edgelab-testing

name	edgelab-testing
description	Testing conventions, fake object patterns, and ViewModel test templates for the EdgeLab :presentation module. Load this skill before writing or modifying tests.

EdgeLab Testing Reference

Infrastructure

Aspect	Value
Framework	JUnit 4 + kotlin.test assertions
Coroutine testing	kotlinx-coroutines-test (runTest, StandardTestDispatcher, advanceUntilIdle)
Flow testing	Turbine 1.2.1 (available in :presentation)
Test doubles	Hand-written fakes. No MockK, no Mockito.
Source location	src/test/kotlin/ (note: kotlin/, not java/)

Fake Object Rules

• Implement the full interface
• Use MutableStateFlow for observable state
• Constructor parameters for configurable behavior (shouldFail, progressSteps, initialToken)
• Tracking booleans (initializeCalled, closeSessionCalled) when tests need to verify invocation
• Mark as internal class
• Shared fakes → TestFakes.kt. Simple one-off fakes → in the test file.

ViewModel Test Template

@OptIn(ExperimentalCoroutinesApi::class)
class XxxViewModelTest {
    private val testDispatcher = StandardTestDispatcher()

    @BeforeTest
    fun setup() {
        Dispatchers.setMain(testDispatcher)
    }

    @AfterTest
    fun tearDown() {
        Dispatchers.resetMain()
    }

    private fun createViewModel(): XxxViewModelImpl {
        return XxxViewModelImpl(
            // inject fakes here
            ioDispatcher = testDispatcher,  // CRITICAL
        )
    }

    @Test
    fun `SomeAction should update state`() = runTest {
        val viewModel = createViewModel()
        advanceUntilIdle()

        viewModel.onUiAction(UiAction.SomeAction("arg"))
        advanceUntilIdle()

        assertTrue(viewModel.uiState.value.someCondition)
        viewModel.dispose()  // ALWAYS dispose
    }
}

Critical Rules

• @OptIn(ExperimentalCoroutinesApi::class) on class
• Dispatchers.setMain(testDispatcher) in @BeforeTest
• Dispatchers.resetMain() in @AfterTest
• Pass testDispatcher as ioDispatcher in createViewModel()
• advanceUntilIdle() after creating ViewModel AND after each action
• viewModel.dispose() at end of EVERY test
• Use runTest { } (not runBlocking { })
• Use kotlin.test assertions (assertEquals, assertTrue)

Minimum Coverage for New Features

• Test initial UiState after creation
• Test each UiAction path (each when branch in onUiAction)
• Test at least one error/failure state
• Test reactive state updates (flow emission → UiState change)