[Android/Jetpack Compose] how to use `context` in Unit test?

You may want to use context in your unit test in jetpack. But if you do nothing you may get error some kinds of context.

Hey, how do I use context in the unit test?

There is an easy way to use it. This is Robolectric.

You have to solve dependency about Robolectric in the module level build.gradle.kt.

(I use version catalogs for the version management.)

    testImplementation(libs.robolectric)

Next, you prepare the DispatcherRule for validating test modules. The following code is just a minimum example.

@OptIn(ExperimentalCoroutinesApi::class)
class MainDispatcherRule(
    private val testDispatcher: TestDispatcher = UnconfinedTestDispatcher(),
) : TestWatcher() {
    override fun starting(description: Description) {
        Dispatchers.setMain(testDispatcher)
    }

    override fun finished(description: Description) {
        Dispatchers.resetMain()
    }
}

Finally, put the annotaion on your test class.

@RunWith(RobolectricTestRunner::class)
class SomeTest {
// continue the test code...