Contains
Helper class with properties and methods that supply
            a number of constraints used in Asserts.
            
                
protected Contains()
Returns a new  SomeItemsConstraint checking for the
            presence of a particular object in the collection.
            
Returns a new DictionaryContainsKeyConstraint checking for the
            presence of a particular key in the dictionary.
            
Returns a constraint that succeeds if the actual
            value contains the substring supplied as an argument.
            
Returns a new DictionaryContainsValueConstraint checking for the
            presence of a particular value in the dictionary.