add Stryker Mutator

[brodybits]

updated:

https://stryker-mutator.io/ - better than traditional code coverage (I think), as discussed in #60

shows the following summary at this point:

---------------|---------|----------|-----------|------------|----------|---------|
File           | % score | # killed | # timeout | # survived | # no cov | # error |
---------------|---------|----------|-----------|------------|----------|---------|
All files      |   59.53 |     1008 |       179 |        807 |        0 |       0 |
 dom-parser.js |   73.04 |      141 |         8 |         55 |        0 |       0 |
 dom.js        |   65.10 |      521 |        87 |        326 |        0 |       0 |
 entities.js   |    5.28 |        5 |         8 |        233 |        0 |       0 |
 sax.js        |   68.36 |      341 |        76 |        193 |        0 |       0 |
---------------|---------|----------|-----------|------------|----------|---------|

Seems to be OK in lib/dom-parser.js, pretty bad in lib/entities.js.

FUTURE TODO item:

• I would also like to integrate this with the Stryker dashboard, where it should be possible to scan a copy of the code for surviving mutants missing test coverage.

/cc @karfau

merging

I think these changes should be merged as a single squash commit upon final review.

[karfau]

In case you don't plan to commit the generated report you need to also ignore /reports. (At least this is a folder that was generated when I ran it earlier.)

[brodybits]

I just pushed some of the changes you had originally made for PR #51, which would probably overlap #73 now.

[brodybits]

Here is the badge from a fork I made, which links to the online report:

[karfau]

I'm very happy that the score is actually higher then when I first attempted it.
It means the way I converted the tests in the second go is more robust.

[brodybits]

I'm very happy that the score is actually higher then when I first attempted it.

That sure is nice progress, thanks!

FYI I did take the liberty to add newline to end of stryker.conf.json, which I think is standard editing practice and always done by vim.

[karfau]

Sure, I'm not sure why it wasn't there.
I never touched the file, so I guess this i the way that stryker generated it on init.