---
id: practical-python-8.1
source_exercise_id: "8.1"
title: "Writing Unit Tests"
section: "8.1 Testing"
source_path: "08_Testing_debugging/01_Testing.md"
source_repo: "https://github.com/dabeaz-course/practical-python"
source_commit: "93dca856b41c61a0a0f85ae334116e4c125629ea"
student_visible_solution: false
has_private_solution: true
skip: false
---

# Exercise 8.1: Writing Unit Tests

> Source: Practical Python Programming, `08_Testing_debugging/01_Testing.md`.

### Exercise 8.1: Writing Unit Tests

In a separate file `test_stock.py`, write a set a unit tests
for the `Stock` class.   To get you started, here is a small
fragment of code that tests instance creation:


```python
# test_stock.py

import unittest
import stock

class TestStock(unittest.TestCase):
    def test_create(self):
        s = stock.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()
```

Run your unit tests.   You should get some output that looks like this:

```
.
----------------------------------------------------------------------
Ran 1 tests in 0.000s

OK
```

Once you're satisfied that it works, write additional unit tests that
check for the following:

- Make sure the `s.cost` property returns the correct value (49010.0)
- Make sure the `s.sell()` method works correctly.  It should
  decrement the value of `s.shares` accordingly.
- Make sure that the `s.shares` attribute can't be set to a non-integer value.

For the last part, you're going to need to check that an exception is raised.
An easy way to do that is with code like this:

```python
class TestStock(unittest.TestCase):
    ...
    def test_bad_shares(self):
         s = stock.Stock('GOOG', 100, 490.1)
         with self.assertRaises(TypeError):
             s.shares = '100'
```

[Contents](../Contents.md) \| [Previous (7.5 Decorated Methods)](../07_Advanced_Topics/05_Decorated_methods.md) \| [Next (8.2 Logging)](02_Logging.md)

## 关联来源

- [[summaries/01_Testing]]