From e4cb70719e59daba0b8942fa91cbe472a0613312 Mon Sep 17 00:00:00 2001
From: JasonHomeWorkstationUbuntu <jasonzhuyq@outlook.com>
Date: Mon, 9 Nov 2020 12:03:16 +1100
Subject: [PATCH] 5.7.1 Better Unit Testing Practice: Each Test Should Test One
 Thing

---
 textbook/chap5.md | 57 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/textbook/chap5.md b/textbook/chap5.md
index e0f120f..38546f1 100644
--- a/textbook/chap5.md
+++ b/textbook/chap5.md
@@ -280,4 +280,61 @@ def home_page(request):
     return render(request=request, template_name='home.html', context={
         'new_item_text': request.POST.get('item_text', ''),
     })
+```
+
+## 5.7 Redirect After a POST
+
+A view func has 2 jobs:
+1. Processing user input (save to database)
+2. Returning an appropriate response
+
+2nd one is our target in this section
+
+"Always redirect after a POST", change test case to save a POST request. So redirect back to home page, instead of rendering a response with item in it
+
+```python
+    def test_can_save_a_POST_request(self):
+        response = self.client.post('/', data={'item_text': 'A new list item'})
+
+        self.assertEqual(Item.objects.count(), 1)
+        new_item = Item.objects.first()
+        self.assertEqual(new_item.text, 'A new list item')
+
+        self.assertEqual(response.status_code, 302)
+        self.assertEqual(response['location'], '/')
+```
+
+* QUES: What mean redirect?
+* ANS: After sending POST, the returned response does not contain `.content` that rendered by a template, instead it's HTTP redirect that point to another URL
+
+Modify `views.py` to pass this UT
+
+```python
+def home_page(request):
+    if request.method == 'POST':
+        Item.objects.create(text=request.POST['item_text']) # Processing user input
+        return redirect('/') # Redirect back to home.html
+
+    return render(request=request, template_name='home.html')
+```
+
+### 5.7.1 Better Unit Testing Practice: Each Test Should Test One Thing
+
+Note: good UT practice is that each test should only test one thing.
+
+So, separate the test code into two:
+
+```python
+    def test_can_save_a_POST_request(self):
+        self.client.post('/', data={'item_text': 'A new list item'})
+
+        self.assertEqual(Item.objects.count(), 1)
+        new_item = Item.objects.first()
+        self.assertEqual(new_item.text, 'A new list item')
+
+    def test_redirects_after_POST(self):
+        response = self.client.post('/', data={'item_text': 'A new list item'})
+
+        self.assertEqual(response.status_code, 302)
+        self.assertEqual(response['location'], '/')
 ```
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