Test-Driven Development with Python

Chapter 13. Dipping Our Toes, Very Tentatively, into JavaScript

If the Good Lord had wanted us to enjoy ourselves, he wouldn’t have granted us his precious gift of relentless misery.

— John Calvin (as portrayed in Calvin and the Chipmunks)

Our new validation logic is good, but wouldn’t it be nice if the error messages disappeared once the user started fixing the problem? For that we’d need a teeny-tiny bit of JavaScript.

We are utterly spoiled by programming every day in such a joyful language as Python. JavaScript is our punishment. So let’s dip our toes in, very gingerly.

Warning

I’m going to assume you know the basics of JavaScript syntax. If you haven’t read JavaScript: The Good Parts, go and get yourself a copy right away! It’s not a very long book.

Starting with an FT

Let’s add a new functional test to the ItemValidationTest class:

functional_tests/test_list_item_validation.py (ch14l001). 

def test_error_messages_are_cleared_on_input(self):
    # Edith starts a new list in a way that causes a validation error:
    self.browser.get(self.server_url)
    self.get_item_input_box().send_keys('\n')
    error = self.browser.find_element_by_css_selector('.has-error')
    self.assertTrue(error.is_displayed()) #

    # She starts typing in the input box to clear the error
    self.get_item_input_box().send_keys('a')

    # She is pleased to see that the error message disappears
    error = self.browser.find_element_by_css_selector ...