Test-Driven Python Development

Exploring assert methods

Now we have just one requirement for update remaining:

• -Done- It should take a timestamp and price value and set it on the object
• -Done- The price cannot be negative
• After multiple updates, the object gives us the latest price

Let us take the remaining requirement. Here is the test:

    def test_stock_price_should_give_the_latest_price(self):
        goog = Stock("GOOG")
        goog.update(datetime(2014, 2, 12), price=10)
        goog.update(datetime(2014, 2, 13), price=8.4)
        self.assertAlmostEqual(8.4, goog.price, delta=0.0001)

What this test does is to simply call update twice, and when we ask for the price, provide us with the newer one. The interesting point about the test is that we use the assertAlmostEqual method here. This method is often used ...