Basic runner implementation

[jankuca]

I implemented a very naive runner which executes npm test -- file file file. Jest does not provide a simple programmatic API with which we can work and this works fine.

All the projects using this runner must do is to have a test script in package.json which runs jest.

[simondel]

Thanks for this PR! We'll take a look at it.

As of right now, we have a couple of questions:

• Why did you remove files such as the .bithoundrc and .travis.yml?
• Is this a work in progress or is this done?
• How well does this perform? Spawning a new process for every mutant can be quite slow when you have a couple thousand mutants.

[nicojs]

I see what you did there @jankuca . Its a neat idea. Could you also do this by calling the jest CLI directly? Instead of relying on npm test? Seems pretty straight forward.

As @simondel mentioned, this way of working has as disadvantage that it is slow (spawning a new process per call). I would not like to support it myself, i would rather try to get the Jest maintainers to create a public API for us to use, or we use there private API (if it is somewhat stable).

However, until then, would you agree to create a fork and release it under a different name (for example: stryker-jest-cli-runner)? That way, people can already start using stryker with jest. We can than also add it to the official documentation and refer to your repo for the details.

[nicojs]

@jankuca we just released a version of a basic jest test runner. Can you test to see if it works for you?

[jankuca]

That's great! But it does not seem to work for me, no idea why.

Mutants are created but none fail. My npm test script is simply jest which runs tests and fails when I manually apply a mutant myself.

69 total mutants.
69 mutants survived.
  of which 69 were not covered by the tests.
0 mutants timed out.
0 mutants killed.
Ran 0.00 tests per mutant on average.
Mutation score based on covered code: n/a
Mutation score based on all code: 0.00%

My stryker.conf.js file:

module.exports = function (config) {
  config.set({
    files: [
      { pattern: 'src/**/!(*.spec).js', included: false, mutated: true },
      { pattern: 'src/**/*.spec.js', included: true, mutated: false },
    ],
    testRunner: 'jest-test-runner',
    coverageAnalysis: 'off',
    reporter: [ 'clear-text', 'progress' ],
  });
}

[mthmulders]

@jankuca Could you please open a separate issue for that? Seems worth investigating. Also, could you please include trace logging?

[nicojs]

@mthmulders @jankuca i've created #11 for this purpose