbstractMojoTestCase.setUp(AbstractMojoTestCase.java:119)
    at org.apache.maven.plugin.testing.MojoRule$2.evaluate(MojoRule.java:299)
    at org.junit.rules.RunRules.evaluate(RunRules.java:20)

Any ideas about how to get this working?

Answer 1

Also experiencing this issue. The mojo rule fails, because it instantiates a an anonymous implementation of AbstractMojoTestCase , which then looks for which then attempts to create an input stream loading data here: InputStream is = getClass().getResourceAsStream( "/" + getPluginDescriptorLocation() ); . This ( getPluginDescriptorLocation() ) is just a hard-coded file string "META-INF/maven/plugin.xml" .

I resolved this by adding the following dependency:

<dependency>
  <groupId>org.apache.maven</groupId>
  <artifactId>maven-compat</artifactId>
  <version>3.5.0</version>
</dependency>

I'm not sure why this fixes the issue. The file still doesn't exist (I've checked both original sources and target directories and it's not in either). So additional searching will be needed to figure out why this works.

Here's my dependencies for reference.

<dependency>
  <groupId>org.apache.maven</groupId>
  <artifactId>maven-plugin-api</artifactId>
  <version>3.5.0</version>
</dependency>
<dependency>
  <groupId>org.twdata.maven</groupId>
  <artifactId>mojo-executor</artifactId>
  <version>2.3.0</version>
</dependency>
<dependency>
  <groupId>org.apache.maven.plugin-tools</groupId>
  <artifactId>maven-plugin-annotations</artifactId>
  <version>3.5</version>
  <scope>provided</scope>
</dependency>
<dependency>
  <groupId>org.eclipse.aether</groupId>
  <artifactId>aether-api</artifactId>
  <version>1.1.0</version>
</dependency>
<dependency>
  <groupId>org.apache.maven</groupId>
  <artifactId>maven-core</artifactId>
  <version>3.5.0</version>
</dependency>
<dependency>
  <groupId>org.apache.maven</groupId>
  <artifactId>maven-compat</artifactId>
  <version>3.5.0</version>
</dependency>
<!--Test Dependencies-->
<dependency>
  <groupId>junit</groupId>
  <artifactId>junit</artifactId>
  <version>4.12</version>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.apache.maven.plugin-testing</groupId>
  <artifactId>maven-plugin-testing-harness</artifactId>
  <version>3.3.0</version>
  <scope>test</scope>
</dependency>

Answer 2

Got the same issue. Solved it by adding the right dependencies. Important is that the dependencies marked as provided by the harness maven plugin are added to test scope:

<properties>
  <dependency.maven.version>3.3.9</dependency.maven.version>
  <!-- and others -->
</properties>

<dependencies>
  <!-- your dependencies -->

  <!-- maven plugin dependencies -->
  <dependency>
    <groupId>org.apache.maven</groupId>
    <artifactId>maven-plugin-api</artifactId>
    <version>${dependency.maven.version}</version>
  </dependency>
  <dependency>
    <groupId>org.apache.maven</groupId>
    <artifactId>maven-core</artifactId>
    <version>${dependency.maven.version}</version>
  </dependency>
  <dependency>
    <groupId>org.apache.maven</groupId>
    <artifactId>maven-model</artifactId>
    <version>${dependency.maven.version}</version>
  </dependency>
  <dependency>
    <groupId>org.apache.maven</groupId>
    <artifactId>maven-artifact</artifactId>
    <version>${dependency.maven.version}</version>
  </dependency>

  <!-- test dependencies -->
  <dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>${dependency.junit.version}</version>
    <scope>test</scope>
  </dependency>
  <dependency>
    <groupId>org.apache.maven.plugin-testing</groupId>
    <artifactId>maven-plugin-testing-harness</artifactId>
    <version>3.3.0</version>
    <scope>test</scope>
  </dependency>
  <dependency>
    <groupId>org.apache.maven</groupId>
    <artifactId>maven-aether-provider</artifactId>
    <version>${dependency.maven.version}</version>
    <scope>test</scope>
  </dependency>
  <dependency>
    <groupId>org.apache.maven</groupId>
    <artifactId>maven-compat</artifactId>
    <version>${dependency.maven.version}</version>
    <scope>test</scope>
  </dependency>

  <!-- provided maven dependencies -->
  <dependency>
    <groupId>org.apache.maven.plugin-tools</groupId>
    <artifactId>maven-plugin-annotations</artifactId>
    <version>3.3</version>
    <scope>provided</scope>
  </dependency>

</dependencies>

And your Test class should look like

public class YourMojoTest {

  @Rule
  public MojoRule rule = new MojoRule();

  @Test
  public void shouldExecuteMojo() throws Exception {
    // given
    File testPom = new File(PlexusTestCase.getBasedir(), "src/test/resources/pom.xml");

    final Properties properties = new Properties();
    final MavenProject mavenProject = Mockito.mock(MavenProject.class);
    Mockito.when(mavenProject.getProperties()).thenReturn(properties);

    // when
    YourMojo mojo = (YourMojo) rule.lookupMojo("fetch", testPom);
    assertNotNull(mojo);
    mojo.setProject(mavenProject);
    mojo.execute();

    // then
    // do your tests ...
  }
}

Hope this helps for other struggling with the same issue

Answer 3

The loading of the POM file does not look good:

The following code is from the examples:

File pom = rule.getTestFile( "src/test/resources/unit/project-to-test/pom.xml" );

and this is what you have:

File pom = new File(POM_FILE_NAME);

Apart from this you have a different location which looks like this:

private static final String POM_FILE_NAME = "/path/to/pom.xml"; 

But the location of the pom file should be:

private static final String POM_FILE_NAME = "src/test/resources/pom.xml";