I am developing new functionality into a legacy coded application. However, for my new classes I have introduced Unit Testing. I still need to work with existing code.

One of the problems I face most is that a lot of partially static have been used.

Example of a class I need to use:

public class HelperClass
{
    public static bool ReturnSomething()
    {
        return true;
    }
}

My fix for making this testable:

public interface IHelperClass
{
    bool ReturnSomething();
}

public class HelperClass : IHelperClass
{
    public static bool ReturnSomething()
    {
        return true;
    }

    bool IHelperClass.ReturnSomething()
    {
        return ReturnSomething();
    }
}

A class that used to use the static, but by introducing a property (initialized by the constructor), that now uses the testable class. I can inject a mock using this property. Note that I could have used a factory for injecting the mock, however I wanted to keep it simple for the example.

public class UserClass
{
    public UserClass()
    {
        // Initialize with default 
        HelperClass = new HelperClass();
    }

    public IHelperClass HelperClass { get; set; }
}

My advantages:

• No need to modify existing code that is using the static class
• Code can be migrated from static to a testable instance by using
• I can reuse the existing concrete class

My disadvantages:

• Needed to modify legacy code that needs to be tested. Not always possible when in external assembly.
• PropertyName is the same as the class Name

I welcome any feedback to my suggested solution!

I am adding new functionality into a legacy application. For my new classes I have introduced Unit Testing. I still need to work with the existing code.

One of the problems I face is that a lot of static methods have been used.

Below is an example of a class I need to use:

public class HelperClass
{
    public static bool ReturnSomething()
    {
        return true;
    }
}

My fix for making this testable:

public interface IHelperClass
{
    bool ReturnSomething();
}

public class HelperClass : IHelperClass
{
    public static bool ReturnSomething()
    {
        return true;
    }

    bool IHelperClass.ReturnSomething()
    {
        return ReturnSomething();
    }
}

A class that used to use the static method, but by introducing a property (initialized by the constructor), that now uses the testable class. I can inject a mock using this property. Note that I could have used a factory for injecting the mock, however I wanted to keep it simple for the example.

public class UserClass
{
    public UserClass()
    {
        // Initialize with default 
        HelperClass = new HelperClass();
    }

    public IHelperClass HelperClass { get; set; }
}

My advantages:

• No need to modify existing code that is using the static class
• Code can be migrated from static to a testable instance
• I can reuse the existing concrete class

My disadvantages:

• Needed to modify legacy code that needs to be tested. Not always possible when in external assembly.
• PropertyName is the same as the class Name

I welcome any feedback!