Parameters on BeforeClass

[devkhan]

Current Scenario: I initialize some variables in BeforeClass method and keep them as members. Since, I do some processing on files, to optimize tests, I just do them once in the @BeforeClass method, and have asserts in different tests.

Requirement: I want to test multiple files, and hence was thinking may be there is some way I can call BeforeClass with each file and call all of the tests again with the new members.

Is there any way to do this? Maybe some class level params?

[devkhan]

Update: I digged a bit more and faced a java.lang.IllegalArgumentException: wrong number of arguments in class configuration.

This happened while trying to pass params to @BeforeClass methods.

[jrmichael]

JUnitParams supports parameterization only of test methods.

@BeforeClass is meant to be a one time action that is supposed to prepare system for tests. I think parameterizing it is not a good idea.

In your case I would suggest to creata a method that provides all the parameters (file names) and use it in your BeforeClass preparation and as a parameters provider for tests. @Parameters(method="myMethodReturningListOfFiles")

[devkhan]

I get this, but the issue is if I do this, then all of my tests will repeat the file processing which can be just done at a class(or instance) level. That is why I was initializing members in @BeforeClass.

Anyway, I guess that is by JUnit's design, I'd have to try something else. Thanks.

[jrmichael]

Maybe this snippet will help you

@RunWith(JUnitParamsRunner.class)
public class MyTestClass {

    private static File[] files;

    @BeforeClass
    public static void prepareFiles() {
        files = loadMyFiles("file1", "file2");
    }

    public File[] getFiles() {
        return files;
    }

    @Test
    @Parameters(method = "getFiles")
    public void doSomeTesting(File file) {
        //testing...
    }
}

EDIT: this snippet won't work - @BeforeClass is called during test execution and parameters are evaluated earlier

[devkhan]

Thanks, I'm doing something similar to this. I assume you mean @BeforeClass there (instead of @BeforeEach, right?

[devkhan]

There's one issue, though. According to your snippet, getFiles is called before prepareFiles defeating the purpose of initializing member variables.

[jrmichael]

Oh right.
We cannot call @BeforeClass blocks before parameters calculation. It is a part of test execution, while parameters calculation has to happen earlier in order to establish amount of tests and their description.

Sorry, but you will have to try a different approach.

[devkhan]

I thought so. For now I'm just using indexes instead of actual objects and initializing them in @BeforeClass like previously.