Included Mutators

Muzak includes only three mutators - Constants.Numbers, Constants.Strings and Functions.Rename. While this is indeed rather limited, it should give some examples of the benefits of mutation testing.

Constants.Numbers

Mutates any Integer or Float literals.

Original File

def do_math(num), do: num + 2 - 0.38

Generated mutations

def do_math(num), do: num + 327_237_729 - 0.38

def do_math(num), do: num + 2 - 392_763.216_279

Constants.Strings

Mutates any string literals.

Original File

def append(str), do: str <> " added on " <> " a string."

Generated mutations

def append(str), do: str <> "random_string" <> " a string."

def append(str), do: str <> " added on " <> "random_string"

Functions.Rename

Renames any function or macro definition.

Original File

def add_one(int), do: do_add_one(int)

defp do_add_one(int), do: int + 1

Generated mutations

def random_function_name(int), do: do_add_one(int)

defp do_add_one(int), do: int + 1

def add_one(int), do: do_add_one(int)

defp random_function_name(int), do: int + 1