diff --git a/src/www/js/jest/__tests__/async.solution.spec.js b/src/www/js/jest/__tests__/async.solution.spec.js
new file mode 100644
index 0000000..e63da89
--- /dev/null
+++ b/src/www/js/jest/__tests__/async.solution.spec.js
@@ -0,0 +1,77 @@
+const { find, propEq } = require('ramda')
+
+const todos = [
+  { id: 1, text: 'Learn Jest' },
+  { id: 2, text: 'Learn async' },
+  { id: 3, text: '???' },
+  { id: 4, text: 'Profit 💸' },
+]
+
+const getTodos = () => (
+  new Promise((res) => {
+    process.nextTick(() => {
+      res(todos)
+    })
+  })
+)
+
+const getTodo = async (id) => {
+  const todos = await getTodos()
+  const todo = find(propEq('id', id), todos)
+
+  if (!todo) throw new Error(`Todo ID ${id} not found`)
+  // if (!todo) return Promise.reject(`Todo ID ${id} not found`)
+
+  return todo
+}
+
+const getTodoInBackground = (id, cb) => {
+  getTodos()
+    .then((todos) => cb(find(propEq('id', id), todos)))
+  return true
+}
+
+describe('Async tests', () => {
+  describe('#getTodos', () => {
+    it('should work with async/await', async () => {
+      const res = await getTodos()
+      expect(res).toEqual(todos)
+    })
+
+    it('should work with await + resolves', async () => {
+      await expect(getTodos()).resolves.toEqual(todos)
+    })
+
+    it('should work by returning a promise', () => {
+      return getTodos()
+        .then((res) => {
+          expect(res).toEqual(todos)
+        })
+    })
+  })
+
+  describe('#getTodo', () => {
+    it('should find a todo', async () => {
+      await expect(getTodo(1)).resolves.toEqual(todos[0])
+    })
+
+    it('should throw error when todo not found', async () => {
+      return await expect(getTodo(42)).rejects.toThrow('Todo ID 42 not found')
+    })
+
+    // TODO what's wrong with this test?
+    it('should throw an error for missing todo', async () => {
+      await expect(getTodo(42)).rejects.toThrow('Todo ID 42 not found')
+    })
+  })
+
+  describe('#getTodoInBackground', () => {
+    it('should get a todo in background and pass to callback', async () => {
+      const flushPromises = () => new Promise(process.nextTick)
+      const mock = jest.fn()
+      getTodoInBackground(1, mock)
+      await flushPromises()
+      expect(mock).toHaveBeenCalledWith(todos[0])
+    })
+  })
+})
diff --git a/src/www/js/jest/__tests__/async.spec.js b/src/www/js/jest/__tests__/async.spec.js
index b01917a..ab48c8c 100644
--- a/src/www/js/jest/__tests__/async.spec.js
+++ b/src/www/js/jest/__tests__/async.spec.js
@@ -20,14 +20,13 @@ const getTodo = async (id) => {
   const todo = find(propEq('id', id), todos)
 
   if (!todo) throw new Error(`Todo ID ${id} not found`)
-  // if (!todo) return Promise.reject(`Todo ID ${id} not found`)
 
   return todo
 }
 
 const getTodoInBackground = (id, cb) => {
   getTodos()
-    .then((todos) => find(propEq('id', id), todos))
+    .then((todos) => cb(find(propEq('id', id), todos)))
   return true
 }
 
@@ -43,13 +42,9 @@ describe('Async tests', () => {
   describe('#getTodo', () => {
     it.todo('should find a todo')
 
-    // it.todo('should throw error when todo not found')
-    it('should throw error when todo not found', async () => {
-      return await expect(getTodo(42))
-        .rejects.toThrow('Todo ID 42 not found')
-    })
+    it.todo('should throw error when todo not found')
 
-    // TODO what's wrong with this test?
+    // TODO what's wrong with this test? Rewrite it so it doesn't silently fail
     it('should throw an error for missing todo', async () => {
       try {
         await getTodo(1)
diff --git a/src/www/js/jest_mocks/__tests__/coin.solution.test.js b/src/www/js/jest_mocks/__tests__/coin.solution.test.js
new file mode 100644
index 0000000..f406b62
--- /dev/null
+++ b/src/www/js/jest_mocks/__tests__/coin.solution.test.js
@@ -0,0 +1,39 @@
+import { coinFlip, winJackpot } from '../coin'
+import { getRandomInt } from '../random'
+import { resetJackpot } from '../store'
+
+jest.mock('../random')
+
+describe('#coinFlip', () => {
+  it('should return Heads or Tails based on random generator', () => {
+    /**
+     * TODO these will fail randomly. Use `jest.mock` to control the output
+     *      of the random number generator and test the coin flip behavior.
+     *      You should not have to change the implementation files.
+     */
+    getRandomInt.mockReturnValueOnce(true)
+    expect(coinFlip()).toEqual('Heads')
+    getRandomInt.mockReturnValueOnce(false)
+    expect(coinFlip()).toEqual('Tails')
+  })
+})
+
+jest.mock('../store', () => ({
+  getCurrentJackpot: jest.fn().mockReturnValue(100),
+  resetJackpot: jest.fn()
+}))
+
+describe('#winJackpot', () => {
+  it('should reset the jackpot and return the winnings message', () => {
+    /**
+     * TODO
+     *   Using an inline mock `jest.mock('./dep', () => { ... }) to mock
+     *   the behavior of the store.
+     *   1. Test that a message of "You won $...!" is returned based off
+     *      the current jackpot.
+     *   2. Test that the jackpot is told to reset.
+     */
+    expect(winJackpot()).toEqual('You won $100!')
+    expect(resetJackpot).toHaveBeenCalled()
+  })
+})