Add Jest test runner with 20% coverage minimum

[akprasad]

To make our JavaScript code more robust, switch to CLI-based testing that runs as part of our usual deploys.

Test plan: ran the tests.

[epicfaace]

You might be able to use ts-jest; it looks like ts-jest recently added support for esbuild as an experimental feature. Though I'm not clear if this support is working yet. See:

• https://kulshekhar.github.io/ts-jest/docs/guides/esm-support#use-esm-presets
• https://github.com/kulshekhar/ts-jest/search?q=esbuild
• Support for esbuild or swc kulshekhar/ts-jest#2135

[Smrtnyk]

ts-jest does not support esbuild based transpilation
you could use swc-jest, we use at the company to run around 5k tests and it is pretty fast and awesome

[epicfaace]

@akprasad what did you mean by "Jest thinks everything being tested is one big file"? Can you send the coverage output you get (or perhaps change CI to print out coverage output to the console, instead of writing it out to a file)?

[epicfaace]

@akprasad what did you mean by "Jest thinks everything being tested is one big file"? Can you send the coverage output you get (or perhaps change CI to print out coverage output to the console, instead of writing it out to a file)?

[akprasad]

@akprasad what did you mean by "Jest thinks everything being tested is one big file"? Can you send the coverage output you get (or perhaps change CI to print out coverage output to the console, instead of writing it out to a file)?

I mean that Jest doesn't distinguish among different source files. The output has changed a little bit since I wrote that, but here's what we get now:

 PASS  test/js/reader.test.js
 PASS  test/js/dictionary.test.js
 PASS  test/js/proofer.test.js
 PASS  test/js/routes.test.js
----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
----------|---------|----------|---------|---------|-------------------
All files |       0 |        0 |       0 |       0 |
----------|---------|----------|---------|---------|-------------------

with no indication of either total coverage or coverage per source file.

[akprasad]

I'm switching to Babel to unblock this. Tracking the esbuild work in #212.