how to make a python test driven development environment on Windows without Windows Subsystem for Linux¶

This is one way to make a Python Test Driven Development project on a Windows Computer that does NOT have Windows Subsystem for Linux. First, I do it manually where I make all the folders (directories) and files for the environment, including setting up the first test, then I write a program to do it for me

preview¶

Here is the program I have by the end of the chapter to automatically make a python test driven development environment, it is only 27 lines of code, with spaces

$PROJECT_NAME=$args[0]
mkdir $PROJECT_NAME
cd $PROJECT_NAME
mkdir src
New-Item "src/$PROJECT_NAME.py"
mkdir tests
New-Item tests/__init__.py

"import unittest


class Test$($PROJECT_NAME)(unittest.TestCase):

    def test_failure(self):
        self.assertFalse(True)


# Exceptions Encountered
# AssertionError
" | Out-File "tests/test_$PROJECT_NAME.py" -Encoding UTF8

python -m venv .venv
.venv/scripts/activate.ps1
python -m pip install --upgrade pip
"pytest-watch" | Out-File requirements.txt -Encoding UTF8
python -m pip install --requirement requirements.txt
pytest-watch

questions about making a Python Test Driven Development Environment on Windows without Windows Subsystem for Linux¶

Here are questions you can answer after going through this chapter

what is a Test Driven Development Environment?
How can I make a Python Test Driven Development Environment manually?
How can I make a Python Test Driven Development Environment automatically?
How can I change directories?
How can I make a directory?
How can I see directory structure?
How can I make an empty file?
How can I write text to a file?
How can I change the name of a file?
How can I run a Python Program?
How can I test for failure?
How can I make a Python package?
How can I run tests manually?
How can I run tests automatically?
How can I stop automated Python tests from running?
What is a Virtual Environment?
How can I make a Virtual Environment?
How can I activate a Virtual Environment?
How can I deactivate a Virtual Environment?
How can I document the Python programs my project needs?
How can I install the Python programs my project needs from a file?
How can I install Python packages in a Virtual Environment?
How can I see what Python packages are installed in a Virtual Environment?
How can I view all the commands I type in a terminal?
How can I make a PowerShell script?
What is a variable?
How can I use a variable in a PowerShell script
How can I run a PowerShell script

requirements¶

download and install Python
get an Integrated Development Environment (IDE). Here are a few options

how to manually make a python test driven development environment on Windows without Windows Subsystem for Linux¶

I pick magic as the name for this project

I open Terminal in the menu bar at the top of the Integrated Development Environment (IDE), then click New Terminal to open a terminal
I change directory to where I will put all the projects from this book. I type cd in the terminal

Note

You can skip this step if you are already in the pumping_python directory
```
cd pumping_python
```
the terminal shows
```
cd: no such file or directory: pumping_python
```
the folder (directory) does NOT exist. I need to make it
I use the mkdir program to make the pumping_python folder (directory)
```
mkdir pumping_python
```

the terminal goes back to the command line

I try changing directory again
```
cd pumping_python
```
the terminal shows I am now in the pumping_python folder (directory)
```
...\pumping_python >
```
I type tree in the terminal to see what files and folders are in the pumping_python directory
```
tree /F
```
the terminal shows
```
C:.
No subfolders exist
```
Note

There will be more files and folders if you have done other work in the pumping_python folder
I change directory to the magic project in the pumping_python folder
```
cd magic
```
the terminal shows
```
cd: no such file or directory: magic
```
the magic folder does NOT exist yet
I make the magic directory
```
mkdir magic
```
this makes a folder (directory) for the project where its files will stay
I use tree again
```
tree /F
```
the terminal shows
```
.
└── magic
```
I try cd again
```
cd magic
```
the terminal shows I am now in the magic folder I just made in the pumping_python folder
```
...\pumping_python\magic >
```

how to run a Python program on Windows without Windows Subsystem for Linux¶

I use Python to run the magic program

python src/magic.py

the terminal shows

python: can't open file '...\pumping_python\magic\src\magic.py': [Errno 2] No such file or directory

the computer cannot find the program because it does not exist, yet

I make a child folder in the magic directory for the program
```
mkdir src
```
the terminal goes back to the command line
I use tree to see what changed in the magic directory
```
tree /F
```
the terminal shows
```
.
└── src
```
I try to run the magic program again
```
python src/magic.py
```
the terminal shows the same error from before. I have to make the file

how to make an empty file on Windows without Windows Subsystem for Linux¶

I use New-Item to make an empty file in the src folder
```
New-Item src/magic.py
```
the terminal goes back to the command line
I use tree to see what folders and files I now have
```
tree /F
```
the terminal shows
```
.
└── src
    └── magic.py
```
New-Item is a command that makes an empty file with the name. I can give it the directory I want to put the file in as part of the name, in this case New-Item src/magic.py makes a file named magic.py in the src folder
I try to run the magic program again
```
python src/magic.py
```
the terminal goes back to the command line. Success! Even though magic.py does not do anything because there is no code in it, I can successfully run it because it exists.

test_failure on Windows without WSL¶

how to manually run tests on Windows without WSL¶

I use the unittest module from the Python standard library that comes with Python to run tests. I type this in the terminal
```
python -m unittest
```
the terminal shows
```
----------------------------------------------------------------------
Ran 0 tests in 0.000s

NO TESTS RAN
```
- python is the Python program
- -m is an option/switch passed when calling Python to run the module - unittest in this case
- a Python module is any file that ends with .py, this means somewhere on the computer there is a file named unittest.py, see the source code for unittest here
I do not have any tests yet, so there is nothing to run. I make a child folder to keep the tests separate from the actual program
```
mkdir tests
```

the terminal goes back to the command line

I use tree to see what my project looks like

tree /F

the terminal shows

.
├── src
│   └── magic.py
└── tests

I use New-Item to add an empty file to the tests directory for the actual test
```
New-Item tests/magic.py
```
the terminal goes back to the command line

I use tree to see what the project looks like so far

tree /F

the terminal shows

.
├── src
│   └── magic.py
└── tests
    └── magic.py

I run the test again
```
python -m unittest
```
the terminal shows
```
NO TESTS RAN
```

RED: make it fail¶

I open tests/magic.py with the Integrated Development Environment (IDE) to open it in the editor
Tip

I can open a file from the terminal in Visual Studio Code by typing code and the name of the file, for example
```
code tests/magic.py
```
I can also open a file by using ctrl on the keyboard and clicking with the mouse on the name of the file
I add the Python code below in tests/magic.py in the editor

Note

the line numbers below are a guide, you do not need to copy them
```
1import unittest
2
3
4class TestMagic(unittest.TestCase):
5
6    def test_failure(self):
7        self.assertFalse(True)
```
Here is an explanation of the code I typed in the file
- import unittest imports the unittest module from the Python standard library, this is what I am using for testing
- class TestMagic
  - class is the Python keyword for making classes - a group of attributes (values) and methods (functions) that belong together, I cover this in more detail in the classes chapter
  - TestMagic is the name I gave this class and will hold the test
    
    Important
    
    I can use any name for the test class, it MUST start with Test or unittest will NOT run the tests in it
  - unittest.TestCase is a class from the unittest module that has methods for testing
  - class TestMagic(unittest.TestCase) defines TestMagic as a “child” of unittest.TestCase which means I can use its methods and attributes
- def test_failure
  - def is the Python keyword for making methods (functions), see functions for more
  - test_failure is the name I used method for this first test
    
    Important
    
    I can use any name for the test method, it MUST start with test_ or unittest does NOT run the tests in it
  - self. lets me use attributes and methods of the TestMagic class which is a “child” of the unittest.TestCase class, instead of using TestMagic(). or unittest.TestCase().
    
    Important
    
    the name self is Python convention. I can use any name but it is easier to stick with convention for this concept
  - self.assertFalse(True) is an assertion
    - assertFalse is a method in the unittest.TestCase class that checks if its input is False
    - True is given as the input
    I expect this line to fail because True is not False. If it does not fail, then Python and I have a problem
I turn on the Auto Save feature in the Integrated Development Environment (IDE) to automatically save files when I make a change so that I do not repeat myself by hitting save (ctrl+s (Windows/Linux) or command+s (mac)) every time I make a change

Attention

Turn on the Auto Save feature in your Integrated Development Environment (IDE)
I try the command again to run the tests in the terminal
```
python -m unittest
```
the terminal shows
```
NO TESTS RAN
```
I need to tell Python that the tests folder is a Python package, so it can find the tests

how to make a Python package on Windows without WSL¶

I use New-Item to add an empty file with the name __init__.py in the tests folder

Attention

make sure to use 2 underscores (__) before and after init for __init__.py
```
New-Item tests/__init__.py
```
the terminal goes back to the command line

I run the tree command to see what changed

tree /F

the terminal shows

.
├── src
│   └── magic.py
└── tests
    ├── __init__.py
    └── magic.py

I try to run the tests again
```
python -m unittest
```
the terminal shows
```
NO TESTS RAN
```
I need to tell Python that magic.py in the tests folder is a test file
I close magic.py in the editor of the Integrated Development Environment (IDE)

Caution

if you do not close magic.py you will end up with 3 files in the tests folder after the next step (instead of 2), because the Auto Save feature (enabled earlier) will save the original file after you change its name

how to change the name of a file on Windows without WSL¶

I use the Move-Item command to change the name of magic.py in the tests folder to test_magic.py
```
Move-Item tests/magic.py tests/test_magic.py
```
the terminal goes back to the command line
I use tree to see what I have so far
```
tree /F
```
the terminal shows

Note

if you do not see __pycache__ in the list do not worry, the important thing is that you renamed magic.py to test_magic.py for unittest to find the test
```
.
├── src
│   └── magic.py
└── tests
    ├── __init__.py
    ├── __pycache__
    └── test_magic.py
```

I run the tests again

python -m unittest

the terminal shows AssertionError

F
=============================================================
FAIL: test_failure (tests.test_magic.TestMagic.test_failure)
-------------------------------------------------------------
Traceback (most recent call last):
  File "...pumping_python/magic/tests/test_magic.py", line 7, in test_failure
    self.assertFalse(True)
    ~~~~~~~~~~~~~~~~^^^^^^
AssertionError: True is not false

-------------------------------------------------------------
Ran 1 test in A.XYZs

FAILED (failures=1)

Important

I can use any name for the test file but it must start with test_ or unittest will NOT run the tests in the file

This is the RED part of the Test Driven Development cycle. The message in the terminal is about the failure, I like to read these from the bottom up, here is an explanation of each line, starting from the last line on the screen
- FAILED (failures=1) the number of failures
- Ran 1 test in A.XYZs the number of tests it ran and how long they took
- AssertionError: True is not false the Error (Exception) that happened and its message, in this case AssertionError because True is not False
- self.assertFalse(True) the line of code that caused AssertionError
- ~~~~~~~~~~~~~~~~^^^^^^ points to the part of the line above that Python thinks caused the error
- File ".../magic/tests/test_magic.py", line 7, in test_failure the line number of the code that caused the error and the location of the file where it is
- Traceback (most recent call last): all the information shown after this line that is indented to the right shows the calls that led to the failure, this is why I like to read it from the bottom up
- FAIL: test_failure (tests.test_magic.TestMagic.test_failure) is a header with information in dot notation about the failing test method
  - tests.test_magic.TestMagic.test_failure is the location of the failing test
  - tests is the tests folder
  - test_magic is the test_magic.py file in the tests directory
  - TestMagic is the class defined on line 4 in test_magic.py
  - test_failure is the method (function) defined on line 6 in test_magic.py
- F shows a failure
I hold ctrl on the keyboard and use the mouse to click on File ".../pumping_python/magic/tests/test_magic.py", line 7 in the terminal, and the Integrated Development Environment (IDE) opens the file in the editor with the cursor at the line where the failure happened

GREEN: make it pass¶

I change True to False on line 7 of test_magic.py in the editor

        self.assertFalse(False)

I run the test again in the terminal

python -m unittest

the test passes! The terminal shows

.
------------------------------------------------------
Ran 1 test in A.XYZs

OK

cue CELEBRATION MUSIC AND DANCE! I am GREEN!!

REFACTOR: make it better¶

Keep a list of Errors/Exceptions that show up in the terminal as you go through this book to know them better, it helps when you run into them later. I add a list with AssertionError in test_magic.py in the editor

import unittest

class TestMagic(unittest.TestCase):

    def test_failure(self):
        self.assertFalse(True)

# Exceptions Encountered
# AssertionError

I ran python -m unittest a few times to see the test fail, I ran python -m unittest again to see the test pass. I will have to run python -m unittest again when I add any code, to make sure tests that were passing do not start failing and that the new code I add does what I want.

This means I have to run python -m unittest for each part of the Test Driven Development cycle or any time there is a code change.

I do not want to type python -m unittest again, it is better for a computer program to run the tests so that I do not repeat myself.

how to automatically run tests on Windows without Windows Subsystem for Linux¶

I can use pytest-watch to run tests automatically. It is a Python program that automatically runs pytest any time a Python file changes in the folder it is looking at, this means it will run the tests for me every time I make a change.

pytest is a Python package like unittest, it is not first_inputart of the Python standard library

I type it in the terminal

pytest-watch

the terminal shows

command not found: pytest-watch

I need to install pytest-watch for the computer to use it. Next, I set up a virtual environment to keep programs my project needs in one place

how to make a virtual environment on Windows without WSL¶

I can install pytest-watch globally (for the entire computer), which means it will always be available to any project on the computer, but a better way would be to put it in a virtual environment so that it is installed only for this project.

what is a virtual environment?¶

A virtual environment is a separate folder where I can install Python packages that my project needs. This helps me keep things that belong to the project in one place, separate from other things on the computer.

It means I can have a separate virtual environment for every project with only the programs that the project needs. This helps if I decide to package the program to send to someone else, because everything needed by the project is in one place.

I make a virtual environment with the venv module from the Python standard library
```
python -m venv .venv
```
the terminal goes back to the command line
- python is the Python program
- -m is an option passed to Python to run the module given after the option
- venv is a module from the Python standard library, it is used to make a virtual environment with a given name
- .venv is the name I am giving for this virtual environment
  
  Important
  
  .venv is Python convention, I can use any name I want for the virtual environment

I run tree

tree /F

the terminal shows

.
├── src
│   └── magic.py
├── tests
│   ├── __init__.py
│   ├── __pycache__
│   └── test_magic.py
└── .venv
    ├── bin
    ├── .gitignore
    ├── include
    ├── lib
    ├── lib64 -> lib
    └── pyvenv.cfg

there is now a folder named .venv for the virtual environment

how to activate a virtual environment on Windows without WSL¶

I run PowerShell in Administrator mode and set the Execution Policy for the activation script to work

Set-ExecutionPolicy RemoteSigned

the terminal may show the following message if you have never run this command before

The execution policy helps protect you from scripts that you do not trust.
Changing the execution policy might expose you to the security risks
described in the about_Execution_Policies help topic at
https:/go.microsoft.com/fwlink/?LinkID=135170.
Do you want to change the execution policy?

[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend  [?] Help (default is "N"):

Type A to accept the change and it enables scripts that have been signed by a verified publisher to run on your computer, you can read more at Set-ExecutionPolicy

When I want to work in a virtual environment, I make sure I am in the parent directory of it, for example, magic in this case. I activate the virtual environment in the terminal to use it
```
.venv/scripts/activate.ps1
```
the terminal shows
(.venv) .../magic $
the (.venv) on the far left of the command line in the terminal shows that I am in the virtual environment
I run pytest-watch again
```
pytest-watch
```
the terminal shows
```
command not found: pytest-watch
```
I have to install pytest-watch in the virtual environment to use it in the virtual environment

how to see what packages are installed in a virtual environment on Windows without WSL¶

I use the Python package manager (pip) to see what Python packages are installed in the virtual environment I just made

pip list

the terminal shows

Package Version
------- -------
pip     x.y

pytest-watch is not in the list
pip is a module from the Python standard library, it is used to install Python packages

how to write text to a file on Windows without Windows Subsystem for Linux¶

I want to make a file where I can list all the Python packages for my project as a way to document it and have pip install the programs listed in the file

I can write text to a file with the echo program, it shows whatever it is given as an argument, on the screen (standard output (stdout)) for example
```
echo "pytest-watch"
```
the terminal shows
```
pytest-watch
```
I can use it to write text to a file by giving the file name with an operator
```
echo "pytest-watch" > requirements.txt
```
> is an operator that is used to send output from a program to the given file
I can also use Out-File to add text to a file, I use it to make the requirements file with pytest-watch as its text
```
"pytest-watch" | Out-File requirements.txt
```
- | is an operator that is used to send output to a program
- Out-File is a program that can be used to write text to a file
- pytest-watch is a Python program that automatically runs pytest when a Python file in the folder changes
- pytest is a Python package like unittest, that is used for testing
- requirements.txt is the name of a file where I can list Python packages for pip to install. The name requirements.txt is Python convention, I can use any name I want for the requirements file

I run tree to see what the project looks like now

tree /F

the terminal shows

.
├── requirements.txt
├── src
│   └── magic.py
├── tests
│   ├── __init__.py
│   ├── __pycache__
│   └── test_magic.py
└── .venv
    ├── bin
    ├── .gitignore
    ├── include
    ├── lib
    ├── lib64 -> lib
    └── pyvenv.cfg

requirements.txt is now in the magic folder

how to see what is inside a file on Windows without WSL¶

I can use the cat program to see what is inside a file. I use it to make sure my requirements.txt has pytest-watch inside it

cat requirements.txt

the terminal shows

pytest-watch

life is good!

how to install Python packages in a virtual environment on Windows without WSL¶

I use pip to install pytest-watch from the requirements file
```
python -m pip install --requirement requirements.txt
```
- --requirement is an option that can be passed to the install argument for Python packages in a given file
- requirements.txt is the name of the given file
the terminal shows programs being downloaded and installed, and when I do not have the latest version of pip installed, it shows this at the end
```
[notice] A new release of pip is available: XY.Z -> AB.C
[notice] To update, run: pip install --upgrade pip
```
I upgrade pip to the latest version. I recommend you do this every time you are in a virtual environment, it is good practice to update package managers to the latest version available
```
python -m pip install --upgrade pip
```
- install is an argument given to pip to install a given Python package
- --upgrade is an option that can be passed to the install argument, like --requirement from earlier, this one tells pip to upgrade the version of the given Python package
- pip is the Python package I am giving pip to install, in this case it upgrades itself to the latest version since I did not give a version number
Note

I can also tell pip to install pytest-watch directly without using a requirements file, the problem is it will not document what programs my project needs. I would either have to remember later or use pip list. It also does not help someone else who is trying to run my project later, know what programs it needs without me
```
python -m pip install pytest-watch
```
I check what Python packages are now installed in the virtual environment
```
pip list
```
the terminal shows
```
Package      Version
------------ -------
colorama     x.y.z
docopt       x.y.z
iniconfig    x.y.z
packaging    x.y
pip          x.y
pluggy       x.y.z
Pygments     x.y.z
pytest       x.y.z
pytest-watch x.y.z
watchdog     x.y.z
```
pytest-watch is in the list. Yes!

Tip

imagine that the pytest-watch project also has a requirements file with colorama, docopt, iniconfig, packaging, pluggy, Pygments, pytest and watchdog as programs that it needs to run and they got installed when I asked pip to install pytest-watch from the requirements.txt file

I try to run the tests again

pytest-watch

and it shows results without going back to the command line

================== test session starts===================
...
rootdir: .../magic
collected 1 item

tests/test_magic.py .                              [100%]

=============== 1 passed in X.YZs =======================

I hold ctrl on the keyboard and click on tests/test_magic.py to place the cursor in the editor of the Integrated Development Environment (IDE), then I change False to True on line 7

      self.assertFalse(True)

the terminal shows AssertionError

====================================== FAILURES =======================================
_______________________________ TestMagic.test_failure ________________________________

self = <tests.test_magic.TestMagic testMethod=test_failure>

    def test_failure(self):
>       self.assertFalse(True)
E       AssertionError: True is not false

tests/test_magic.py:7: AssertionError
============================== short test summary info ================================
FAILED tests/test_magic.py::TestMagic::test_failure - AssertionError: True is not false
================================= 1 failed in X.YZs ===================================

I hold ctrl on the keyboard and click on tests/test_magic.py:7 to place the cursor in the editor of the Integrated Development Environment (IDE), then I change True back to False in test_magic.py

      self.assertFalse(False)

the test passes and I can write the rest of the code for the project as the tests run automatically in response to any change I make

how to exit the automated tests on Windows without WSL¶

I exit the tests in the terminal by pressing ctrl+c on the keyboard

how to deactivate a virtual environment on Windows without WSL¶

I leave the virtual environment by typing this in the terminal
```
deactivate
```
I try pytest-watch again to show that I do not have it installed outside the virtual environment
```
pytest-watch
```
the terminal shows
```
command not found: pytest-watch
```
I change directory to the parent of magic
```
cd ..
```
.. is shorthand for the parent of any directory you are in. The terminal shows
```
...\pumping_python >
```
I am back in the pumping_python folder

how to automatically make a python test driven development environment on Windows without Windows Subsystem for Linux¶

You made it this far and have become the greatest programmer in the world. To follow The Do Not Repeat Yourself (DRY) Principle, I write a program that has all the commands it took to get here, then I can use that program to make a Test Driven Development Environment anytime I want and not have to remember every step of the process

how to make a PowerShell script¶

I use New-Item to make an empty file with a name that is easy to remember later and describes the program that will automatically make a Test Driven Development environment for me
```
New-Item makePythonTdd.ps1
```
the terminal goes back to the command line

I use tree to see what is in the pumping_python directory

tree /F

the terminal shows my new file is in the same parent directory of the magic project

.
├── magic
│   ├── .pytest_cache
│   ├── requirements.txt
│   ├── src
│   ├── tests
│   └── .venv
└── makePythonTdd.ps1

how to view all the commands I typed in a terminal on Windows without WSL¶

I type history in the terminal to see all the commands I have typed so far

history

the terminal shows

cd pumping_python
mkdir pumping_python
cd pumping_python
tree /F
cd magic
mkdir magic
tree /F
cd magic
python src/magic.py
mkdir src
tree /F
python src/magic.py
New-Item src/magic.py
tree /F
python src/magic.py
python -m unittest
mkdir tests
tree /F
New-Item tests/magic.py
tree /F
python -m unittest
New-Item tests/__init__.py
tree /F
python -m unittest
mv tests/magic.py tests/test_magic.py
tree /F
python -m unittest
pytest-watch
python -m venv .venv
tree /F
tree /F
.venv/scripts/activate.ps1
pytest-watch
pip list
echo "pytest-watch"
echo "pytest-watch" > requirements.txt
"pytest-watch" | Out-File requirements.txt -Encoding UTF8
tree /F
python -m pip install --requirement requirements.txt
python -m pip install --upgrade pip
pip list
pytest-watch
deactivate
pytest-watch
cd ..
New-Item makePythonTdd.ps1
tree /F

the history program shows all the commands I typed in the terminal so far, and I use them to write the program that will automatically make a Python Test Driven Development environment for me

I open makePythonTdd.ps1 in the editor of the Integrated Development Environment (IDE), then add the commands I used to make the magic project to the file

Note

the line numbers below are a guide, you do not need to copy them

mkdir magic
cd magic
mkdir src
New-Item src/magic.py
mkdir tests
New-Item tests/__init__.py
New-Item tests/test_magic.py
python -m venv .venv
.venv/scripts/activate.ps1
python -m pip install --upgrade pip
"pytest-watch" | Out-File requirements.txt -Encoding UTF8
python -m pip install --requirement requirements.txt
pytest-watch

I change New-Item to Out-File to add text for the first failing test to test_magic.py in makePythonTdd.ps1
```
7"" | Out-File "tests/test_magic.py" -Encoding UTF8
```

I add the text for the test like I did with test_magic.py inside the quotes (“”) I just added to makePythonTdd.ps1

Caution

Indentation is important in Python, I use 4 spaces as convention in this book, see rge Python Style Guide for more

mkdir magic
cd magic
mkdir src
New-Item src/magic.py
mkdir tests
New-Item tests/__init__.py

"import unittest


class TestMagic(unittest.TestCase):

    def test_failure(self):
        self.assertFalse(True)



# Exceptions Encountered
# AssertionError" | Out-File "tests/test_magic.py" -Encoding UTF8

python -m venv .venv
.venv/Scripts/activate.ps1
python -m pip install --upgrade pip
"pytest-watch" | Out-File requirements.txt -Encoding UTF 8
python -m pip install --requirement requirements.txt
pytest-watch

how to run a PowerShell script¶

I go back to the terminal to run the program

makePythonTdd.ps1

the terminal shows

command not found: makePythonTdd.ps1

I have to tell the computer where the file is

.\makePythonTdd.ps1

.\ is shorthand for this directory which in this case is pumping_python where makePythonTdd.ps1 is saved. The terminal shows

======================================= FAILURES =======================================
________________________________ TestMagic.test_failure ________________________________

self = <tests.test_magic.TestMagic testMethod=test_failure>

    def test_failure(self):
>       self.assertFalse(True)
E       AssertionError: True is not false

tests/test_magic.py:7: AssertionError
=============================== short test summary info ================================
FAILED tests/test_magic.py::TestMagic::test_failure - AssertionError: True is not false
================================== 1 failed in X.YZs ===================================

Success! I just made a program that can make the magic project anytime I want and it automatically does the steps I did manually.

I hold ctrl on the keyboard and click on tests/test_magic.py to open it in the editor then make the test pass
I hit ctrl+c in the terminal to stop the test
I deactivate the virtual environment
```
deactivate
```
the terminal goes back to the command line
I leave the magic folder to go back to the pumping_python folder
```
cd ..
```
the terminal shows
```
...\pumping_python >
```

I want to use makePythonTdd.ps1 to make another project with a different name. I change magic to the name of the new project in the editor

Note

The lines that are changing in the code are highlighted

mkdir magic_again
cd magic_again
mkdir src
touch src/magic_again.py
mkdir tests
touch tests/__init__.py

"import unittest


class TestMagicAgain(unittest.TestCase):

    def test_failure(self):
        self.assertFalse(True)


# Exceptions Encountered
# AssertionError
" | Out-File "tests/test_magic_again.py" - Encoding UTF8

python3 -m venv .venv
source .venv/bin/activate
python3 -m pip install --upgrade pip
"pytest-watch" | Out-File requirements.txt -Encoding UTF 8
python3 -m pip install --requirement requirements.txt
pytest-watch

I run makePythonTdd.ps1 in the terminal to make a project named magic_again

./makePythonTdd.ps1

the terminal shows AssertionError

======================================= FAILURES =======================================
_____________________________ TestMagicAgain.test_failure ______________________________

self = <tests.test_magic.TestMagicAgain testMethod=test_failure>

    def test_failure(self):
>       self.assertFalse(True)
E       AssertionError: True is not false

tests/test_magic_again.py:7: AssertionError
=============================== short test summary info ================================
FAILED tests/test_magic_again.py::TestMagicAgain::test_failure - AssertionError: True is not false
================================== 1 failed in X.YZs ===================================

I make the test pass

I hit ctrl+c to exit the tests in the terminal

I run tree to see what I have in pumping_python now

tree /F

the terminal shows

.
├── magic
│   ├── .pytest_cache
│   ├── requirements.txt
│   ├── src
│   ├── tests
│   └── .venv
├── magic_again
│   ├── .pytest_cache
│   ├── requirements.txt
│   ├── src
│   ├── tests
│   └── .venv
└── makePythonTdd.sh

the program works and can reliably make a Python Test Driven Development environment the way I want it, but there is a problem

how to use a variable in a PowerShell script¶

I changed magic to magic_again in 4 places in makePythonTdd.sh. I would have to do the same change every time I have a new project, and I want to follow The Do Not Repeat Yourself (DRY) Principle. I want the program to take a project name once and use that name when making the project to make the following

the project folder
the file for the program in the src folder
the file for the test in the tests folder
the test class in the test file
the virtual environment in the .venv folder

The program should always make this structure

PROJECT_NAME
├── requirements.txt
├── src
│   └── PROJECT_NAME.py
├── tests
│   ├── __init__.py
│   └── test_PROJECT_NAME.py
└── .venv

Time to use a variable for the name of the project

I add a name to represent any project name that I give to makePythonTdd.ps1 when I want it to make a project

$PROJECT_NAME="magic_again"
mkdir magic_again
cd magic_again
mkdir src
touch src/magic_again.py
mkdir tests
touch tests/__init__.py

"import unittest


class TestMagicAgain(unittest.TestCase):

    def test_failure(self):
        self.assertFalse(True)


# Exceptions Encountered
# AssertionError
" | Out-File "tests/test_magic_again.py" - Encoding UTF8

python3 -m venv .venv
source .venv/bin/activate
python3 -m pip install --upgrade pip
"pytest-watch" | Out-File requirements.txt -Encoding UTF 8
python3 -m pip install --requirement requirements.txt
pytest-watch

a variable is a name that is used for a value that can change. For example, we use the word woman to represent any woman, man to represent any man, child to represent any child, and parent to represent anyone with a child. In this case I use $PROJECT_NAME to represent any name of a project

I change every where I have magic_again in the program, to use the variable I just added so that I only have to make a change in one place

Note

The lines that are changing in the code are highlighted

$PROJECT_NAME="magic_again"
mkdir $PROJECT_NAME
cd $PROJECT_NAME
mkdir src
touch src/$PROJECT_NAME.py
mkdir tests
touch tests/__init__.py

"import unittest


class Test$PROJECT_NAME(unittest.TestCase):

    def test_failure(self):
        self.assertFalse(True)


# Exceptions Encountered
# AssertionError
" | Out-File "tests/test_$PROJECT_NAME.py" - Encoding UTF8

python3 -m venv .venv
source .venv/bin/activate
python3 -m pip install --upgrade pip
"pytest-watch" | Out-File requirements.txt -Encoding UTF 8
python3 -m pip install --requirement requirements.txt
pytest-watch

I run the program again in the terminal

./makePythonTdd.ps1

the terminal shows

======================================= FAILURES =======================================
____________________________ Testmagic_again.test_failure ______________________________

self = <tests.test_magic.Testmagic_again testMethod=test_failure>

    def test_failure(self):
>       self.assertFalse(True)
E       AssertionError: True is not false

tests/test_magic_again.py:7: AssertionError
=============================== short test summary info ================================
FAILED tests/test_magic_again.py::Testmagic_again::test_failure - AssertionError: True is not false
================================== 1 failed in X.YZs ===================================

I change True to False in tests/test_magic_again.py to make the test pass
I hit ctrl+c in the terminal to stop the test
I deactivate the virtual environment
```
deactivate
```
the terminal goes back to the command line
I leave the magic_again folder to go back to the pumping_python folder
```
cd ..
```
the terminal shows
```
...\pumping_python
```

I run tree to see what I have in the pumping_python folder now

tree /F

the terminal shows

.
├── magic
│   ├── .pytest_cache
│   ├── requirements.txt
│   ├── src
│   ├── tests
│   └── .venv
├── magic_again
│   ├── .pytest_cache
│   ├── requirements.txt
│   ├── src
│   ├── tests
│   └── .venv
└── makePythonTdd.sh

The program works as expected, and I only need to give the project name in one place. It would be nice if I do not have to go into the file to give it the project name. I want to be able to just call the program and give it a name for the project from the command line. I can do this with $args[0] in PowerShell, it represents the first argument given when a program is called. For example,
```
command argument
```
in the code above, command will be makePythonTdd.ps1 and $args[0] will be argument or whatever name I give.

Here are a few other examples
```
mkdir name_of_folder
```
mkdir is the command, and $args[0] is name_of_folder
```
New-Item name_of_file
```
New-Item is the command, and $args[0] is name_of_file
```
echo "anything"
```
echo is the command, and $args[0] is "anything"
```
tree /F
```
tree is the command and $args[0] is /F
I change magic_again to $args[0] in makePythonTdd.ps1
```
1$PROJECT_NAME=$args[0]
```

I try the program again, this time with a different name for the project in the terminal

./makePythonTdd.ps1 more_magic

the terminal shows

======================================= FAILURES =======================================
_____________________________ Testmore_magic.test_failure ______________________________

self = <tests.test_more_magic.Testmore_magic testMethod=test_failure>

    def test_failure(self):
>       self.assertFalse(True)
E       AssertionError: True is not false

tests/test_more_magic.py:7: AssertionError
=============================== short test summary info ================================
FAILED tests/test_more_magic.py::Testmore_magic::test_failure - AssertionError: True is not false
================================== 1 failed in 0.04s ===================================

I hold ctrl on the keyboard in the terminal and click on tests/test_more_magic.py to open it in the editor, then make the test pass
I use ctrl+c on the keyboard in the terminal to stop the tests
I deactivate the virtual environment
```
deactivate
```
the terminal goes back to the command line
I leave the more_magic folder to go back to the pumping_python folder
```
cd ..
```
the terminal shows
```
...\pumping_python >
```

I run tree to see what I have in the pumping_python folder

tree /F

the terminal shows

.
├── magic
│   ├── .pytest_cache
│   ├── requirements.txt
│   ├── src
│   ├── tests
│   └── .venv
├── magic_again
│   ├── .pytest_cache
│   ├── requirements.txt
│   ├── src
│   ├── tests
│   └── .venv
├── makePythonTdd.sh
└── more_magic
    ├── .pytest_cache
    ├── requirements.txt
    ├── src
    ├── tests
    └── .venv

I can now make a Test Driven Development environment with makePythonTdd.ps1 when I give it a name for the PROJECT_NAME variable. For example, when I type this in the terminal

./makePythonTdd.ps1 assertion_error

the terminal shows

====================================== FAILURES =======================================
__________________________ Testassertion_error.test_failure ___________________________

self = <tests.test_assertion_error.Testassertion_error testMethod=test_failure>

    def test_failure(self):
>       self.assertFalse(True)
E       AssertionError: True is not false

tests/test_assertion_error.py:7: AssertionError
=============================== short test summary info ===============================
FAILED tests/test_assertion_error.py::Testassertion_error::test_failure - AssertionError: True is not false
================================== 1 failed in X.YZs ==================================

the computer makes a Test Driven Development environment for a project called assertion_error and runs the first failing test. I continue this in AssertionError

review¶

Computer Programming allows me to take some steps and make them a one line command for the computer to do for me. You have seen a way to make a Python Test Driven Development Environment, and have a program to do it for you on any Windows computer without Windows Subsystem for Linux.

How many questions can you answer after going through this chapter?

Would you like to test test AssertionError?

Click Here to see the code for the program_ to make a Python Test Driven Development environment for any Linux or MacOS computers