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Test Setup and Teardown within a unittest.TestCase

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Sometimes we want to prepare a context for each test to be run under. The setUp method is run prior to each test in the class. tearDown is run at the end of every test. These methods are optional. Remember that TestCases are often used in cooperative multiple inheritance so you should be careful to always call super in these methods so that base class’s setUp and tearDown methods also get called. The base implementation of TestCase provides empty setUp and tearDown methods so that they can be called without raising exceptions: 

import unittest

class SomeTest(unittest.TestCase):
    def setUp(self):
        super(SomeTest, self).setUp()
        self.mock_data = [1,2,3,4,5]

    def test(self):
        self.assertEqual(len(self.mock_data), 5)

    def tearDown(self):
        super(SomeTest, self).tearDown()
        self.mock_data = []

if __name__ == '__main__':
    unittest.main()

Note that in python2.7+, there is also the addCleanup method that registers functions to be called after the test is run. In contrast to tearDown which only gets called if setUp succeeds, functions registered via addCleanup will be called even in the event of an unhandled exception in setUp. As a concrete example, this method can frequently be seen removing various mocks that were registered while the test was running: 

import unittest
import some_module

class SomeOtherTest(unittest.TestCase):
    def setUp(self):
        super(SomeOtherTest, self).setUp()
        
        # Replace `some_module.method` with a `mock.Mock`
        my_patch = mock.patch.object(some_module, 'method')
        my_patch.start()

        # When the test finishes running, put the original method back.
        self.addCleanup(my_patch.stop)

Another benefit of registering cleanups this way is that it allows the programmer to put the cleanup code next to the setup code and it protects you in the event that a subclasser forgets to call super in tearDown.

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Unit Testing:
* Unit Testing
* Setting up py.test
* Test Setup and Teardown within a unittest.TestCase
* Intro to Test Fixtures
* Asserting on Exceptions
* Failing Tests
* Testing Exceptions
* Choosing Assertions Within Unittests
* Mocking functions with unittest.mock.create autospec
* Unit tests with pytest
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68 pip PyPI Package Manager
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79 PyInstaller - Distributing Python Code
80 Iterables and Iterators
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83 args and kwargs
84 functools module
85 Garbage Collection
86 Indentation
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88 Pickle data serialization
89 urllib
90 Binary Data
91 Python and Excel
92 Idioms
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94 Difference between a module and a package
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98 PostgreSQL
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102 Creating temporary files with tempfile
103 Working with ZIP files
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108 Deployment using conda
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115 Alternatives to switch statement from other languages
116 List destructuring
117 Accessing Python source code and bytecode
118 Mixins
119 Attribute Access
120 ArcPy
121 Python Anti-Patterns
122 Plugin and Extension Classes
123 Websockets
124 Immutable data types
125 String representations of class
126 Arrays
127 Operator Precedence
128 Polymorphism
129 Alternative Python implementations
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131 Web Server Gateway Intrerface WSGI
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135 Unicode
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138 Neo4j
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143 Testing with py.test
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145 heapq
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148 Defining functions with list arguments
149 SQLite3 module
150 Persistence with pickle
151 Connecting to SQL Server
152 Design Patterns
153 Multidimensional arrays
154 Audio
155 pyglet
156 queue module
157 ijson
158 webbrowser module
159 base64 module
160 Flask
161 Groupby
162 Sockets and Message Encryption / Decryption
163 pygame
164 Input Subset and Output External Data Files using Pandas
165 hashlib
166 Gzip
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168 Creating a Windows Service
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170 configparser
171 Common Exceptions
172 Optical Character Recognition OCR
173 Python Data Types
174 Partial functions
175 Generating graphs
176 Unzipping Files
177 Functional Programming
178 Python Virtual Environment - virtualenv
179 sys module
180 virtual environment with virtualenvwrapper
181 virtualenvwrapper on Windows
182 Python Requests Post
183 Plotting with Matplotlib
184 Python Lex-Yacc
185 pyaudio
186 shelve
187 pip and PyPI Package Manager
188 Writing to CSV from String or List
189 Raise Custom Errors Exceptions
190 Using loops within functions
191 Contributors