[ENHANCEMENT] Properly configure eslint to work with jest (#988)

* chore: make aware eslint that we use jest

By setting up the jest environment, we no longer need to declare the
'test' global in the configuration.

* chore: don't need to import expect, it's a jest environment global

* chore: don't need to import expect when creating undefined test

scripts/tdd.js

@@ -28,7 +28,6 @@ try {
   // Create files for undefined tests
   undefinedTests.forEach(snippet => {
     const exportTest = [
-      `const expect = require('expect');`,
       `const {${snippet}} = require('./_30s.js');`,
       `\ntest('${snippet} is a Function', () => {`,
       `  expect(${snippet}).toBeInstanceOf(Function);`,