Using stubs in a basic Java maven project

Question

I have a basic maven project with the folder structure: -main and -test directories.

I have one package in the main source directory which consists of a few classes, say a.class b.class and c.class, all under the same package. All classes have dependencies to each other. To do proper unit testing, and to cut the dependencies from each class, I write stub classes of each a, b and c class, define them to have the same package and put them inside the test source directory. Then I run: mvn test

Fine, the stubs are now being found first from the classpath and used, but I want to modify the classpath (on the fly?) so that, when testing class a, I need to have the original a.class and stubs used for b.class and c.class. Similarly, when testing class b, I need to have the original class b and stubs used for a.class and c.class.

How do I accomplish this using Maven and JUnit?

This is kind of frustrating in Java, because in C++, one can use the makefile source path and user defined include paths in unit test header files to force the stubs to be found first and then explicitly add an include to the original class to be tested.

Answer 1

Like @khmarbaise already pointed out you are going the wrong way. In Java it is good practice to use Mocking libraries like Mockito and PowerMock if you want to test static methods.

Those libraries help you to write Stubs for your existing classes without to modify the classes themselves. Check Maven Central for Mockito. You can include it with maven via

<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-core</artifactId>
    <version>1.10.19</version>
    <scope>test</scope>
</dependency>

Then using JUnit you end up writing Mocks for your existing classes. There are many tutorials regarding Mockito out there.

Answer 2

If you have dependent classes you schould use interface for each class. Then you can resolve dependency problems actually...