This version illustrates Test Driven Development (TDD) and the use of decorator functions to extend functionality and code reuse to remove duplication.

TDD Simplified

The Test Driven Development Cycle

User Model

A Simple User model

We are going to start with a simple User Model so that we can fully grasp and appreciate the TDD workflow

End Points Sequence Diagrams

Get Users: GET `/users`

Get a User: GET `/users/<user_id>`

Create a User: POST `/users`

Update a User: PUT `/users`

Delete a User: DELETE `/users/<user_id>`

Dependencies

How to set up and run the project

Create and Activate a Python virtual environment
Install requirements
```
pip install -r requirements.txt 
```
Set environment variables specified in the env_sample.txt
- DATABASE_URL for Production
- DEV_DATABASE_URL for Development
- TEST_DATABASE_URL for Testing
  
  Remember to create separate databases for testing and running the code
Update the migrations
```
flask db upgrade
```
Run the project
```
python -m run
```

How to Create and Activate a Python virtual Environment

Open your terminal at the root of the project
create a virtual environment
```
python -m venv env
```
Activate the virtual environment
- for windows
```
env\Scripts\activate
```
- for linux\macOS
```
source env/bin/activate
```
Deactivate the virtual environment
```
deactivate
```

How to run tests

Activate the virtual environment
Create you test database
SET the TEST_DATABASE_URL environment variable
Run the tests using pytest
```
  pytest tests
```

Important to know

how to get json data from the request object

{
  "username": "Arthur"
}

json returns
a python dictionary with key-value pairs
- The parsed JSON data
  if mimetypeindicates
  JSON (*application/json)is_json)
  .
- Calls get_json()with
  default arguments.
- If the request content type is not application/json, this will raise a 400 Bad Request error.
```
data = request.json
username = data["username"]
```
get_json(force=False, silent=False, _
cache=True_) returns
a dict with key-value pairs
- Raises a 400 error if the content type is incorrect.
- force (bool) – Ignore the mimetype and always try
  to parse JSON.
```
data = request.get_json(force=True)
```
flask.json.loads(s, app=None, **
kwargs)
- Serialize an object to a string of JSON.
```
data = json.loads(request.data.decode())
```

How to convert to python objects to JSON String

flask.json.jsonify
- Serialize data to JSON and wrap it in a Response with the application/json mimetype
```
jsonify({"username": "Arthur"})
```
flask.json.dumps(obj, app=None, **
kwargs)
- Serialize an object to a string of JSON.
```
user_dict = { "username": "Arthur" }
json_data = json.dumps(user_dict)
```

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version one

TDD Simplified

The Test Driven Development Cycle