mstestは類似ユニットテストnunitにおけるastert.throws機能を実現する。

ユニットテストNUnitの中でAsssert.Throwsはとても使いやすいと言いますが、Ms Testを使う時はこのように書きます。

[TestMethod]
[ExpectedException(typeof(ArgumentNullException))]
public void WriteToTextFile()
{
PDFUtility.WriteToTextFile("D:\\ACA.pdf", null);
}

これからも拡張して、類似の成功エネルギーを実現して、一つのクラスを追加します。コードは以下の通りです。

/// <summary>
/// Useful assertions for actions that are expected to throw an exception.
/// </summary>
public static class ExceptionAssert
{
/// <summary>
/// Executes an exception, expecting an exception to be thrown.
/// Like Assert.Throws in NUnit.
/// </summary>
/// <param name="action">The action to execute</param>
/// <returns>The exception thrown by the action</returns>
public static Exception Throws(Action action)
{
return Throws(action, null);
}

/// <summary>
/// Executes an exception, expecting an exception to be thrown.
/// Like Assert.Throws in NUnit.
/// </summary>
/// <param name="action">The action to execute</param>
/// <param name="message">The error message if the expected exception is not thrown</param>
/// <returns>The exception thrown by the action</returns>
public static Exception Throws(Action action, string message)
{
try
{
action();
}
catch (Exception ex)
{
// The action method has thrown the expected exception.
// Return the exception, in case the unit test wants to perform further assertions on it.
return ex;
}

// If we end up here, the expected exception was not thrown. Fail!
throw new AssertFailedException(message ?? "Expected exception was not thrown.");
}

/// <summary>
/// Executes an exception, expecting an exception of a specific type to be thrown.
/// Like Assert.Throws in NUnit.
/// </summary>
/// <param name="action">The action to execute</param>
/// <returns>The exception thrown by the action</returns>
public static T Throws<T>(Action action) where T : Exception
{
return Throws<T>(action, null);
}

/// <summary>
/// Executes an exception, expecting an exception of a specific type to be thrown.
/// Like Assert.Throws in NUnit.
/// </summary>
/// <param name="action">The action to execute</param>
/// <param name="message">The error message if the expected exception is not thrown</param>
/// <returns>The exception thrown by the action</returns>
public static T Throws<T>(Action action, string message) where T : Exception
{
try
{
action();
}
catch (Exception ex)
{
T actual = ex as T;
if (actual == null)
{
throw new AssertFailedException(message ?? String.Format("Expected exception of type {0} not thrown. Actual exception type was {1}.", typeof(T), ex.GetType()));
}

// The action method has thrown the expected exception of type 'T'.
// Return the exception, in case the unit test wants to perform further assertions on it.
return actual;
}

// If we end up here, the expected exception of type 'T' was not thrown. Fail!
throw new AssertFailedException(message ?? String.Format("Expected exception of type {0} not thrown.", typeof(T)));
}
}

はい、今はMs Testの中でできます。下記のコードを見てください。