I have created two classes:

@ExperimentalCoroutinesApi
open class InstantExecutorExtension : BeforeEachCallback, AfterEachCallback {

    override fun beforeEach(context: ExtensionContext?) {
        ArchTaskExecutor.getInstance()
            .setDelegate(object : TaskExecutor() {
                override fun executeOnDiskIO(runnable: Runnable) = runnable.run()

                override fun postToMainThread(runnable: Runnable) = runnable.run()

                override fun isMainThread(): Boolean = true
            })
    }

    override fun afterEach(context: ExtensionContext?) {
        ArchTaskExecutor.getInstance().setDelegate(null)
    }
}

and

@ExperimentalCoroutinesApi
class CoroutineExecutorExtension : InstantExecutorExtension() {

    private val testCoroutineDispatcher = TestCoroutineDispatcher()

    override fun beforeEach(context: ExtensionContext?) {
        super.beforeEach(context)
        Dispatchers.setMain(testCoroutineDispatcher)
    }

    override fun afterEach(context: ExtensionContext?) {
        super.afterEach(context)
        Dispatchers.resetMain()
        testCoroutineDispatcher.cleanupTestCoroutines()
    }
}

I'm using these classes to write unit tests for method that use coroutines and livedata. The problem I have is that I don't know how to share these classes in different modules. If I define them in the test folder then I can build the classes but they are not visible in other modules. If I define in the main folder there are compile time errors. What can I do to avoid having to define these classes in all the modules?

UPDATE To follow @Sam suggestion I have created a module that contains the two classes in the folder:

.\unittest\src\testFixtures\java\com\name\terminal\unittest

The build.gradle file of this module uses the plugins:

plugins {
    id 'com.android.library'
    id 'kotlin-android'
    id 'java-test-fixtures'
}

In the module where I want to use the CoroutineExecutorExtension I have imported the project of the unittest module with:

    testImplementation(testFixtures(project(":unittest")))

The problem is that the classes in the testFixtures folder are not visiible.

EDIT

This method does not work for an Android library. I can't use a java library because I need to be able to include Androidx dependencies.