Guard against common Jest assertion testing shortcomings

jest-guard.js

// Unfortunately there's no global unhandledResolve handler :-(
process.on('unhandledRejection', error => {
  console.error('unhandledRejection', error);
  throw new Error('unhandledRejection' + error);
});

beforeEach(() => expect.hasAssertions());

sample.test.js

// Try running this with and without the following require:
require('./jest-guard')

test("I want this to fail, because I've forgotten to expect() anything", () => {});

test("I want this to fail because I haven't returned the expectation of a promise, and the assertion false", () => {
  expect(Promise.resolve(true)).resolves.toBe(false);
});

// Don't have a solution for these yet :-(
test("I want this to fail because I haven't returned the expectation of a promise even though the assertion passes", () => {
  expect(Promise.resolve(true)).resolves.toBe(true);
});

function neverResolveOrReject() {
  return new Promise((resolve, reject) => {});
}

test("I want this to fail because the promise never resolves or rejects - but it passes!!!", () => {
  expect(neverResolveOrReject()).resolves.toBe("something");
});