JUnit測試中的“ Singleton”

Question

我已經使用兩年了，現在我正在嘗試學習TDD（測試驅動開發）和JUnit， FizzBu​​zz Kata似乎是一個不錯的起點。 所以我做到了：

public class FizzBuzz {
    public static void main(String[] args) {
        Generator generator = new Generator();
        List<String> numbers = generator.fill(1, 100);
        numbers.forEach( item -> System.out.println(item) );
    }
}

現在可以找到它了，關於我的GeneratorTest.java有一個問題：

public class GeneratorTest {
@Test
public void checkFizz() {
    //Arrange
    Generator generator = new Generator(); // This line is on every test!

    //Act
    final int fizzNumber = 3;
    final int containsFizz = 13;

    final String result1 = generator.transform(fizzNumber);
    final String result2 = generator.transform(containsFizz);

    // Assert
    assertEquals("Fizz", result1);
    assertEquals("Fizz", result2);
}

@Test
public void checkBuzz() {
    //Arrange
    Generator generator = new Generator(); // This line is on every test!

    //Act
    final int buzzNumber = 5;
    final int containsBuzz = 52;

    final String result1 = generator.transform(buzzNumber);
    final String result2 = generator.transform(containsBuzz);

    // Assert
    assertEquals("Buzz", result1);
    assertEquals("Buzz", result2);
}

@Test
public void checkFizzBuzz() {
    //Arrange
    Generator generator = new Generator(); // This line is on every test!

    //Act
    final int fizzBuzzNumber = 15;
    final int containsFizzBuzz = 53;

    final String result1 = generator.transform(fizzBuzzNumber);
    final String result2 = generator.transform(containsFizzBuzz);

    // Assert
    assertEquals("FizzBuzz", result1);
    assertEquals("FizzBuzz", result2);
}

@Test
public void checkFillSize() {
    //Arrange
    Generator generator = new Generator(); // This line is on every test!

    //Act
    final int lowerBound = 2;
    final int upperBound = 100;
    final int expectedSize = upperBound - lowerBound + 1;
    List<String> filledList = generator.fill(lowerBound, upperBound);

    //Assert
    assertEquals(expectedSize, filledList.size() );
}

@Test
public void checkFillContents() {
    //Arrange
    Generator generator = new Generator(); // This line is on every test!

    //Act
    ArrayList<String> expectedList = new ArrayList<>( Arrays.asList("1", "2", "Fizz", "4", "Buzz", "Fizz", "7", "8", "Fizz", "Buzz", "11", "Fizz", "Fizz", "14", "FizzBuzz", "16", "17", "Fizz", "19", "Buzz", "Fizz", "22", "Fizz", "Fizz", "Buzz", "26", "Fizz", "28", "29", "FizzBuzz") ) ;
    List<String> filledList = generator.fill(1, expectedList.size() );

    //Assert
    assertEquals(expectedList, filledList);
}

@Test
public void checkFillCrossedBounds() {
    //Arrange
    Generator generator = new Generator(); // This line is on every test!

    //Act
    final int lowerBound = 100;
    final int upperBound = 1;
    final int expectedSize = 0;
    List<String> filledList = generator.fill(lowerBound, upperBound);

    //Assert
    assertEquals(expectedSize, filledList.size() );
}

有沒有辦法制作單例generator ？ 如果是這樣，這是一個好習慣嗎？

我曾考慮過在構造函數中執行此操作，但是我不確定這是否是“正確”的方法，因為我對JUnit和TDD相當陌生。

PS：來自西班牙的問候！

Answer 1

我同意JB Nizet的觀點，每個測試彼此獨立。

因此，您的類Generator一定不能是單例。
我不太了解Java，但是在每個測試運行器中，您都可以使用以下方法：

• 之前
• 事后
• 事前
• 畢竟

例如，您的行Generator generator = new Generator(); 可 ：

public class GeneratorTest {
    private Generator generator = null

    @Before
    public void runBeforeEachMethod() {
       this.generator = new Generator();
    }

    // your tests
}

因此，對於每個測試，您都有一個Generator的新實例。 您也可以使用BeforeAll ，但是更改生成器的狀態可能會導致一些不良的副作用，從而使測試失敗。

您可以查看以下文檔： https : //www.mkyong.com/unittest/junit-4-tutorial-1-basic-usage/