c# - 如何用 FluentAssertions 替换 Assert.Fail()

Question

我们目前正在转换一些使用 Assert.IsTrue()、Assert.AreEqual()、Assert.IsNotNull() 的代码等 C# 的基本单元测试断言库

我们想使用 FluentAssertions，比如 value.Should().BeNull()。

我在某些位置使用 Assert.Fail() 进行了一些测试。我应该使用什么来有效地替换它们，因为我们想要取消每一个“Assert.*”，而我在 FluentAssertions 中找不到等效项？

举个例子

[TestMethod, TestCategory("ImportantTest")]
public void MethodToTest_Circumstances_ExpectedResult()
{
    // Arrange
    var variable1 = new Type1() { Value = "hello" };
    var variable2 = new Type2() { Name = "Bob" };

    // Act
    try
    {
        MethodToTest(variable1, variable2);
        // This method should have thrown an exception
        Assert.Fail();
    }
    catch (Exception ex)
    {
        ex.Should().BeOfType<DataException>();
        ex.Message.Should().Be(Constants.DataMessageForMethod);
    }

    // Assert
    // test that variable1 was changed by the method
    variable1.Should().NotBeNull();
    variable1.Value.Should().Be("Hello!");
    // test that variable2 is unchanged because the method threw an exception before changing it
    variable2.Should().NotBeNull();
    variable2.Name.Should().Be("Bob");
}

Answer 1

重组测试以利用 .ShouldThrow<>断言扩展。

[TestMethod, TestCategory("ImportantTest")]
public void MethodToTest_Circumstances_ExpectedResult() {
    // Arrange
    var variable1 = new Type1() { Value = "hello" };
    var variable2 = new Type2() { Name = "Bob" };

    // Act
    Action act = () => MethodToTest(variable1, variable2);       

    // Assert
    // This method should have thrown an exception
    act.ShouldThrow<DataException>()
       .WithMessage(Constants.DataMessageForMethod);
    // test that variable1 was changed by the method
    variable1.Should().NotBeNull();
    variable1.Value.Should().Be("Hello!");
    // test that variable2 is unchanged because the method threw an exception before changing it
    variable2.Should().NotBeNull();
    variable2.Name.Should().Be("Bob");
}

在上面的例子中，如果没有抛出预期的异常，断言就会失败，停止测试用例。

您应该查看 documentation on asserting exceptions更好地了解如何使用该库。