162 lines
4.9 KiB
Markdown
162 lines
4.9 KiB
Markdown
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# Chapter 4. What Are We Doing with All These Tests? (And, Refactoring)
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## 4.1 Programming is like pulling a bucket of water up from a well
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TDD is **discipline**. Its payoffs not come immediately
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## 4.2 Using selenium to test user interactions
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Modify `functional_tests.py` to test user interactions
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```python
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from selenium import webdriver
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from selenium.webdriver.common.keys import Keys
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import time
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import unittest
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class NewVisitorTest(unittest.TestCase):
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def setUp(self):
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self.browser = webdriver.Firefox()
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def tearDown(self):
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self.browser.quit()
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def test_can_start_a_list_and_retrieve_it_later(self):
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# Edith has heard about a cool new online to-do app. She goes
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# to check out its homepage
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self.browser.get('http://localhost:8000')
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# She notices the page title and header mention to-do lists
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self.assertIn('To-Do', self.browser.title)
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header_text = self.browser.find_element_by_tag_name('h1').text
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self.assertIn('To-Do', header_text)
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# She is invited to enter a to-do item straight away
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inputbox = self.browser.find_element_by_id('id_new_item')
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self.assertEqual(
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inputbox.get_attribute('placeholder'),
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'Enter a to-do item'
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)
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# She types "Buy peacock feathers" into a text box (Edith's hobby
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# is tying fly-fishing lures)
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inputbox.send_keys('Buy peacock feathers')
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# When she hits enter, the page updates, and now the page lists
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# "1: Buy peacock feathers" as an item in a to-do list
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inputbox.send_keys(Keys.ENTER)
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time.sleep(1)
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table = self.browser.find_element_by_id('id_list_table')
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rows = table.find_element_by_tag_name('tr')
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self.assertTrue(
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any(row.text == '1: Buy peacock feathers' for row in rows)
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)
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# There is still a text box inviting her to add another item. She
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# enters "Use peacock feathers to make a fly" (Edith is very methodical)
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self.fail('Finish the test!')
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# The page updates again, and now shows both items on her list
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# Edith wonders whether the site will remember her list. Then she sees
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# that the site has generated a unique URL for her -- there is some
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# explanatory text to that effect.
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# She visits that URL - her to-do list is still there.
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# Satisfied, she goes back to sleep
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if __name__ == '__main__':
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unittest.main(warnings='ignore')
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```
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Start django server and then run `python functional_tests.py`
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## 4.3 The "Don't Test Constants" Rule, and Templates to the Rescue
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Our object: test HTML.
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Problem: currently test case look for exact HTML string, directly test content within HTML using fixed string is not wise.
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Testing content within a HTML is not useful, as it's testing constant.
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Unit tests are about testing **logic**, **flow control**, and **configuration**.
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Using template is much better solution to test raw strings in Python.
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### 4.3.1 Refactoring to Use a Template
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Our object: refactor view function return the same HTML
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**Refactor** = improve the code *without changing its functionality*
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1. Create a html file in `lists/template` folder, in which Django look for template that used for the app
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2. django use `render` function to render the template, given request
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3. Add app into `superlists/settings.py`'s `INSTALLED_APPS` list, so django will search it
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Check commit 89224c9
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### 4.3.2 The Django Test Client
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Django provides **Django Test Client** which can be used to check what templates are used.
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```python
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request = HttpRequest() #1
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response = home_page(request) #2
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```
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can be replaced by (django test client)
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```python
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response = self.client.get('/') #1
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```
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And assert methods
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```python
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self.assertTrue(html.startswith('<html>'))
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self.assertIn('<title>To-Do lists</title>', html)
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self.assertTrue(html.strip().endswith('</html>'))
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```
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can be replaced by
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```python
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self.assertTemplateUsed(response, 'home.html') #3
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```
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Note: DJANGO TEST CLIENT is introduced until now because manual test steps are necessary for learning
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Check commit 747e0c7
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## 4.4 On Refactoring
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Tip: **When refactoring, work on either the code or the tests, but not both at once**, otherwise, changing both will quickly lead to change across multiple files and chaos
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## 4.5 A Little More of Our Front Page
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## Recap: The TDD Process
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Main aspects of TDD process:
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* Functional tests
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* Unit tests
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* The unit-test/code cycle
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* Refactoring
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Overall TDD process is:
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Ques: How does FT, UT cooperate with TDD?
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ANS: FT is a larger TDD cycle, while UTs are smaller TDD cycles
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1. Write a FT and see it fail.
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2. mini-TDD cycle of each unit test is employed to achieve small steps
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QUES: How does refactoring cooperate with TDD?
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ANS: Use a FT to check the behavior of app, FT is fixed but UTs can be add/removed
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Overall, it's a "Double-Loop TDD" as shown below
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