[c#] Assert로 예외를 테스트하여 예외가 발생하는지 확인하는 가장 좋은 방법

ExpectedException애트리뷰트 를 사용하는 대신 테스트 클래스에 유용한 두 가지 방법을 정의하는 경우가 있습니다.

AssertThrowsException() 대리자를 취하고 예상 된 메시지와 함께 예상되는 예외를 throw한다고 주장합니다.

AssertDoesNotThrowException() 동일한 대리자를 취하고 예외가 발생하지 않는다고 주장합니다.

이 쌍은 예외가 한 경우에 발생하지만 다른 경우에는 발생하지 않는지 테스트하려는 경우 매우 유용 할 수 있습니다.

내 단위 테스트 코드를 사용하면 다음과 같습니다.

ExceptionThrower callStartOp = delegate(){ testObj.StartOperation(); };

// Check exception is thrown correctly...
AssertThrowsException(callStartOp, typeof(InvalidOperationException), "StartOperation() called when not ready.");

testObj.Ready = true;

// Check exception is now not thrown...
AssertDoesNotThrowException(callStartOp);

멋지고 깔끔한 응?

My AssertThrowsException()및 AssertDoesNotThrowException()메서드는 다음과 같이 공통 기본 클래스에 정의됩니다.

protected delegate void ExceptionThrower();

/// <summary>
/// Asserts that calling a method results in an exception of the stated type with the stated message.
/// </summary>
/// <param name="exceptionThrowingFunc">Delegate that calls the method to be tested.</param>
/// <param name="expectedExceptionType">The expected type of the exception, e.g. typeof(FormatException).</param>
/// <param name="expectedExceptionMessage">The expected exception message (or fragment of the whole message)</param>
protected void AssertThrowsException(ExceptionThrower exceptionThrowingFunc, Type expectedExceptionType, string expectedExceptionMessage)
{
    try
    {
        exceptionThrowingFunc();
        Assert.Fail("Call did not raise any exception, but one was expected.");
    }
    catch (NUnit.Framework.AssertionException)
    {
        // Ignore and rethrow NUnit exception
        throw;
    }
    catch (Exception ex)
    {
        Assert.IsInstanceOfType(expectedExceptionType, ex, "Exception raised was not the expected type.");
        Assert.IsTrue(ex.Message.Contains(expectedExceptionMessage), "Exception raised did not contain expected message. Expected=\"" + expectedExceptionMessage + "\", got \"" + ex.Message + "\"");
    }
}

/// <summary>
/// Asserts that calling a method does not throw an exception.
/// </summary>
/// <remarks>
/// This is typically only used in conjunction with <see cref="AssertThrowsException"/>. (e.g. once you have tested that an ExceptionThrower
/// method throws an exception then your test may fix the cause of the exception and then call this to make sure it is now fixed).
/// </remarks>
/// <param name="exceptionThrowingFunc">Delegate that calls the method to be tested.</param>
protected void AssertDoesNotThrowException(ExceptionThrower exceptionThrowingFunc)
{
    try
    {
        exceptionThrowingFunc();
    }
    catch (NUnit.Framework.AssertionException)
    {
        // Ignore and rethrow any NUnit exception
        throw;
    }
    catch (Exception ex)
    {
        Assert.Fail("Call raised an unexpected exception: " + ex.Message);
    }
}