REDI-95: ViewModel unit tests (JUnit5 + Turbine + AssertK + fakes)

Test CharacterListViewModel and CharacterDetailViewModel entirely through their MVI surface with a FakeCharacterRepository (a fake, not a mock) and a directly constructed SavedStateHandle, on StandardTestDispatcher. Coverage: happy path, error -> UiText + snackbar Event, pagination end-reached, the in-flight and duplicate next-page guards, process-death restore, and both branches of OnRetry. Also a domain test for GetCharactersPageUseCase (delegation + error propagation).
2026-06-10 15:00:45 +02:00
parent 7a7ab45a66
commit 3f9cf96216
4 changed files with 483 additions and 0 deletions
--- a/feature/characters/domain/src/test/kotlin/com/example/architecture/feature/characters/domain/usecase/GetCharactersPageUseCaseTest.kt
+++ b/feature/characters/domain/src/test/kotlin/com/example/architecture/feature/characters/domain/usecase/GetCharactersPageUseCaseTest.kt
@@ -0,0 +1,79 @@
+package com.example.architecture.feature.characters.domain.usecase
+
+import assertk.assertThat
+import assertk.assertions.isEqualTo
+import assertk.assertions.isInstanceOf
+import com.example.architecture.core.domain.DataError
+import com.example.architecture.core.domain.Result
+import com.example.architecture.feature.characters.domain.CharacterRepository
+import com.example.architecture.feature.characters.domain.model.Character
+import com.example.architecture.feature.characters.domain.model.CharacterDetails
+import com.example.architecture.feature.characters.domain.model.CharacterStatus
+import com.example.architecture.feature.characters.domain.model.CharactersPage
+import kotlinx.coroutines.runBlocking
+import org.junit.jupiter.api.Test
+
+/**
+ * Tests for the (thin pass-through) [GetCharactersPageUseCase]: it must forward the requested page to
+ * the repository and return its result verbatim — success and error alike. Pure JVM test on the
+ * JUnit 5 platform (see DomainModuleConventionPlugin); collaborator is a hand-written fake.
+ */
+class GetCharactersPageUseCaseTest {
+
+    @Test
+    fun `returns the repository page on success`() = runBlocking {
+        val page = CharactersPage(characters = listOf(domainCharacter(1)), nextPage = 2)
+        val useCase = GetCharactersPageUseCase(FakeCharacterRepository(pageResult = Result.Success(page)))
+
+        val result = useCase(page = 1)
+
+        assertThat(result).isEqualTo(Result.Success(page))
+    }
+
+    @Test
+    fun `propagates the repository error`() = runBlocking {
+        val useCase = GetCharactersPageUseCase(
+            FakeCharacterRepository(pageResult = Result.Error(DataError.Network.SERVER_ERROR)),
+        )
+
+        val result = useCase(page = 1)
+
+        assertThat(result).isInstanceOf(Result.Error::class)
+        assertThat((result as Result.Error).error).isEqualTo(DataError.Network.SERVER_ERROR)
+    }
+
+    @Test
+    fun `forwards the requested page number`() = runBlocking {
+        val fake = FakeCharacterRepository(
+            pageResult = Result.Success(CharactersPage(characters = emptyList(), nextPage = null)),
+        )
+        val useCase = GetCharactersPageUseCase(fake)
+
+        useCase(page = 7)
+
+        assertThat(fake.lastRequestedPage).isEqualTo(7)
+    }
+
+    private class FakeCharacterRepository(
+        private val pageResult: Result<CharactersPage, DataError>,
+    ) : CharacterRepository {
+        var lastRequestedPage: Int? = null
+            private set
+
+        override suspend fun getCharacters(page: Int): Result<CharactersPage, DataError> {
+            lastRequestedPage = page
+            return pageResult
+        }
+
+        override suspend fun getCharacterDetails(id: Int): Result<CharacterDetails, DataError> =
+            Result.Error(DataError.Network.NOT_FOUND)
+    }
+
+    private fun domainCharacter(id: Int) = Character(
+        id = id,
+        name = "Character $id",
+        status = CharacterStatus.ALIVE,
+        species = "Human",
+        imageUrl = "https://example.com/$id.png",
+    )
+}