Migrated tests to jest

Used jest-codemods to migrate, will have to pass everything by hand before we can merge.

test3/initialize2DArray/initialize2DArray.js

@@ -0,0 +1,3 @@
+const initialize2DArray = (w, h, val = null) =>
+Array.from({ length: h }).map(() => Array.from({ length: w }).fill(val));
+module.exports = initialize2DArray;