Book Image

Mastering Flask Web Development - Second Edition

By : Daniel Gaspar, Jack Stouffer
Book Image

Mastering Flask Web Development - Second Edition

By: Daniel Gaspar, Jack Stouffer

Overview of this book

Flask is a popular Python framework known for its lightweight and modular design. Mastering Flask Web Development will take you on a complete tour of the Flask environment and teach you how to build a production-ready application. You'll begin by learning about the installation of Flask and basic concepts such as MVC and accessing a database using an ORM. You will learn how to structure your application so that it can scale to any size with the help of Flask Blueprints. You'll then learn how to use Jinja2 templates with a high level of expertise. You will also learn how to develop with SQL or NoSQL databases, and how to develop REST APIs and JWT authentication. Next, you'll move on to build role-based access security and authentication using LDAP, OAuth, OpenID, and database. Also learn how to create asynchronous tasks that can scale to any load using Celery and RabbitMQ or Redis. You will also be introduced to a wide range of Flask extensions to leverage technologies such as cache, localization, and debugging. You will learn how to build your own Flask extensions, how to write tests, and how to get test coverage reports. Finally, you will learn how to deploy your application on Heroku and AWS using various technologies, such as Docker, CloudFormation, and Elastic Beanstalk, and will also learn how to develop Jenkins pipelines to build, test, and deploy applications.
Table of Contents (15 chapters)

How does testing work?

Let's start with a very simple Python function for us to test:

def square(x): 
    return x * x 

In order to verify the correctness of this code, we pass a value, and will test if the result of the function is what we expect. For example, we could give it an input of 5, and would expect the result to be 25.

To illustrate the concept, we can manually test this function in the command line using the assert statement. The assert statement in Python simply says that if the conditional statement after the assert keyword returns False, then it will throw an exception as follows:

    $ python
    >>> def square(x): 
    ...     return x * x
    >>> assert square(5) == 25
    >>> assert square(7) == 49
    >>> assert square(10) == 100
    >>> assert square(10) == 0
    Traceback (most recent call last):
      File...