7.3 Implementing the New Design Incrementally Using TDD

textbook/chap6.md

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+# Chapter 6. Improving Functional Tests: Ensuring Isolation and Removing Voodoo Sleeps
+
+## 6.1 Ensuring Test Isolation in Functional Tests
+
+* Problem left on scratchpad: Clean up after FT runs
+* Methods:
+  * 1. In `functional_tests.py` add in codes to delete database
+  * 2. Use class `LiveServerTestCase` (Django 1.4). It will create a test db and start up a dev server for functional tests
+
+How to use `LiveServerTestCase`:
+* It's derived from Django's `TestCase` class, so can be run by Django test runner
+* Django test runner search for all scripts start with `test`
+
+What to do?:
+1. Create a `functional_test` directory, i.e. create a *functional_test* app
+2. rename `functional_test.py` as `tests.py` and move it into `functional_test` directory
+3. Modify `tests.py` to let it use `LiveServerTestCase` as shown below, and instead of hardcoding visit to localhost port 8000, `LiveserverTestCase` provide attribute `live_server_url`.
+
+```python
+class NewVisitorTest(LiveServerTestCase):
+    ...
+
+    def test_can_start_a_list_and_retrieve_it_later(self):
+        # Edith has heard about a cool new online to-do app. She goes
+        # to check out its homepage
+        self.browser.get(self.live_server_url)
+```
+
+### 6.1.1 Running Just the Unit Tests
+
+We can specify what we want to run by
+
+```
+python manage.py test functional_tests
+```
+
+or
+
+```
+python manage.py test lists
+```
+
+## 6.2 Aside: Upgrading Selenium and Geckodriver
+
+Sometimes, mismatch between firefox and (Selenium + Geckodriver) may result failure in test, as firefox may auto upgrade itself at night. Upgrade Selenium + Geckodriver as follow:
+
+1. `pip install --upgrade selenium`
+2. Download new geckodriver
+
+## 6.3 On Implicit and Explicit Waits, and Voodoo time.sleeps
+
+Implicit Waits & Explicit Waits:
+* Implicit Waits: Selenium tries to wait "automatically" for you when it thinks the page is loading. But it's unstable, DON'T USE IT.
+* Explicit Waits: `time.sleep(...)` in FT. It's hard to set a fixed second (Voodoo Sleep). A while loop with try/except will be more better
+
+```python
+from selenium.common.exceptions import WebDriverException
+
+MAX_WAIT = 10 # Maximum amount of time we're prepared to wait
+[...]
+
+    def wait_for_row_in_list_table(self, row_text):
+        start_time = time.time()
+        while True:
+            try:
+                table = self.browser.find_element_by_id('id_list_table')
+                rows = table.find_elements_by_tag_name('tr')
+                self.assertIn(row_text, [row.text for row in rows])
+                return
+            except (AssertionError, WebDriverException) as e:
+                if time.time() - start_time > MAX_WAIT:
+                    raise e
+                time.sleep(0.5)
+```
+
+Replace all `check_for_row_in_list_table` with `wait_for_row_in_list_table`
+
+### "BEST PRACTICES" Applied in this Chapter
+
+* Ensuring test isolation and managing global state
+* Avoid "voodoo" sleeps (i.e. `time.sleep`)
+* Don't rely on Selenium's implicit waits

textbook/chap7.md

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+# Chapter 7. Working Incrementally
+
+Target: our design only allows one global list. Each user should have a separate list.
+
+TDD technique to learn: adapt existing code using an incremental, step-by-step process which takes you from working state to working state (avoid crashing).
+
+## 7.1 Small Design When Necessary
+
+### Not Big Design Up Front
+
+* Traditional software dev: *Big Design Up Front*
+* New software dev cycle: Agile, put MVP (Minimum Viable Product) out early, and let design evolve gradually
+
+Planning for MVP:
+* Each user can store their own list
+* A list is made up of several items, with a description as attribute
+* Saved List should be permanent
+
+### YAGNI!
+
+Agile gospel: YAGNI (You Aren't Gonna Need It). Don't overthink about design (e.g. username? list title?) No matter how cool the idea was, you won't end up using it.
+
+### REST(ish)
+
+* QUES: Our data structure sit in model of Model-View-Controller (MVC). How should View & Controller work?
+* ANS: **REST (Representational State Transfer)** is the usual approach to design web-based APIs. But currently we don't stick strickly to it. (Visit Appendix F for full REST API implementation)
+
+Design of our to-do list app:
+* REST suggest that URL structure should match our data structure. So each list have its own URL `/list/<list identifier>`
+* View a list: use GET request. (It's a normal browser visit to the page)
+* Create a brand new list: a special URL will accept POST requests `lists/new`
+* Add new item to list: have a separate URL to send POST requests `/lists/<list identifier>/add_item`
+
+## 7.2 Implementing the New Design Incrementally Using TDD
+
+![Implementing New Design using TDD](img/7-1.jpg)
+
+* On top-level, adding new feature by:
+  * 1. new FT
+  * 2. New app code
+  * 3. Refactor code
+* On UT level:
+  * Add/Modify tests to verify changes we make