Sharing src/test classes between modules in a multi-module maven project

I have a multi-module Maven project. For the sake of this example, consider two modules:

• data
• consumer

Module consumer has module data as a dependency.

Module data declares a bunch of core classes. There are tests under src/test that use them. These tests require some long-winded object creation, so I have a class with some utility methods in it to create these objects. This utility class (SampleDataHelper) is in the src/test hierarchy.

I also have some tests in the consumer module that need to create some of these long-winded objects. I want to use my SampleDataHelper class (defined in data src/test) in tests that reside in my consumer src/test tree. Unfortunately, even though data is a dependency of consumer, consumer can't see the classes that exist under data src/test.

To combat this, I thought I might create another module (data-test), and move SampleDataHelper to it under src/main. Then I would include data-test as a test scope dependency of data. Unfortunately, this introduces a circular dependency: data uses data-test, but data-test also requires data.

The only solution I've come up with is to place SampleDataHelper under data src/main under a test package and hope that no real application code ever calls it.

How can I share my SampleDataHelper class between modules without putting it under src/main?

Your Consumer project depends upon your Data project, therefore we are happy that Data must be built prior to Consumer. As a result, using the techniques suggested in the comments, I would ensure your Data project contains all the test code that you wish to share and configure the POM to produce a test JAR:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-jar-plugin</artifactId>
  <version>2.2</version>
  <executions>
    <execution>
      <goals>
        <goal>test-jar</goal>
      </goals>
    </execution>
  </executions>
</plugin>

Your Consumer project would then depend upon both the normal Data JAR artifact, plus the additional test-jar artifact, with test scope of course:

<dependency>
  <groupId>com.foo</groupId>
  <artifactId>data</artifactId>
  <version>1.0</version>
  <type>test-jar</type>
  <scope>test</scope>
</dependency>

I've used this approach on many occasions and it works well.

So the problem is that (some) tests in the data module depend on the SampleDataHelper class? You can move the SampleDataHelper class to src/main of the data-test module, if you at the same time move the tests (that depend on the specific class) to the src/test of the data-test module. Consequently, there would be no more circular dependencies.