Shopping lab errors

1) #viewCart should print each item in the cart and their cost:
     Error: spy was never called with [ 'In your cart, you have socks at $undefined, puppy at $undefined, iPhone at $undefined.' ]
      at assert (node_modules/expect/lib/assert.js:29:9)
      at Expectation.toHaveBeenCalledWith (node_modules/expect/lib/Expectation.js:333:28)
      at Context.<anonymous> (test/index-test.js:44:25)

  2) #total adds up the prices of the items in the cart:

      Error: Expected 100 to equal NaN
      + expected - actual

      -100
      +NaN

      at assert (node_modules/expect/lib/assert.js:29:9)
      at Expectation.toEqual (node_modules/expect/lib/Expectation.js:81:30)
      at Context.<anonymous> (test/index-test.js:68:21)

  3) #removeFromCart removes the item from the cart:
     Error: Expected false to be true
      at assert (node_modules/expect/lib/assert.js:29:9)
      at Expectation.toBe (node_modules/expect/lib/Expectation.js:66:28)
      at Context.<anonymous> (test/index-test.js:76:41)