Testing exceptions in unit test

NUnit has a nice feature (Assert.Throws) that makes it possible to assert that a exception is thrown inside some code.

Visual Studio Unit Testing Framework seem to miss this feature and to check that the correct exception is thrown you would could use the following code:

[TestMethod]
public void WithTryCatch()
{
    // Arrange
    ApplicationException actualException = null;

    // Act
    try
    {
        ThrowSomeException();
    }
    catch (ApplicationExceptionex)
    {
        actualException = ex;
    }

    // Assert
    Assert.IsNotNull(actualException);
    Assert.AreEqual("Message", actualException.Message);
}

ExpectedExceptionAttribute
Using the ExpectedExceptionAttribute is possible. In the example below you expect a exception of type ApplicationException with the message set to "ExceptionMessage". All derived exceptions from ApplicationException will also satisfy the test.

[TestMethod]
[ExpectedException(typeof(ApplicationException), "ExceptionMessage", true)]
public SomeTest()
{
    DoSomething();
}

ExceptionAssert
The ExpectedExceptionAttribute could be enough in many situations. But it will not make you able to test specific attributes on an exception or the value of its inner exception. So why not make things it a little easier and more flexible with a helper class.

[TestMethod]
public void WithHelperClass()
{
    // Arrange
    // Act
    // Assert
    ExceptionAssert.Throws<ApplicationException>(
        () => ThrowSomeException(),
        ex => Assert.AreEqual("Message", ex.Message));
}

The Throws method catches the exception specified and will run the asserts on it. If no (or wrong) exception is thrown the test will fail.

The source code for the helper class can be found below.

[DebuggerStepThrough]
public static class ExceptionAssert
{
 /// 

 /// Asserts that an exception of type T is not thrown
 /// 
 /// >Typeparam name="T">Exception to look for
 /// Action to execute
 public static void DoesNotThrow<T>(Action action) where T : Exception
 {
  if (action == null)
  {
   throw new ArgumentNullException("action");
  }

  Exception actualException = null;
  try
  {
   action();
  }
  catch (T ex)
  {
   actualException = ex;
  }

  if (actualException != null)
  {
   throw new AssertFailedException(String.Format(
    "ExceptionAssert.DoesNotThrow failed. Exception <{0}> thrown with message <{1}>",
    actualException.GetType().FullName,
    actualException.Message));
  }
 }

 /// 

 /// Asserts that an exception is not thrown
 /// 
 /// Action to execute
 public static void DoesNotThrow(Action action)
 {
  DoesNotThrow(action);
 }

 /// 

 /// Asserts that an exception of type T is thrown
 /// 
 /// Exception to look for
 /// Action to execute
 public static void Throws<T>(Action action) where T : Exception
 {
  if (action == null)
  {
   throw new ArgumentNullException("action");
  }

  Exception actualException = null;
  try
  {
   action();
  }
  catch (Exception ex)
  {
   actualException = ex;
  }

  ValidateThrownException<T>(actualException, null);
 }

 /// 

 /// Asserts that an exception of type T is thrown
 /// 
 /// Exception to look for
 /// Action to execute
 /// Additional assert to be made on the exception
 public static void Throws<T>(Action action, Action<T> asserts) where T : Exception
 {
  if (action == null)
  {
   throw new ArgumentNullException("action");
  }

  Exception actualException = null;
  try
  {
   action();
  }
  catch (Exception ex)
  {
   actualException = ex;
  }

  ValidateThrownException(actualException, asserts);
 }

 /// 

 /// Asserts that an exception of type T is thrown
 /// 
 /// Exception to look for
 /// Action to execute
 /// Additional assert to be made on the exception
 /// Cleanup action to be executed.
 public static void Throws<T>(Action action, Action<T> asserts, Action finalAction) where T : Exception
 {
  if (action == null)
  {
   throw new ArgumentNullException("action");
  }

  Exception actualException = null;
  try
  {
   action();
  }
  catch (Exception ex)
  {
   actualException = ex;
  }
  finally
  {
   if (finalAction != null)
   {
    finalAction();
   }
  }

  ValidateThrownException(actualException, asserts);
 }

 /// 

 /// Valdidates the exception
 /// 
 /// Exception type to look for
 /// Exception to validate
 /// Additional asserts to be made on the exception
 private static void ValidateThrownException<T>(Exception actualException, Action<T> asserts) where T : Exception
 {
  if (actualException is T)
  {
   if (asserts != null)
   {
    asserts(actualException as T);
   }
  }
  else if (actualException == null)
  {
   throw new AssertFailedException(String.Format(
    "ExceptionAssert.Throws failed. No exception was thrown. Expected <{0}>.",
    typeof(T).FullName));
  }
  else
  {
   throw new AssertFailedException(String.Format(
    "ExceptionAssert.Throws failed. Expected <{0}>. Actual <{1}>",
    typeof(T).FullName,
    actualException.GetType().FullName));
  }
 }
}

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ASP.NET LIVE: jQuery dialog extender for Asp.Net MVC Views

A good example of using the dialog in JQuery UI with ajax.

ASP.NET LIVE: jQuery dialog extender for Asp.Net MVC Views

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Variable number of arguments

The params keyword is very handy when you don't know the number of arguments is variable.
Note! No additional parameters are permitted after the params keyword.

// This method can take a variable number of ints
public int Sum(params int[] values)
{
  int sum = 0;
  foreach(int value in values)
  {
    sum += value;
  }
  return sum;
}

// Method calls
int sum1 = Sum(1, 2, 3, 4);
int sum2 = Sum(1, 2);

But be aware that this comes with a performance cost. When this method is called an array must be created, which is a costly operation.

If you know that your code for most of the time is calling this method with 3 arguments, then make a override with only three arguments. This method call is much quicker.

// Override with three params
public int Sum(int val1, int val2, int val3) { /* ... */ }

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AD LDS for Windows 7

On XP machines there was a a service called ADAM that could be used when you needed a lightweight ActiveDirectory. This was extremely useful when developing applications that used AD. You could test your application without the need to modify your client/company AD.

But this service was not supported in Vista or Win7.

But now Microsoft have released AD LDS for Win7 that can be downloaded here:

http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=a45059af-47a8-4c96-afe3-93dab7b5b658

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Comandline argument parser

Class that parses the commandline arguments.

using System;
using System.Collections.Generic;
using System.Text;
using System.Diagnostics;

namespace TestArgumentParser
{
    public class ArgumentParser
    {
        public string QuoteChars { get; set; }
        public string ValueSeparatorChars { get; set; }
        public string PrefixChars { get; set; }
        public Dictionary Params = new Dictionary();

        public string this[string key] { get{ return Params[key]; } }

        public ArgumentParser()
        {
            SetDefaultValues();
            string argString = GetComandLineArguments();
            Parse(argString);
        }

        public ArgumentParser(string args)
        {
            SetDefaultValues();
            Parse(args);
        }

        private static string GetComandLineArguments()
        {
            string argString = Environment.CommandLine;
            argString = argString.Replace("\"" + Process.GetCurrentProcess().MainModule.FileName + "\"", "");
            return argString;
        }

        public void Parse(string arguments)
        {
            string currentParam = string.Empty;
            string currentValue = string.Empty;
            bool readingParam = false;
            bool readingValue = false;
            bool startQuotes = false;
            foreach (char c in arguments)
            {
                if (IsPrefix(c))
                {
                    HandlePrefix(Params, ref currentParam, ref currentValue, ref readingParam);
                    continue;
                }
                if (readingParam)
                {
                    HandleParam(ref currentParam, ref readingParam, ref readingValue, c);
                    continue;
                }
                if (readingValue)
                {
                    HandleValue(ref currentValue, ref startQuotes, c);
                    continue;
                }

            }
            if (!string.IsNullOrEmpty(currentParam))
            {
                Params.Add(currentParam, currentValue);
            }
        }

        private void SetDefaultValues()
        {
            QuoteChars = "\"\'";
            ValueSeparatorChars = ":= ";
            PrefixChars = "-/";
        }

        private void HandlePrefix(Dictionary list, ref string currentParam, ref string currentValue, ref bool readingParam)
        {
            if (!string.IsNullOrEmpty(currentParam))
            {
                list.Add(currentParam, currentValue);
            }
            currentParam = string.Empty;
            currentValue = string.Empty;
            readingParam = true;
        }

        private void HandleValue(ref string currentValue, ref bool startQuotes, char c)
        {
            if (IsQuote(c))
            {
                startQuotes = !startQuotes;
                return;
            }
            if (!startQuotes && char.IsWhiteSpace(c))
            {
                return;
            }
            currentValue += c;
        }

        private void HandleParam(ref string currentParam, ref bool readingParam, ref bool readingValue, char c)
        {
            bool isValueSeparator = IsValueSeparator(c);
            if (!isValueSeparator)
            {
                currentParam += c;
            }
            else
            {
                readingValue = true;
                readingParam = false;
            }
        }

        private bool IsQuote(char c)
        {
            return QuoteChars.IndexOf(c) > -1;
        }

        private bool IsValueSeparator(char c)
        {
            return ValueSeparatorChars.IndexOf(c) > -1;
        }

        private bool IsPrefix(char c)
        {
            return PrefixChars.IndexOf(c) > -1;
        }
    }
}

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Expression trees

Howto get the name of a property or class. To minimize magic strings

Usage:

// This code will return "MyProperty".
ObjectHelper.GetMemberName(() => someEntity.MyProperty);

        using System;
using System.Linq.Expressions;
/// 
/// Extensions to object class
/// 
public static class ObjectHelper
{
/// 
/// Gets the name og the property og class using Expression trees
/// 
/// 
/// The expression to get name for
/// 
/// 
/// Type of the object
/// 
/// 
/// A string with the name, or an exception if it isn't a member expression
/// 
/// 
/// 
private static string GetMemberName(Expression> e)
{
var member = e.Body as MemberExpression;
// If the method gets a lambda expression
// that is not a member access,
// for example, () => x + y, an exception is thrown.
if (member == null)
{
throw new ArgumentException(
"'" + e +
"': is not a valid expression for this method");
}
return member.Member.Name;
}
}

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SMTP server for development purposes

Needed to test some code sending emails, but did not find the local SMTP sever on Windows 7.

Did a quick search and found this one.. sweet..

http://smtp4dev.codeplex.com/

Dummy SMTP server that sits in the system tray and does not deliver the received messages. The received messages can be quickly viewed, saved and the source/structure inspected. Useful for testing/debugging software that generates email.

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