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--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
-.vscode
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+.vscode
+**__pycache__**
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diff --git a/chap11_testing.md b/chap11_testing.md
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--- /dev/null
+++ b/chap11_testing.md
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+# Chapter 11. Testing Your Code
+
+Learn how to test code using Python's `unittest` module.
+
+## Testing a Function
+
+Function to be tested as shown below.
+
+```python
+def get_formatted_name(first, last):
+    """Generate a neatly formatted full name."""
+    full_name = f"{first} {last}"
+    return full_name.title()
+```
+
+A script that should use `get_formatted_name` 
+
+```python
+from name_function import get_formatted_name
+
+print("Enter 'q' at any time to quit.")
+while True:
+    first = input("\nPlease give me a first name: ")
+    if first == 'q':
+        break
+    last = input("Please give me a last name: ")
+    if last == 'q':
+        break
+
+    formatted_name = get_formatted_name(first, last)
+    print(f"\tNeatly formatted name: {formatted_name}.")
+```
+
+To make sure `get_formatted_name` function properly, using `unittest` module of Python
+
+```python
+import unittest
+from name_function import get_formatted_name
+
+class NamesTestCase(unittest.TestCase):
+    """Test for name_function.py"""
+
+    def test_first_last_name(self):
+        """Do names like 'Janis Joplin' work?"""
+        formatted_name = get_formatted_name('janis', 'joplin')
+        self.assertEqual(formatted_name, 'Janis Joplin')
+
+if __name__ == '__main__':
+    unittest.main()
+```
+
+Key points:
+
+* Import `unittest` module as shown
+* Import function to be tested
+* Here, `unittest`'s most useful feature `assert` is used. `assertEqual` can compare two objects
+* `__name__` is a **special variable**, which is set when the program is executed. If the file is being run as the main program, the value of `__name__` is set to `'__main__'`
+
+Result of running this test:
+
+```
+.
+----------------------------------------------------------------------
+Ran 1 test in 0.000s
+
+OK
+```
+
+* First dot represent the single test passed.
+
+### A Failing Test
+
+Failure case returns 
+
+```
+F
+======================================================================
+FAIL: test_first_last_name (__main__.NamesTestCase)
+Do names like 'Janis Joplin' work?
+----------------------------------------------------------------------
+Traceback (most recent call last):
+  File "test_name_function.py", line 10, in test_first_last_name
+    self.assertEqual(formatted_name, 'Janis Joplins')
+AssertionError: 'Janis Joplin' != 'Janis Joplins'
+- Janis Joplin
++ Janis Joplins
+?             +
+
+
+----------------------------------------------------------------------
+Ran 1 test in 0.001s
+
+FAILED (failures=1)
+```
+
+Highlight:
+
+* `FAIL: test_first_last_name` tell's where the error coming from.
+
+## Fix them
+
+If employing TDD, we can first create test case, then develop code to be test against.
+
+## Testing a Class
+
+e.g. above shown how to write test case for single function, we also need to write test for class.
+
+### A Variety of Assert Methods
+
+Python `unittest` module provide various assert methods in `unittest.TestCase` class.
+
+List of available assert methods
+
+| Method                    | Use                              |
+| ------------------------- | -------------------------------- |
+| `assertEqual(a,b)`        | Verify `a == b`                  |
+| `assertNotEqual(a,b)`     | Verify that `a != b`             |
+| `assertTrue(x)`           | Verify that x is True            |
+| `assertFalse(x)`          | Verify that x is False           |
+| `assertIn(item, list)`    | Verify that item is in list      |
+| `assertNotIn(item, list)` | Verrify that item is not in list |
+
+### A Class to Test
+
+* class to be tested in *survey.py* have class `AnonymousSurvey`
+
+```python
+class AnonymousSurvey:
+    """Collect anonymous answers to a survey questions"""
+
+    def __init__(self, question):
+        """Store a question, and prepare to store response."""
+        self.question = question
+        self.responses = []
+
+    def show_question(self):
+        """Show the survey question"""
+        print(self.question)
+
+    def store_response(self, new_response):
+        """Store a single response to the survey"""
+        self.responses.append(new_response)
+
+    def show_results(self):
+        """Show all the responses that have been given"""
+        print("Survey results:")
+        for response in self.responses:
+            print(f"- {response}")
+```
+* script to use `AnonymousSurvey` *language_survey.py*
+
+```python
+from survey import AnonymousSurvey
+
+# Define a question, and make a survey.
+question = "What language did you first learn to speak?"
+my_survey = AnonymousSurvey(question)
+
+# Show the questions, and store responses to the question
+my_survey.show_question()
+print("Enter 'q' at any time to quit.\n")
+while True:
+    response = input("Language: ")
+    if response == 'q':
+        break
+    my_survey.store_response(response)
+
+# Show the survey results
+print("\nThank you to everyone who participate in the survey")
+my_survey.show_results()
+```
+
+If we want to 
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diff --git a/src/chap11/language_survey.py b/src/chap11/language_survey.py
new file mode 100644
index 0000000..57978fc
--- /dev/null
+++ b/src/chap11/language_survey.py
@@ -0,0 +1,18 @@
+from survey import AnonymousSurvey
+
+# Define a question, and make a survey.
+question = "What language did you first learn to speak?"
+my_survey = AnonymousSurvey(question)
+
+# Show the questions, and store responses to the question
+my_survey.show_question()
+print("Enter 'q' at any time to quit.\n")
+while True:
+    response = input("Language: ")
+    if response == 'q':
+        break
+    my_survey.store_response(response)
+
+# Show the survey results
+print("\nThank you to everyone who participate in the survey")
+my_survey.show_results()
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diff --git a/src/chap11/name_function.py b/src/chap11/name_function.py
new file mode 100644
index 0000000..045b966
--- /dev/null
+++ b/src/chap11/name_function.py
@@ -0,0 +1,4 @@
+def get_formatted_name(first, last):
+    """Generate a neatly formatted full name"""
+    full_name = f"{first} {last}"
+    return full_name.title()
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diff --git a/src/chap11/names.py b/src/chap11/names.py
new file mode 100644
index 0000000..57229dd
--- /dev/null
+++ b/src/chap11/names.py
@@ -0,0 +1,13 @@
+from name_function import get_formatted_name
+
+print("Enter 'q' at any time to quit.")
+while True:
+    first = input("\nPlease give me a first name: ")
+    if first == 'q':
+        break
+    last = input("Please give me a last name: ")
+    if last == 'q':
+        break
+
+    formatted_name = get_formatted_name(first, last)
+    print(f"\tNeatly formatted name: {formatted_name}.")
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diff --git a/src/chap11/survey.py b/src/chap11/survey.py
new file mode 100644
index 0000000..58e15fb
--- /dev/null
+++ b/src/chap11/survey.py
@@ -0,0 +1,21 @@
+class AnonymousSurvey:
+    """Collect anonymous answers to a survey questions"""
+
+    def __init__(self, question):
+        """Store a question, and prepare to store response."""
+        self.question = question
+        self.responses = []
+
+    def show_question(self):
+        """Show the survey question"""
+        print(self.question)
+
+    def store_response(self, new_response):
+        """Store a single response to the survey"""
+        self.responses.append(new_response)
+
+    def show_results(self):
+        """Show all the responses that have been given"""
+        print("Survey results:")
+        for response in self.responses:
+            print(f"- {response}")
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diff --git a/src/chap11/test_name_function.py b/src/chap11/test_name_function.py
new file mode 100644
index 0000000..b6f700e
--- /dev/null
+++ b/src/chap11/test_name_function.py
@@ -0,0 +1,13 @@
+import unittest
+from name_function import get_formatted_name
+
+class NamesTestCase(unittest.TestCase):
+    """Test for name_function.py"""
+
+    def test_first_last_name(self):
+        """Do names like 'Janis Joplin' work?"""
+        formatted_name = get_formatted_name('janis', 'joplin')
+        self.assertEqual(formatted_name, 'Janis Joplins')
+
+if __name__ == '__main__':
+    unittest.main()
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diff --git a/src/chap11/test_survey.py b/src/chap11/test_survey.py
new file mode 100644
index 0000000..f567d06
--- /dev/null
+++ b/src/chap11/test_survey.py
@@ -0,0 +1,15 @@
+import unittest
+from survey import AnonymousSurvey
+
+class TestAnonymousSurvey(unittest.TestCase):
+    """Tests for the class AnonymouseSurvey"""
+    
+    def test_store_single_response(self):
+        """Tests that a single response is stored properly"""
+        question = "What language did you first learn to speak?"
+        my_survey = AnonymousSurvey(question)
+        my_survey.store_response('English')
+        self.assertIn('English', my_survey.responses)
+
+if __name__ == '__main__':
+    unittest.main()
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