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Test-Driven Development with Python, 2nd Edition by Harry J.W. Percival

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Chapter 15. More Advanced Forms

Now let’s look at some more advanced forms usage. We’ve helped our users to avoid blank list items, so now let’s help them avoid duplicate items.

This chapter goes into more intricate details of Django’s form validation, and you have my official permission to skip it if you already know all about customising Django forms, or if you’re reading this book for the TDD rather than for the Django.

If you’re still learning Django, there’s good stuff in here. If you want to skip ahead, that’s OK too. Make sure you take a quick look at the aside on developer stupidity, and the recap on testing views at the end.

Another FT for Duplicate Items

We add a second test method to ItemValidationTest:

functional_tests/test_list_item_validation.py (ch13l001)

def test_cannot_add_duplicate_items(self):
    # Edith goes to the home page and starts a new list
    self.browser.get(self.live_server_url)
    self.get_item_input_box().send_keys('Buy wellies')
    self.get_item_input_box().send_keys(Keys.ENTER)
    self.wait_for_row_in_list_table('1: Buy wellies')

    # She accidentally tries to enter a duplicate item
    self.get_item_input_box().send_keys('Buy wellies')
    self.get_item_input_box().send_keys(Keys.ENTER)

    # She sees a helpful error message
    self.wait_for(lambda: self.assertEqual(
        self.browser.find_element_by_css_selector('.has-error').text,
        "You've already got this in your list"
    ))

Why have two test methods rather than extending one, or having a new file and class? It’s a judgement call. ...

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