`mutations show <id>` results in `No mutation performed`

Thesis

Some mutations are marked as failed. However, they are not making any changes to the source code. And the tests are working. So, there’s an issue somewhere.

How to reproduce

Steps to reproduce (however, I am not sure that this can be reproduced with 100%):

1. Follow the installation steps of https://github.com/wemake-services/wemake-django-template
2. Install dependencies + install mutmut (it is not included)
3. Add this lines to the setup.cfg:

[mutmut]
paths_to_mutate = server/main_app
backup = False
runner = pytest
tests_dir = tests/

1. Run mutmut run

Related output

(.venv) ~/Desktop/test_project
» mutmut run

- Mutation testing starting -

These are the steps:
1. A full test suite run will be made to make sure we
   can run the tests successfully and we know how long
   it takes (to detect infinite loops for example)
2. Mutants will be generated and checked

Mutants are written to the cache in the .mutmut-cache
directory. Print found mutants with `mutmut results`.

Legend for output:
🎉 Killed mutants. The goal is for everything to end up in this bucket.
⏰ Timeout. Test suite took 10 times as long as the baseline so were killed.
🤔 Suspicious. Tests took a long time, but not long enough to be fatal.
🙁 Survived. This means your tests needs to be expanded.

1. Running tests without mutations
⠙ Running... Done

2. Checking mutants
⠦ 6/6  🎉 2  ⏰ 0  🤔 0  🙁 4

(.venv) ~/Desktop/test_project
» mutmut results
Timed out ⏰

Suspicious 🤔

Survived 🙁
mutmut apply 1
mutmut apply 2
mutmut apply 3
mutmut apply 4

(.venv) ~/Desktop/test_project
» mutmut show 1
No mutation performed

(.venv) ~/Desktop/test_project
» mutmut show 2
No mutation performed

(.venv) ~/Desktop/test_project
» mutmut show 3
--- server/main_app/urls.py
+++ server/main_app/urls.py
@@ -7,6 +7,6 @@
 # Place your URLs here:

 urlpatterns = [
-    url(r'^hello/$', index, name='hello'),
+    url(r'XX^hello/$XX', index, name='hello'),
 ]


(.venv) ~/Desktop/test_project
» mutmut show 4
--- server/main_app/urls.py
+++ server/main_app/urls.py
@@ -7,6 +7,6 @@
 # Place your URLs here:

 urlpatterns = [
-    url(r'^hello/$', index, name='hello'),
+    url(r'^hello/$', index, name='XXhelloXX'),
 ]

Originally posted as https://github.com/boxed/mutmut/issues/31#issuecomment-439907098

[boxed]

I just changed it to use sqlite for the database… I really disagree with the choices made in this cookiecutter template I must say. Super complex and python 3.6.6 specific (why so specific?), crazy amounts of dependencies, docker maybe?, coverage by default, explicit utf8 encoding markers on all files, but it’s python 3 so that’s the default anyway… it’s just a bit of a mess quite frankly.

In any case, after all that I can’t even reproduce the problem 😦

The config you specified seems a bit strange as you should only really need the paths_to_mutate setting, but even with it the same it give me the mutants fine:

>  mutmut show 1
--- server/main_app/apps.py
+++ server/main_app/apps.py
@@ -6,5 +6,5 @@
 class MainAppConfig(AppConfig):
     """Default django-app configuration."""
 
-    name = 'main_app'
+    name = 'XXmain_appXX'

etc

😦

[sobolevn]

Ok, I will update this issue if this happens once again. Thanks for all your efforts!

Closing this issue for now.

---

P.S. Super sad, that I did not like our template. Its main idea it to create super strict code quality and security checks for developers. So we can control quality of the project. And everything is turned on be default. And can not be switched off. Including coverage, all quality checks, etc, etc.

So we use the most specific instruments, patterns, and versions. coding: utf-8 saves a lot of time in some setups. There are different tools, terminal emulators, text editors, etc that still relies on it. We had a lot of problems with it. Explicit is better than implicit.