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+\[ [Index](index.md) | [Exercise 5.5](ex5_5.md) | [Exercise 6.1](ex6_1.md) \]
+
+# Exercise 5.6
+
+*Objectives:*
+
+- Learn how to use Python's unittest module
+
+*Files Created:* `teststock.py`
+
+In this exercise, you will explore the basic mechanics of using
+Python's `unittest` modules.
+
+## (a) Preliminaries
+
+In previous exercises, you created a file `stock.py` that contained
+a `Stock` class.   In a separate file, `teststock.py`, define the following
+testing code:
+
+```python
+# teststock.py
+
+import unittest
+import stock
+
+class TestStock(unittest.TestCase):
+    def test_create(self):
+        s = Stock('GOOG', 100, 490.1)
+        self.assertEqual(s.name, 'GOOG')
+        self.assertEqual(s.shares, 100)
+        self.assertEqual(s.price, 490.1)
+
+if __name__ == '__main__':
+    unittest.main()
+```
+
+Make sure you can run the file:
+
+```
+ bash % python3 teststock.py
+ .
+ ------------------------------------------------------------------```
+ Ran 1 tests in 0.001s
+
+ OK
+ bash %
+```
+
+## (b) Unit testing
+
+Using the code in `teststock.py` as a guide, extend the `TestStock` class
+with tests for the following:
+
+- Test that you can create a `Stock` using keyword arguments such as `Stock(name='GOOG',shares=100,price=490.1)`.
+- Test that the `cost` property returns a correct value
+- Test that the `sell()` method correctly updates the shares.
+- Test that the `from_row()` class method creates a new instance from good data.
+- Test that the `__repr__()` method creates a proper representation string.
+- Test the comparison operator method `__eq__()`
+
+## (c) Unit tests with expected errors
+
+Suppose you wanted to write a unit test that checks for an exception.
+Here is how you can do it:
+
+```python
+class TestStock(unittest.TestCase):
+    ...
+    def test_bad_shares(self):
+        s = stock.Stock('GOOG', 100, 490.1)
+        with self.assertRaises(TypeError):
+             s.shares = '50'
+    ...
+```
+
+Using this test as a guide, write unit tests for the following failure modes:
+
+- Test that setting `shares` to a string raises a `TypeError`
+- Test that setting `shares` to a negative number raises a `ValueError`
+- Test that setting `price` to a string raises a `TypeError`
+- Test that setting `price` to a negative number raises a `ValueError`
+- Test that setting a non-existent attribute `share` raises an `AttributeError`
+
+In total, you should have around a dozen unit tests when you're done.
+
+**Important Note**
+
+For later use in the course, you will want to have a fully working
+`stock.py` and `teststock.py` file.  Save your work in progress if you
+have to, but you are strongly encouraged to copy the code from
+`Solutions/5_6` if things are still broken at this point.
+
+We're going to use the `teststock.py` file as a tool for improving the `Stock` code
+later.  You'll want it on hand to make sure that the new code behaves the same way
+as the old code.
+
+\[ [Solution](soln5_6.md) | [Index](index.md) | [Exercise 5.5](ex5_5.md) | [Exercise 6.1](ex6_1.md) \]
+
+----
+`>>>` Advanced Python Mastery  
+`...` A course by [dabeaz](https://www.dabeaz.com)  
+`...` Copyright 2007-2023  
+
+![](https://i.creativecommons.org/l/by-sa/4.0/88x31.png). This work is licensed under a [Creative Commons Attribution-ShareAlike 4.0 International License](http://creativecommons.org/licenses/by-sa/4.0/)