Bug with --disable-mutation-types and --enable-mutation-types

Hi I have been testing out the new commands since they are quite useful. However I found some bugs related to them.

Here is a testProgram for mutation purpose

def testfunction(): 
    array['a'] = 123

I run this command after building v2.3 mutmut run --enable-mutation-types=number --paths-to-mutate testFunction.py followed by mutmut show all

and here is the output:

To apply a mutant on disk:
    mutmut apply <id>

To show a mutant:
    mutmut show <id>


Survived � (1)

---- testFunction.py (1) ----

# mutant 1
--- testFunction.py
+++ testFunction.py
@@ -1,3 +1,3 @@

 def testfunction():
-    array['a'] = 123
+    array['XXaXX'] = 123

This seems like a string mutation and not a number mutation, the correct number mutation after taking a brief look at the source code shoule be something like array['a'] = 124

You can get a similar “wrong” output when you run --disable-mutation-types=string

I am not very familar with the code base but I think this bug has something to do with overwriting mutations? see these lines https://github.com/boxed/mutmut/blob/cc7e7825a8a2ca0d5abb5f4748aa8c8ccea7f0f7/mutmut/__init__.py#L629-L643

[DudeNr33]

Oh, this is really a bug. Thanks @brutalsavage for being the beta tester for this! 😀

mutmut show shows a completely wrong mutant. Not only that it does not know about the enabled/disabled mutation types - it really shows the wrong mutant, not just one that was not run. In the given example, the only mutant which is performed and run is changing the number to 124. If we don’t have any tests for this, mutmut run will correctly report “1/1 SURVIVED”. But when you then run mutmut show all, it again lists only one surviving mutant, but this time it shows the mutant array["XXaXX"]. I have to dig deeper how the mutants are cached and identified later on.

Putting the value in the config at least does not help with the most recent version where I refactored to Click’s subcommands. I have to double check if this is different for V2.2.0.

[DudeNr33]

mutmut computes an array of possible mutations for each source code line. The cache stores the line and the index (that is: the index in the array of possible mutations):

class Mutant(db.Entity):
    line = Required(Line)
    index = Required(int)
    tested_against_hash = Optional(str, autostrip=False)
    status = Required(str, autostrip=False)  # really an enum of mutant_statuses

In my original implementation for --enable-mutation-types I returned too early from the mutate_node method and broke this indexing mechanism. With the linked PR mutmut now correctly identifies all possible mutations again, but simply does not perform a mutation if it does not belong to the desired mutation types.