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

Solution 1:

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.

Solution 2:

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.