Refactoring tests

With the first test passing, we can go ahead with the second test:

    def test_increasing_trend_is_false_if_price_decreases(self):
        timestamps = [datetime(2014, 2, 11), datetime(2014, 2, 12), \ 
            datetime(2014, 2, 13)]
        prices = [8, 12, 10]
        for timestamp, price in zip(timestamps, prices):
            self.goog.update(timestamp, price)
        self.assertFalse(self.goog.is_increasing_trend())

Our implementation already passes this test, so let us move on to the third test:

    def test_increasing_trend_is_false_if_price_equal(self):
        timestamps = [datetime(2014, 2, 11), datetime(2014, 2, 12), \ 
            datetime(2014, 2, 13)]
        prices = [8, 10, 10]
        for timestamp, price in zip(timestamps, prices):
            self.goog.update(timestamp, price)
        self.assertFalse(self.goog.is_increasing_trend())

The current code passes this test as well. But let us pause at this point. If we look at the test cases so far, we can...