java - JUnit 测试上的 "Singleton"

Question

我已经使用了两年了，现在我正在尝试学习 TDD(测试驱动开发)和 JUnit，FizzBuzz Kata看起来是一个不错的起点。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) );
    }
}

现在可以找到了，我有一个关于我的 GeneratorTest.java 的问题:

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() );
}

有没有办法制作一个单例生成器？如果是这样，这是一个好的做法吗？

我想过在构造函数中执行此操作，但是我不确定这是否是“正确”的方法，因为我对 JUnit 和 TDD 还很陌生。

PS:来自西类牙的问候!

Answer 1

我同意 JB Nizet 的观点，每个测试都是相互独立的。

因此，您的类生成器一定不能是单例。
我不太了解 Java，但是在每个测试运行器中都有一些方法，例如:

• 每个之前
• 每次之后
• 之前
• 毕竟

例如，您的行 Generatorgenerator = new Generator(); 可以是:

public class GeneratorTest {
    private Generator generator = null

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

    // your tests
}

因此，对于每个测试，您都有一个 Generator 的新实例。您也可以使用 BeforeAll，但是更改生成器的状态可能会导致一些不良副作用，从而导致测试失败。

您可以查看此文档:https://www.mkyong.com/unittest/junit-4-tutorial-1-basic-usage/