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简易扩展Visual Studio UnitTesting支持TestMethodCase

NUnit的TestCaseAttribute可以简化大量的测试参数输入用例的编写,如果基于Visual Studio Unit Test Project开发则默认没有类似的功能,看一段对比代码:

public class MyClass{    public Int32 DoWork(String name, Int32 n)    {        if (String.IsNullOrWhiteSpace(name))            throw new ArgumentOutOfRangeException("name");        if (n < 0)            throw new ArgumentOutOfRangeException("n");        return name.Length / n;    }}
[TestClass]public class MyClassTest{    [TestMethod]    public void DoWork()    {        var name = "test";        var n = 5;        var myClass = new MyClass();        var result = myClass.DoWork(name, n);        Assert.IsTrue(result == name.Length / n);    }    [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]    public void DoWork_NameIsNull()    {        var n = 5;        var myClass = new MyClass();        myClass.DoWork(null, n);    }    [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]    public void DoWork_NameIsEmpty()    {        var n = 5;        var myClass = new MyClass();        myClass.DoWork(String.Empty, n);    }    [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]    public void DoWork_NameIsWhiteSpace()    {        var n = 5;        var myClass = new MyClass();        myClass.DoWork(" ", n);    }    [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]    public void DoWork_NLessThanZero()    {        var name = "test";        var myClass = new MyClass();        myClass.DoWork(name, -1);    }}

可以发现为了测试参数输入验证是否达到预期的效果,额外编写了4个测试用例。如果使用NUnit的TestCase可以简化如下:

[TestFixture]public class MyClassTest{    [TestCase("Test", 5)]    [TestCase(null, 5, ExpectedException = typeof(ArgumentOutOfRangeException))]    [TestCase("", 5, ExpectedException = typeof(ArgumentOutOfRangeException))]    [TestCase(" ", 5, ExpectedException = typeof(ArgumentOutOfRangeException))]    [TestCase("Test", -1, ExpectedException = typeof(ArgumentOutOfRangeException))]    public void DoWork(String name, Int32 n)    {        var myClass = new MyClass();        var result = myClass.DoWork(name, n);        Assert.IsTrue(result == name.Length / n);    }}

要让Visual Studio Test支持类似的方式可以自己扩展,参考Visual Studio Team Test的Extending the Visual Studio Unit Test Type文章。不过我选择了更为简单的在原有的用例中扩展一个TestMethodCaseAttribute,例如:

[TestClass]public class MyClassTest{    [TestMethod]    [TestMethodCase("Test", 5)]    [TestMethodCase(null, 5, ExpectedException = typeof(ArgumentOutOfRangeException))]    [TestMethodCase("", 5, ExpectedException = typeof(ArgumentOutOfRangeException))]    [TestMethodCase(" ", 5, ExpectedException = typeof(ArgumentOutOfRangeException))]    [TestMethodCase("Test", -1, ExpectedException = typeof(ArgumentOutOfRangeException))]    public void DoWork()    {        TestMethodCaseHelper.Run(context =>         {            var name = context.GetArgument<String>(0);            var n = context.GetArgument<Int32>(1);            var myClass = new MyClass();            var result = myClass.DoWork(name, n);            Assert.IsTrue(result == name.Length / n);        });    }}

只要有一个TestMethodCase未通过,当前的TestMethod既为失败。使用这种方式进行Code Coverage统计并不受影响,可以正确评估

public static class TestMethodCaseHelper{    public static void Run(Action<TestMethodCaseContext> body)    {        var testMethodCases = FindTestMethodCaseByCallingContext();        foreach (var testMethodCase in testMethodCases)            RunTest(testMethodCase, body);    }    internal static IEnumerable<TestMethodCaseAttribute> FindTestMethodCaseByCallingContext()    {        var stackFrames = StackFrameHelper.GetCurrentCallStack();        var forTestFrame = stackFrames.FirstOrDefault(p => GetTestMethodCaseAttributes(p).Any());        return forTestFrame != null ? GetTestMethodCaseAttributes(forTestFrame) : new TestMethodCaseAttribute[0];    }    private static IEnumerable<TestMethodCaseAttribute> GetTestMethodCaseAttributes(StackFrame stackFrame)    {        return GetTestMethodCaseAttributes(stackFrame.GetMethod());    }    private static IEnumerable<TestMethodCaseAttribute> GetTestMethodCaseAttributes(MethodBase method)    {        return method.GetCustomAttributes(typeof(TestMethodCaseAttribute), true).OfType<TestMethodCaseAttribute>();    }    private static void RunTest(TestMethodCaseAttribute testMethodCase, Action<TestMethodCaseContext> body)    {        TestSettings.Output.WriteLine("Run TestMethodCase {0} started", testMethodCase.Name);        var stopwatch = Stopwatch.StartNew();        RunTestCore(testMethodCase, body);        stopwatch.Stop();        TestSettings.Output.WriteLine("Run TestMethodCase {0} finished({1})", testMethodCase.Name, stopwatch.ElapsedMilliseconds);    }    private static void RunTestCore(TestMethodCaseAttribute testMethodCase, Action<TestMethodCaseContext> body)    {        var testContext = new TestMethodCaseContext(testMethodCase);        if (testMethodCase.ExpectedException != null)            RunTestWithExpectedException(testMethodCase.ExpectedException, () => body(testContext));        else            body(testContext);    }    private static void RunTestWithExpectedException(Type expectedExceptionType, Action body)    {        try        {            body();        }        catch (Exception ex)        {            if (ex.GetType() == expectedExceptionType)                return;            throw;        }    }}
[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]public sealed class TestMethodCaseAttribute : Attribute{    public TestMethodCaseAttribute(params Object[] arguments)    {        this.Arguments = arguments;    }    public String Name { get; set; }    public Type ExpectedException { get; set; }    public Object[] Arguments { get; private set; }}
[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]public sealed class TestMethodCaseAttribute : Attribute{    public TestMethodCaseAttribute(params Object[] arguments)    {        this.Arguments = arguments;    }    public String Name { get; set; }    public Type ExpectedException { get; set; }    public Object[] Arguments { get; private set; }}
public class TestMethodCaseContext{    private readonly TestMethodCaseAttribute _testMethodCase;    internal TestMethodCaseContext(TestMethodCaseAttribute testMethodCase)    {        _testMethodCase = testMethodCase;    }    public T GetArgument<T>(Int32 index)    {        return (T)_testMethodCase.Arguments.ElementAtOrDefault(index);    }}
internal static class StackFrameHelper{    public static IEnumerable<StackFrame> GetCurrentCallStack()    {        var frameIndex = 0;        while (true)        {            var stackFrame = new StackFrame(frameIndex, false);            if (stackFrame.GetILOffset() == StackFrame.OFFSET_UNKNOWN)                break;            yield return stackFrame;            ++frameIndex;        }    }}

 

简易扩展Visual Studio UnitTesting支持TestMethodCase