Mocha overrides

[adelespinasse]

The overrides file for Mocha includes

    "diff": "@empty",

which I think is probably why it behaves strangely when a test fails:

err  TypeError: diff.createPatch is not a function
    at unifiedDiff (file:///C:/Users/aldel/agora/playdoh/public/jspm_packages/npm/[email protected]/lib/reporters/base.js:417:18)
    at file:///C:/Users/aldel/agora/playdoh/public/jspm_packages/npm/[email protected]/lib/reporters/base.js:218:16
...

Mocha is trying to use diff to format its output for the failure (I assume), but diff is empty because of the override. Is this override needed for something?

[adelespinasse]

I got it to behave correctly by removing the override (directly editing the override in my package.json) and installing diff with jspm install --dev npm:diff. No idea why that override exists.

I don't have enough confidence about jspm configuration to submit a pull request.

[aluanhaddad]

See also #1022.

[adelespinasse]

Oh, I later noticed that this is a problem with the exceptions thrown by Chai, but not by Unexpected, and not if the test simply does something like throw new Error('error'). Possibly this is why @guybedford didn't notice the issue when writing the Mocha overrides and/or this article. I guess Mocha has special handling for Chai's exceptions.

[aluanhaddad]

Honestly I know little about test frameworks such as mocha, chai, and sinon. Instead I use tape + jspm run test/index whenever I can because I like for to test frameworks to be simple and I dislike when they encourage mutating steps.

Thanks for linking that article here, it is indeed a great read and was a pleasure to read again.