Core util tests (#226)

* Error message formatting, deprecate unused functions
* Add 'test-coverage' script
* Additional test coverage for core util module
* Additional tests for core util module

by @mystery-house

package.json

@@ -6,6 +6,7 @@
   "scripts": {
     "test": "vitest run --version",
     "test-ui": "vitest --ui",
+    "test-coverage": "vitest --coverage",
     "bootstrap": "lerna bootstrap",
     "setup": "npm i && npm run bootstrap && cd repl && npm i && cd ../tutorial && npm i",
     "snapshot": "cd repl && npm run snapshot",
@@ -39,6 +40,7 @@
   "homepage": "https://strudel.tidalcycles.org",
   "devDependencies": {
     "@vitest/ui": "^0.21.1",
+    "c8": "^7.12.0",
     "events": "^3.3.0",
     "gh-pages": "^4.0.0",
     "happy-dom": "^6.0.4",