Jetpack Compose 從心開始 Day13 - ViewModel 的單元測試

16th鐵人賽

kevin_chiu

團隊kotlin 研習團又來了

2024-09-23 02:42:30

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前言

    撰寫 ViewModel 的單元測試是確保 Android 應用程式品質的重要一環。透過測試，可以及早發現並修復問題，提高應用程式的穩定性。

為什麼要測試 ViewModel？

確保邏輯正確性： ViewModel 負責處理應用程式的業務邏輯，測試可以確保這些邏輯運作正確。
提早發現問題：在開發過程中及早發現並修復 bug，減少後期維護成本。
提高程式碼品質：測試驅動開發 (TDD) 可以幫助寫出更乾淨、更可維護的程式碼。

新增測試依附元件

在 app 的 build.gradle.kts

dependencies {

    ...
    implementation("androidx.lifecycle:lifecycle-viewmodel-compose:2.6.1")
    
    testImplementation("junit:junit:4.13.2")
    
    // Import the Compose BOM
    implementation(platform("androidx.compose:compose-bom:2023.06.01"))
    implementation("androidx.compose.material:material")
    implementation("androidx.compose.ui:ui")
    implementation("androidx.compose.ui:ui-tooling-preview")

    // ...
    androidTestImplementation(platform("androidx.compose:compose-bom:2023.06.01"))
    androidTestImplementation("androidx.compose.ui:ui-test-junit4")
}

建立測試

良好的單元測試通常具備下列四種屬性：

聚焦：將焦點放在測試單元，例如程式碼片段。這段程式碼通常是類別或方法。測試應聚焦於較小的程式碼，且應著重驗證個別程式碼的正確性，而非同時執行多段程式碼。
清楚易懂：程式碼應讀起來簡單易懂。開發人員一眼就能瞭解測試背後的意圖。
確定性：應一律通過或失敗。無論執行測試幾次，只要沒有對程式碼進行任何變更，測試應該都會產生相同的結果。測試不應凌亂，在某個執行個體中失敗，卻在另一個執行個體中成功，儘管沒有修改程式碼。
獨立模式：不需要人為操作或設定，就能獨立執行。

在專案的路徑(test) 新增測試程式

錯誤路徑單元測試

@Test
    fun gameViewModel_IncorrectGuess_ErrorFlagSet() {
        // Given an incorrect word as input
        val incorrectPlayerWord = "and"

        viewModel.updateUserGuess(incorrectPlayerWord)
        viewModel.checkUserGuess()

        val currentGameUiState = viewModel.uiState.value
        // Assert that score is unchanged
        assertEquals(0, currentGameUiState.score)
        // Assert that checkUserGuess() method updates isGuessedWordWrong correctly
        assertTrue(currentGameUiState.isGuessedWordWrong)
    }

測試 UI 的初始狀態

@Test
fun gameViewModel_Initialization_FirstWordLoaded() {
    val gameUiState = viewModel.uiState.value
    val unScrambledWord = getUnscrambledWord(gameUiState.currentScrambledWord)

    // Assert that current word is scrambled.
    assertNotEquals(unScrambledWord, gameUiState.currentScrambledWord)
    // Assert that current word count is set to 1.
    assertTrue(gameUiState.currentWordCount == 1)
    // Assert that initially the score is 0.
    assertTrue(gameUiState.score == 0)
    // Assert that the wrong word guessed is false.
    assertFalse(gameUiState.isGuessedWordWrong)
    // Assert that game is not over.
    assertFalse(gameUiState.isGameOver)
}

猜出所有字詞後測試 UI 狀態-正確

@Test
fun gameViewModel_AllWordsGuessed_UiStateUpdatedCorrectly() {
    var expectedScore = 0
    var currentGameUiState = viewModel.uiState.value
    var correctPlayerWord = getUnscrambledWord(currentGameUiState.currentScrambledWord)
    repeat(MAX_NO_OF_WORDS) {
        expectedScore += SCORE_INCREASE
        viewModel.updateUserGuess(correctPlayerWord)
        viewModel.checkUserGuess()
        currentGameUiState = viewModel.uiState.value
        correctPlayerWord = getUnscrambledWord(currentGameUiState.currentScrambledWord)
        // Assert that after each correct answer, score is updated correctly.
        assertEquals(expectedScore, currentGameUiState.score)
    }
    // Assert that after all questions are answered, the current word count is up-to-date.
    assertEquals(MAX_NO_OF_WORDS, currentGameUiState.currentWordCount)
    // Assert that after 10 questions are answered, the game is over.
    assertTrue(currentGameUiState.isGameOver)
}

測試執行個體生命週期總覽

@Test
    fun gameViewModel_Initialization_FirstWordLoaded() {
        
        val gameUiState = viewModel.uiState.value
        val unScrambledWord = getUnscrambledWord(gameUiState.currentScrambledWord)

        // Assert that current word is scrambled.
        assertNotEquals(unScrambledWord, gameUiState.currentScrambledWord)
        // Assert that current word count is set to 1.
        assertTrue(gameUiState.currentWordCount == 1)
        // Assert that initially the score is 0.
        assertTrue(gameUiState.score == 0)
        // Assert that wrong word guessed is false.
        assertFalse(gameUiState.isGuessedWordWrong)
        // Assert that game is not over.
        assertFalse(gameUiState.isGameOver)
    }