diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..40215dd
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "src"]
+	path = python-tdd-book-src
+	url = ssh://git@lj918plus.dsmynas.com:2223/Jason/python-tdd-book-src.git
diff --git a/python-tdd-book-src b/python-tdd-book-src
new file mode 160000
index 0000000..76a8bf8
--- /dev/null
+++ b/python-tdd-book-src
@@ -0,0 +1 @@
+Subproject commit 76a8bf8aed1c901a3ff6a1f04c743b8230b79f50
diff --git a/textbook/chap3.md b/textbook/chap3.md
index 00b60f5..52701ef 100644
--- a/textbook/chap3.md
+++ b/textbook/chap3.md
@@ -6,7 +6,7 @@ Chap2 introduced writing a functional test using unittest module (expected failu
 
 * Django encourage structure the code into apps. We can reuse app developed by us or others
 
-Create an app `lists` (sub-directory) via `python manage.py startapp lists` along other `functional_tests.py` & `manage.py`, this subdir should include `tests.py` be default
+Create an app `lists` (sub-directory) via `python manage.py startapp lists` in the directory which contains `functional_tests.py` & `manage.py`, this subdir should include `tests.py` be default
 
 ## 3.2 Unit Tests, and How They Differ from Functional Tests
 
@@ -47,11 +47,11 @@ python manage.py test
 
 ## 3.4 Django's MVC, URLs, and View Functions
 
-Django is structured along a classic [**Model-View-Controller (MVC)** pattern](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller). 
+Django is structured along classic [**Model-View-Controller (MVC)** pattern](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller). 
 
 Django's main job is to decide what to do when a user asks for a particular URL on our site.
 
-Django's workflow is like:
+Django's workflow:
 
 1. An HTTP `request` comes in for a particular URL
 2. *Resolving the URL*: Django uses some rules to decide which `view` function should deal with the request.
@@ -62,9 +62,33 @@ Let's design a tests:
 1. Verify we can resolve the URL for the root of site ("/") to a particular view function we've made?
 2. Verify view function return some HTML which will get the functional test to pass?
 
+```python
+from django.test import TestCase
+from django.urls import resolve
+from lists.views import home_page
+
+class HomePageTest(TestCase):
+
+    def test_root_url_resolves_to_home_page_view(self):
+        found = resolve('/')
+        self.assertEqual(found.func, home_page)
+```
+
+Where:
+* The resolve() function if `django.url` package can be used for resolving URL paths to the corresponding view functions. The function returns a [`ResolverMatch` object](https://docs.djangoproject.com/en/3.1/ref/urlresolvers/#django.urls.ResolverMatch) that allows you to access various metadata about the resolved URL.
+* In `assertEqual(...)`, we try to test that `found.func` is `home_page` (a view function we haven't defined yet)
+
+Result of running test:
+
+```
+ImportError: cannot import name 'home_page'
+```
+
 ## 3.5 At Last! We Actually Write Some Application Code!
 
-Add content in `lists/views.py`, to pass the test
+In 3.4, we created a `test_root_url_resolves_to_home_page_view()` test case that check "django can resolve request to root and return a view function"
+
+Hence, add content in `lists/views.py`, we can pass the test
 
 ```python
 from django.shortcuts import render
@@ -72,6 +96,33 @@ from django.shortcuts import render
 home_page = None
 ```
 
+Running the test generate following info
+
+```
+Creating test database for alias 'default'...
+System check identified no issues (0 silenced).
+E
+======================================================================
+ERROR: test_root_url_resolves_to_home_page_view (lists.tests.HomePageTest)
+----------------------------------------------------------------------
+Traceback (most recent call last):
+  File "/home/jason/HomeWorkstation/SynologyGiteaSpace/python-tdd-book-src/src/lists/tests.py", line 8, in test_root_url_resolves_to_home_page_view
+    found = resolve('/')
+  File "/home/jason/miniconda3/envs/python-tdd-book/lib/python3.6/site-packages/django/urls/base.py", line 27, in resolve
+    return get_resolver(urlconf).resolve(path)
+  File "/home/jason/miniconda3/envs/python-tdd-book/lib/python3.6/site-packages/django/urls/resolvers.py", line 394, in resolve
+    raise Resolver404({'tried': tried, 'path': new_path})
+django.urls.exceptions.Resolver404: {'tried': [[<RegexURLResolver <RegexURLPattern list> (admin:admin) ^admin/>]], 'path': ''}
+
+----------------------------------------------------------------------
+Ran 1 test in 0.001s
+```
+
+* error due to `django.urls.exceptions.Resolver404: {'tried': [[<RegexURLResolver <RegexURLPattern list> (admin:admin) ^admin/>]], 'path': ''}`
+* Happen in `python-tdd-book-src/src/lists/tests.py", line 8, in test_root_url_resolves_to_home_page_view`
+
+Overall, the traceback can be interpreted as: "when trying to resolve `/`, Django raised a 404 error". i.e. Django can't find a URL mapping for "/"
+
 ## 3.6 urls.py
 
 
diff --git a/textbook/summary.md b/textbook/summary.md
new file mode 100644
index 0000000..4f2e4b5
--- /dev/null
+++ b/textbook/summary.md
@@ -0,0 +1,6 @@
+# Summary
+
+Summarize learning, for quick reference
+
+* Run Django server: `python manage.py runserver`
+* If test cases are created by framework, run it via: `python manage.py test`
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