feat: Test running overhaul, switch to Prettier & reformat everything (#1407)

* chore: Switch to Node 20 + Vitest

* chore: migrate to vitest mock functions

* chore: code style (switch to prettier)

* test: re-enable long-running test

Seems the switch to Node 20 and Vitest has vastly improved the code's and / or the test's runtime!

see #1193

* chore: code style

* chore: fix failing tests

* Updated Documentation in README.md

* Update contribution guidelines to state usage of Prettier

* fix: set prettier printWidth back to 80

* chore: apply updated code style automatically

* fix: set prettier line endings to lf again

* chore: apply updated code style automatically

---------

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>

Cache/test/LFUCache.test.js

@@ -36,7 +36,8 @@ describe('Testing LFUCache class', () => {
       leastFrequency: 2
     })
 
-    const json = '{"misses":3,"hits":6,"cache":{"2":{"key":"2","value":2,"frequency":4},"4":{"key":"4","value":4,"frequency":2}}}'
+    const json =
+      '{"misses":3,"hits":6,"cache":{"2":{"key":"2","value":2,"frequency":4},"4":{"key":"4","value":4,"frequency":2}}}'
     expect(cache.toString()).toBe(json)
 
     const cacheInstance = cache.parse(json) // again merge the json
@@ -45,7 +46,8 @@ describe('Testing LFUCache class', () => {
 
     cache.capacity = 1 // decrease the capacity
 
-    expect(cache.info).toEqual({ // after merging the info
+    expect(cache.info).toEqual({
+      // after merging the info
       misses: 6,
       hits: 12,
       capacity: 1,

Cache/test/Memoize.test.js

@@ -43,11 +43,7 @@ describe('Testing Memoize', () => {
 
   it('expects the union function to use the cache on the second call', () => {
     const memoUnion = memoize(union)
-    const inputs = [
-      new Set([1, 2, 3]),
-      new Set([4, 3, 2]),
-      new Set([5, 3, 6])
-    ]
+    const inputs = [new Set([1, 2, 3]), new Set([4, 3, 2]), new Set([5, 3, 6])]
 
     expect(memoUnion(...inputs)).toEqual(new Set([1, 2, 3, 4, 5, 6]))
     expect(memoUnion(...inputs)).toEqual(union(...inputs))

Cache/test/cacheTest.js

@@ -31,7 +31,5 @@ export const fibonacciCache = (n, cache = null) => {
  * @return {new Set}
  */
 export const union = (...sets) => {
-  return new Set(
-    sets.reduce((flatArray, set) => [...flatArray, ...set], [])
-  )
+  return new Set(sets.reduce((flatArray, set) => [...flatArray, ...set], []))
 }