>>>I have updated my answer
>>
>>I have a compiler warning (green underline) under this test
>>
>>

>> public static Int32 Occurs(this String source, char pattern)
>>      {
>>         if (null==pattern)
>>            return 0;
>>         return source.Split(pattern).Length - 1;
>>      }

>>
>>It is saying that value of type int never equals null.
>>
>>So, do I really need this test here for char?
>
>Value types are never null - unless declared as nullable

So, I do not need a test above.

BTW, now I am facing a really weird situation. Yesterday I ran the tests, all was well. Today I am getting this error about the method not found :(

I re-added the references in all 3 projects in the solution and now it passes again. Weird.