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JUnit4 Rules

A collection of useful test rules for multiple use cases

RetryTestRule

This rule can be useful for end-to-end tests that have some degree of tolerable flakiness.

Avoid using it for all sorts of tests!

Total executions = [1, 1 + times], depends on which execution the test actually passes

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@RetryTest(times = 9)
class SampleRetryTest {

    // Make sure that this rule starts before any other rule
    @get:Rule(order = 0)
    val retryRule = RetryTestRule()

    @RetryTest(times = 2)
    @Test
    fun testExampleMethod() {
        // This test will be executed 3 times in the worst case
    }

    @Test
    fun testExampleClass() {
        // This test will be executed 10 times in the worst case
    }
}

RepeatTestRule

This rule is useful to check for test flakiness. Use it carefully and do not commit code with these.

Total executions = 1 + times

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@RepeatTest(times = 2)
class SampleRepeatTest {

    // Make sure that this rule starts before any other rule
    @get:Rule(order = 0)
    val repeatRule = RepeatTestRule()

    @RepeatTest(times = 99)
    @Test
    fun `this test will execute 100 times`() {
        // Number of times is defined by the method annotation
    }

    @Test
    fun `this test will execute 3 times`() {
        // Number of times is defined by the class annotation
    }

}

MainDispatcherRule

As seen here:

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class ViewModelTest {

    @get:Rule
    val mainDispatcherRule = MainDispatcherRule()

    @Test
    fun `this test replaces Dispatchers.Main for ViewModels`() = runTest {
        // given
        val viewModel = TestViewModel()

        // when
        viewModel.load()

        // then
        assertThat(viewModel.uiState).isNotNull()
    }
}

TestDescriptionRule

A rule for extracting metadata for the current test being executed.

class SampleTest {

    @get:Rule
    val testDescriptionRule = TestDescriptionRule()

    @Test
    fun `test example`() {
        val description = testDescriptionRule.getDescription()
        assertThat(description.methodName).isEqualTo("test example")
    }

}