Migrated tests to jest

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

test/observeMutations/observeMutations.js

@@ -1,19 +0,0 @@
-const observeMutations = (element, callback, options) => {
-const observer = new MutationObserver(mutations => mutations.forEach(m => callback(m)));
-observer.observe(
-element,
-Object.assign(
-{
-childList: true,
-attributes: true,
-attributeOldValue: true,
-characterData: true,
-characterDataOldValue: true,
-subtree: true
-},
-options
-)
-);
-return observer;
-};
-module.exports = observeMutations;