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https://github.com/mutpy/mutpy

MutPy is a mutation testing tool for Python 3.x source code
https://github.com/mutpy/mutpy

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MutPy is a mutation testing tool for Python 3.x source code

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MutPy

=====



|Python Versions| |Build Status| |Coverage Status| |Code Climate|



MutPy is a mutation testing tool for Python 3.3+ source code. MutPy

supports standard unittest module, generates YAML/HTML reports and has

colorful output. It applies mutation on AST level. You could boost your

mutation testing process with high order mutations (HOM) and code

coverage analysis.



Mutation testing

----------------



From article at Wikipedia:



    **Mutation testing** (or Mutation analysis or Program mutation)

    evaluates the quality of software tests. Mutation testing involves

    modifying a program's source code or byte code in small ways. A test

    suite that does not detect and reject the mutated code is considered

    defective. These so-called mutations, are based on well-defined

    mutation operators that either mimic typical programming errors

    (such as using the wrong operator or variable name) or force the

    creation of valuable tests (such as driving each expression to

    zero). The purpose is to help the tester develop effective tests or

    locate weaknesses in the test data used for the program or in

    sections of the code that are seldom or never accessed during

    execution.



Installation

------------



You can easily install MutPy from PyPi:



::



    $ pip install mutpy



... or if you want to have latest changes you can clone this repository

and install MutPy from sources:



::



    $ git clone [email protected]:mutpy/mutpy.git

    $ cd mutpy/

    $ python3 setup.py install



Example

-------



Main code (``calculator.py``) - we will mutate it:



.. code:: python



    def mul(x, y):

        return x * y



Test (``test_calculator.py``) - we will check its quality:



.. code:: python



    from unittest import TestCase

    from calculator import mul



    class CalculatorTest(TestCase):



        def test_mul(self):

            self.assertEqual(mul(2, 2), 4)



Now we can run MutPy in the same directory where we have our sources

files:



::



    $ mut.py --target calculator --unit-test test_calculator -m



This command will produce the following output:



::



    [*] Start mutation process:

       - targets: calculator

       - tests: test_calculator

    [*] All tests passed:

       - test_calculator [0.00031 s]

    [*] Start mutants generation and execution:

       - [#   1] AOR calculator.py:2  :

    --------------------------------------------------------------------------------

     1: def mul(x, y):

    ~2:     return x / y

    --------------------------------------------------------------------------------

    [0.02944 s] killed by test_mul (test_calculator.CalculatorTest)

       - [#   2] AOR calculator.py:2  :

    --------------------------------------------------------------------------------

     1: def mul(x, y):

    ~2:     return x // y

    --------------------------------------------------------------------------------

    [0.02073 s] killed by test_mul (test_calculator.CalculatorTest)

       - [#   3] AOR calculator.py:2  :

    --------------------------------------------------------------------------------

     1: def mul(x, y):

    ~2:     return x ** y

    --------------------------------------------------------------------------------

    [0.01152 s] survived

       - [#   4] SDL calculator.py:2  :

    --------------------------------------------------------------------------------

     1: def mul(x, y):

    ~2:     pass

    --------------------------------------------------------------------------------

    [0.01437 s] killed by test_mul (test_calculator.CalculatorTest)

    [*] Mutation score [0.21818 s]: 75.0%

       - all: 4

       - killed: 3 (75.0%)

       - survived: 1 (25.0%)

       - incompetent: 0 (0.0%)

       - timeout: 0 (0.0%)



First of all we run MutPy with few parameters. The most important are:



-  ``--target`` - after this flag we should pass module which we want to

   mutate.

-  ``--unit-test`` - this flag point to our unit tests module.



There are few phases in mutation process which we can see on printed by

MutPy output (marked by star ``[*]``):



-  main code and tests modules loading,

-  run tests with original (not mutated) code base,

-  code mutation (main mutation phase),

-  results summary.



There are 4 mutants generated in main mutation phase - 3 of them are

killed and only 1 mutant survived. We can see all stats at the end of

MutPy output. In this case MutPy didn't generate any incompetent (raised

``TypeError``) and timeout (generated infinite loop) mutants. Our

mutation score (killed to all mutants ratio) is 75%.



To increase mutation score (100% is our target) we need to improve our

tests. This is a mutant which survived:



.. code:: python



    def mul(x, y):

        return x ** y



This mutant survived because our test check if ``2 * 2 == 4``. Also

``2 ** 2 == 4``, so this data aren't good to specify multiplication

operation. We should change it, eg:



.. code:: python



    from unittest import TestCase

    from calculator import mul



    class CalculatorTest(TestCase):



        def test_mul(self):

            self.assertEqual(mul(2, 3), 6)



We can run MutPy again and now mutation score is equal 100%.



Command-line arguments

----------------------



List of all arguments with which you can run MutPy:



-  ``-t TARGET [TARGET ...]``, ``--target TARGET [TARGET ...]`` - target

   module or package to mutate,

-  ``-u UNIT_TEST [UNIT_TEST ...]``,

   ``--unit-test UNIT_TEST [UNIT_TEST ...]`` - test class, test method,

   module or package with unit tests,

-  ``--runner RUNNER`` - currently supported are: unittest (default), pytest (experimental)

-  ``-m``, ``--show-mutants`` - show mutants source code,

-  ``-r REPORT_FILE``, ``--report REPORT_FILE`` - generate YAML report,

-  ``--report-html DIR_NAME`` - generate HTML report,

-  ``-f TIMEOUT_FACTOR``. ``--timeout-factor TIMEOUT_FACTOR`` - max

   timeout factor (default 5),

-  ``-d``, ``--disable-stdout`` - try disable stdout during mutation

   (this option can damage your tests if you interact with

   ``sys.stdout``),

-  ``-e``. ``--experimental-operators`` - use experimental operators,

-  ``-o OPERATOR [OPERATOR ...]``,

   ``--operator OPERATOR [OPERATOR ...]`` - use only selected operators,

-  ``--disable-operator OPERATOR [OPERATOR ...]`` - disable selected

   operators,

-  ``-l``. ``--list-operators`` - list available operators,

-  ``-p DIR``. ``--path DIR`` - extend Python path,

-  ``--percentage PERCENTAGE`` - percentage of the generated mutants

   (mutation sampling),

-  ``--coverage`` - mutate only covered code,

-  ``-h``, ``--help`` - show this help message and exit,

-  ``-v``, ``--version`` - show program's version number and exit,

-  ``-q``, ``--quiet`` - quiet mode,

-  ``--debug`` - debug mode,

-  ``-c``. ``--colored-output`` - try print colored output,

-  ``--order ORDER`` - mutation order,

-  ``--hom-strategy HOM_STRATEGY`` - HOM strategy,

-  ``--list-hom-strategies`` - list available HOM strategies,

-  ``--mutation-number MUTATION_NUMBER`` - run only one mutation (debug

   purpose).



Mutation operators

------------------



List of MutPy mutation operators sorted by alphabetical order:



-  AOD - arithmetic operator deletion

-  AOR - arithmetic operator replacement

-  ASR - assignment operator replacement

-  BCR - break continue replacement

-  COD - conditional operator deletion

-  COI - conditional operator insertion

-  CRP - constant replacement

-  DDL - decorator deletion

-  EHD - exception handler deletion

-  EXS - exception swallowing

-  IHD - hiding variable deletion

-  IOD - overriding method deletion

-  IOP - overridden method calling position change

-  LCR - logical connector replacement

-  LOD - logical operator deletion

-  LOR - logical operator replacement

-  ROR - relational operator replacement

-  SCD - super calling deletion

-  SCI - super calling insert

-  SIR - slice index remove



Experimental mutation operators:



-  CDI - classmethod decorator insertion

-  OIL - one iteration loop

-  RIL - reverse iteration loop

-  SDI - staticmethod decorator insertion

-  SDL - statement deletion

-  SVD - self variable deletion

-  ZIL - zero iteration loop



Supported Test Runners

----------------------



Currently the following test runners are supported by MutPy:



- `unittest `_

- `pytest `_



License

-------



Licensed under the Apache License, Version 2.0. See LICENSE file.



MutPy was developed as part of engineer's and master’s thesis at

Institute of Computer Science, Faculty of Electronics and Information

Technology, Warsaw University of Technology.



.. |Python Versions| image:: https://img.shields.io/pypi/pyversions/MutPy.svg

   :target: https://github.com/mutpy/mutpy

.. |Build Status| image:: https://travis-ci.org/mutpy/mutpy.svg?branch=master

   :target: https://travis-ci.org/mutpy/mutpy

.. |Coverage Status| image:: https://coveralls.io/repos/github/mutpy/mutpy/badge.svg?branch=master

   :target: https://coveralls.io/github/mutpy/mutpy?branch=master

.. |Code Climate| image:: https://codeclimate.com/github/mutpy/mutpy/badges/gpa.svg

   :target: https://codeclimate.com/github/mutpy/mutpy