chore(tests): Use node env for Jest to avoid JSDOM overhead

[okonet]

What kind of change does this PR introduce?
build related change

Did you add tests for your changes?

Not relevant

If relevant, did you update the documentation?

Not relevant

Summary

Jest can be configured to run in Node env only without emulating browser with JSDOM: https://facebook.github.io/jest/docs/en/configuration.html#testenvironment-string

This improves tests running speed significantly:

Before

Test Suites: 31 passed, 31 total
Tests:       1 skipped, 126 passed, 127 total
Snapshots:   110 passed, 110 total
Time:        24.577s

After

Test Suites: 31 passed, 31 total
Tests:       1 skipped, 126 passed, 127 total
Snapshots:   110 passed, 110 total
Time:        15.168s, estimated 19s

[cpojer]

I don't think this is correct. switching from jsdom to node will improve Jest's startup time by about 400ms but it should be a one time cost. Based on your output, it seems like the second run was using a cache but the first one wasn't (as indicated by "estimated xx seconds").

Can you try:

• Run Jest once with either environment.
• Run Jest again, this time it will use the cache.
• Switch the environment, it will keep using the cache.

And then compare timings for #2 and #3?

[okonet]

@cpojer thanks for looking at it. Here are my timings:

Second run with node env:

Time:        17.528s

Switching back to defaults:

Time:        22.979s

Second run defaults:

Time:        17.542s

So it seems you're right about the caching.

[cpojer]

Still worth doing, as you are running this code in a node environment.