Mocha support (server)

[simondel]

Server sided Mocha tests are not yet supported by stryker. See #11 for browser based Mocha test support.

[simondel]

Existing projects such as grunt-mocha-test can be used as reference.
The Mocha API can also be viewed in the Mocha source

[simondel]

We only copy the source files of a project to a different location to run the tests. This can cause issues when files are linked to each other using require statements that have relative paths. Since the test files are not copied, they will still require the original source files, instead of the copy.

[nicojs]

Wow! Nice find. This is indeed a problem.

The way i see it: we have 2 possibilities

1. Override the global require function. Then, if a require call is made, we forward it to the original require directly, unless it starts with . or .., in that case we rewire the require to the sand-boxed version of the file.
2. We just include the test files in the sandbox.

The second solution is safest but comes with a performance overhead.

The first solution is very error prone. For example:

1. As part of the unit test, the user can use something like Mockery or Rewire to override the global require themselves. This might not be a problem, but we'll have to test it anyway.
2. How do we distinguish between a require statement from the unit test framework and the production code. I might require something like '../../src/MySystemUnderTest' (clearly should be rewired to the sandbox version), but it could also be something like '../mocks/MockHelper' (clearly not to be rewired)
3. We also use require to make our code work. That one will also be the rewired one. We need to make sure this doesn't break anything.

I would go for the second solution for now, as it is safer. We can later change it if we want to optimize for performance.

[simondel]

https://github.com/stryker-mutator/stryker-mocha-runner