Improve unit test usability (#2463)

The unit tests were a little tricky to work with, for failures the
wrong line numbers were given and console.log() didn't work. Let's try
to improve the situation:

1. Have the unit tests bundled with inline sourcemaps, that can then
   be used to report the line numbers correctly.
2. Add a note to the unit test's README to mention to use
   console.warn() or console.error() instead of console.log().

Note: Unfortunately adding inline sourcemaps seems to slow down
      Karma/Jasmine quite a bit. In the future, we might consider
      using a faster test runner, or one that supports external
      sourcemaps.

Makefile

@@ -67,7 +67,7 @@ watch:
 ## unit-test: Run the unit tests.
 ESBUILD_TESTS = unit-test/background/*.js unit-test/background/**/*.js unit-test/ui/**/*.js unit-test/shared-utils/*.js
 unit-test:
-	$(ESBUILD) --outdir=build/test --inject:./unit-test/inject-chrome-shim.js $(ESBUILD_TESTS)
+	$(ESBUILD) --sourcemap=inline --outdir=build/test --inject:./unit-test/inject-chrome-shim.js $(ESBUILD_TESTS)
 	node_modules/.bin/karma start karma.conf.js
 
 .PHONY: unit-test

unit-test/README.md

@@ -12,3 +12,10 @@ Tests can be run as follows:
  - `npm test`: Run all tests (both node and browser).
  - `npm run test.unit`: Run only browser-based unit tests.
  - `npm run test.node`: Run only node-based unit tests.
+
+## Notes
+
+- To reduce the amount of noise when running the tests, `console.log()` and
+  `console.debug()` output is suppressed. If you need to log something to the
+  console while working on the tests use `console.warn()` or `console.error()`
+  instead.