Maven: The Definitive Guide

Executing Unit Tests

Now that your project has unit tests, let’s run them. You don’t have to do anything special to run a unit test; the test phase is a normal part of the Maven lifecycle. You run Maven tests whenever you run mvn package or mvn install. If you would like to run all the lifecycle phases up to and including the test phase, run mvn test:

$ mvn test
...
[INFO] [surefire:test]
[INFO] Surefire report directory: ~/examples/simple-weather/target/\
                                  surefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running org.sonatype.mavenbook.weather.yahoo.WeatherFormatterTest
0    INFO  YahooParser  - Creating XML Reader
177  INFO  YahooParser  - Parsing XML Response
239  INFO  WeatherFormatter  - Formatting Weather Data
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.547 sec
Running org.sonatype.mavenbook.weather.yahoo.YahooParserTest
475  INFO  YahooParser  - Creating XML Reader
483  INFO  YahooParser  - Parsing XML Response
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.018 sec

Results :

Tests run: 2, Failures: 0, Errors: 0, Skipped: 0

Executing mvn test from the command line causes Maven to execute all lifecycle phases up to the test phase. The Maven Surefire plugin has a test goal that is bound to the test phase. This test goal executes all of the unit tests that this project can find under src/test/java. In the case of this project, you can see that the Surefire plugin’s test goal executes WeatherFormatterTest and YahooParserTest. When the Surefire plugin runs the JUnit tests, it also generates XML and text reports in the ${basedir}/target/surefire-reports directory. If your tests are failing, you should look in this directory for details such as stack traces and error messages generated by your unit tests.

Ignoring Test Failures

You will often find yourself developing on a system that has failing unit tests. If you are practicing Test-Driven Development (TDD), you might use test failure as a measure of how close your project is to completeness. If you have failing unit tests, and you would still like to produce build output, you are going to have to tell Maven to ignore build failures. When Maven encounters a build failure, its default behavior is to stop the current build. To continue building a project even when the Surefire plugin encounters failed test cases, you’ll need to set the testFailureIgnore configuration property of the Surefire plugin to true. See Example 4-16.

Example 4-16. Ignoring unit test failures

<project>
  [...]
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <configuration>
          <testFailureIgnore>true</testFailureIgnore>
        </configuration>
      </plugin>
    </plugins>
  </build>
  [...]
</project>

The plugin documents (http://maven.apache.org/plugins/maven-surefire-plugin/test-mojo.html) show that this parameter declares an expression, as shown in Example 4-17.

Example 4-17. Plugin parameter expressions

    testFailureIgnore  Set this to true to ignore a failure during \
                          testing. Its use is NOT RECOMMENDED, but quite \
                          convenient on occasion.

    * Type: boolean
    * Required: No
    * Expression: ${maven.test.failure.ignore}

This expression can be set from the command line using the -D parameter:

$ mvn test -Dmaven.test.failure.ignore=true

Skipping Unit Tests

You may want to configure Maven to skip unit tests altogether. Maybe you have a very large system where the unit tests take minutes to complete and you don’t want to wait for them before producing output. Or maybe you are working with a legacy system that has a series of failing unit tests, and instead of fixing them, you just want to produce a JAR. Maven allows you to skip unit tests using the skip parameter of the Surefire plugin. To skip tests from the command line, simply add the maven.test.skip property to any goal:

$ mvn install -Dmaven.test.skip=true
...
[INFO] [compiler:testCompile]
[INFO] Not compiling test sources
[INFO] [surefire:test]
[INFO] Tests are skipped.
...

When the Surefire plugin reaches the test goal, it will skip the unit tests if the maven.test.skip properties is set to true. Another way to configure Maven to skip unit tests is to add the configuration shown in Example 4-18 to your project’s pom.xml. To do this, you would add a plugin element to your build configuration.

Example 4-18. Skipping unit tests

<project>
  [...]
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <configuration>
          <skip>true</skip>
        </configuration>
      </plugin>
    </plugins>
  </build>
  [...]
</project>