何时使用模拟框架？

Question

所以我正在玩我的单元测试的模拟框架(Moq),并且想知道何时应该使用模拟框架？

以下两个测试之间的好处/缺点是什么:

public class Tests
{
    [Fact]
    public void TestWithMock()
    {
        // Arrange
        var repo = new Mock<IRepository>();

        var p = new Mock<Person>();
        p.Setup(x => x.Id).Returns(1);
        p.Setup(x => x.Name).Returns("Joe Blow");
        p.Setup(x => x.AkaNames).Returns(new List<string> { "Joey", "Mugs" });
        p.Setup(x => x.AkaNames.Remove(It.IsAny<string>()));

        // Act
        var service = new Service(repo.Object);
        service.RemoveAkaName(p.Object, "Mugs");

        // Assert
        p.Verify(x => x.AkaNames.Remove("Mugs"), Times.Once());
    }

    [Fact]
    public void TestWithoutMock()
    {
        // Arrange
        var repo = new Mock<IRepository>();

        var p = new Person { Id = 1, Name = "Joe Blow", AkaNames = new List<string> { "Joey", "Mugs" } };

        // Act
        var service = new Service(repo.Object);
        service.RemoveAkaName(p, "Mugs");

        // Assert
        Assert.True(p.AkaNames.Count == 1);
        Assert.True(p.AkaNames[0] == "Joey");
    }
}

Answer 1

Use mock objects to truly create a unit test--a test where all dependencies are assumed to function correctly and all you want to know is if the SUT (system under test--a fancy way of saying the class you're testing) works.

The mock objects help to "guarantee" your dependencies function correctly because you create mock versions of those dependencies that produce results you configure. The question then becomes if the one class you're testing behaves as it should when everything else is "working."

Mock objects are particularly critical when you are testing an object with a slow dependency--like a database or a web service. If you were to really hit the database or make the real web service call, your test will take a lot more time to run. That's tolerable when it's only a few extra seconds, but when you have hundreds of tests running in a continuous integration server, that adds up really fast and cripples your automation.

This is what really makes mock objects important--reducing the build-test-deploy cycle time. Making sure your tests run fast is critical to efficient software development.

Answer 2

模拟框架用于消除依赖关系，因此单元测试将集中于要测试的“Unit”。在你的例子中，这个人看起来像一个简单的实体类，不需要使用 Mocking 。