Run JUnit tests from a dependency jar in Eclipse

Question

I have some JUnit tests that contained in a .jar that is intended to be used as a library. The library contains some tests that should be run whenever the library is used in another project.

However when I create a new project using the library and run JUnit on it in Eclipse then the tests in the dependency .jar don't run / don't get detected by the JUnit test runner. I get the message:

No tests found with test runner 'JUnit 4'.

Is there a way I can configure the dependency .jar so that the tests will run alongside any tests that might be contained in the main project?

Basically I want the dependency .jar to "export" the tests to whatever projects it is used in.

I'm using Eclipse Juno, JUnit 4.10, and Maven for the dependency management.

EDIT:

The point of this library is to be able to help test projects that use it - i.e. it runs some specialised tests. This is why I want to be able to import the library .jar and have it contribute the extra tests to the importing project.

Answer 1

You can try Maven Surefire.

In some cases it would be useful to have a set of tests that run with various dependency configurations. One way to accomplish this would be to have a single project that contains the unit tests and generates a test jar. Several test configuration projects could then consume the unit tests and run them with different dependency sets. The problem is that there is no easy way to run tests in a dependency jar. The Surefire plugin should have a configuration to allow me to run all or a set of unit tests contained in a dependency jar.

This can be done as follows (Junit 3):

Ensure test jar contains a class which has a static suite() method

import junit.framework.Test;
import junit.framework.TestSuite;

public class AllTests {    
    public static Test suite() 
    { 
        TestSuite suite = new TestSuite( "All Tests"); 
        suite.addTestSuite(TestOne.class); 
        suite.addTestSuite(TestTwo.class); 
        return suite; 
    }    
}

Then in the project using the test-jar dependency: create a TestCase:

package org.melati.example.contacts;
import org.melati.poem.AllExportedTests;
import junit.framework.Test;
import junit.framework.TestCase;

public class PoemTest extends TestCase {    
    public static Test suite() 
    { 
        return AllExportedTests.suite(); 
    }
}

Now the tests will be found.

Answer 2

I think that making a library of unit tests (@Test annotated methods) is a bad idea. However, making a library of reusable test components is a good one. We've done this in a few open source projects, and you can take a look how it works.

1. One Maven module exports test components (we call them "mocks"), from src/mock/java directory. Exported artifact has -mock classifier. See rexsl/pom.xml (pay attention to highlighted lines).

2. Mock artifacts are being deployed to Maven Central, together with usual artifacts: http://repo1.maven.org/maven2/com/rexsl/rexsl-core/0.3.8/ (pay attention to ...-mock.jar files)

3. Modules that need that mocks can include them as usual artifacts, for example rexsl-core/pom.xml (see highlighted lines):

4. Then, in your unit tests just use the classes from that mock libraries, like regular builders of mocks, for example: BulkHttpFeederTest

That's how you can make your test artifacts reusable, in an elegant way. Hope it helps.