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Automation Testing with Pytest

Posted by

Akshay Singla on 24 Nov 2023

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Testing is critical to software development, ensuring the code works as intended and providing confidence in its reliability. Python, a versatile and popular programming language, offers several testing frameworks. One such framework is Pytest, which stands out for its simplicity, scalability, and ease of use. In this blog post, we’ll explore the advantages of using Pytest for testing Python code and guide you through the basics of getting started.

 

Why Pytest?

A variety of test frameworks are available in the market, each with its own pros and cons. The benefits of using Pytest framework over other test frameworks include:

  1. Ease of Use: Pytest’s minimalist and intuitive approach makes it easy for beginners and experienced developers to write tests. Its simple syntax requires minimal boilerplate code, reducing the effort to set up and maintain test cases.
  2. Powerful Assertions: Pytest comes with a rich set of built-in assertion methods, making it straightforward to validate the expected behavior of your code. These assertions provide clear failure messages, aiding in troubleshooting and bug fixing.
  3. Test Discovery: Pytest automatically discovers and runs all test modules and functions within the project directory structure. It saves time and effort by eliminating the need to specify test files or test cases to execute explicitly.
  4. Fixtures: Fixture is a powerful feature of Pytest that simplifies the setup and teardown of test resources. Fixtures provide a clean and reusable way to initialize and clean up the required data or dependencies for tests. They can be shared across test cases, modules, or even entire test suites, enhancing code reusability and reducing duplication.

 

Getting Started with Pytest

If you are new to Pytest, the following steps can help you install and begin testing:

Step 1 – Installation

Install Pytest using pip, the package manager for Python. Open the terminal or command prompt and run the below command:

 

pip install pytest

 

Step 2 – Writing Tests

Create a new Python file whose name begins with “test_” to indicate that it contains test code. Import the necessary modules and write your test functions. Each test function should start with “test_” to ensure Pytest recognizes it as a test case.

 

import pytest 

 

def test_addition(): 

assert 2 + 2 == 4 

 

def test_subtraction(): 

assert 5 – 3 == 2

 

Step 3 – Running Test

To execute your tests, navigate to the project directory in your terminal and run the following command:

 

pytest

 

Pytest will automatically discover and execute all test functions within the project directory and display the results.

 

Advanced Features

Pytest has a variety of features beyond Fixtures that we have already discussed under the benefits of the test framework. Below are some advanced features of Pytest:

  • Test Coverage: Pytest integrates seamlessly with coverage tools like pytest-cov, allowing you to measure the code coverage of your tests. This helps identify areas of your code that lack test coverage, ensuring a higher level of confidence in the quality of your software.
  • Parametrized Testing: The test framework supports parameterizing test functions using decorators or fixtures. This feature allows you to write a single test function that executes multiple times with different input values, reducing code duplication and enhancing test readability.
  • Test Doubles: Pytest provides built-in support for creating test doubles such as mocks, stubs, and spies using the pytest-mock plugin. Test doubles help isolate code under test and enable controlled interactions with external dependencies.

 

What is API Automation Testing?

Now that we are familiar with Pyest let’s try to understand API Automation Testing.

APIs serve as the building blocks of modern software applications, enabling different components to communicate and interact seamlessly. API automation testing involves the creation of scripts and frameworks to automate the testing of these APIs. It focuses on verifying the functionality, reliability, security, and performance of APIs without the need for manual intervention.

 

Differences from Other Testing Types

API automation testing differs from other testing types, such as unit testing and UI testing, in several ways:

  • Unit Testing: Unit testing focuses on testing individual components or functions in isolation. It ensures that each component works as intended. On the other hand, API testing involves testing the interaction between different components and their integration.
  • UI Testing: UI testing concentrates on the graphical user interface of an application. It ensures that user interactions with the interface produce the expected results. API testing, however, operates at a lower level, examining the underlying functionality and data exchange between components.

 

Importance of API Automation Testing

API automation testing holds immense importance due to several key reasons:

  • Faster Feedback: Automated tests can be executed rapidly and repeatedly. Developers receive prompt feedback on the integration and functionality of APIs, allowing them to identify and rectify issues early in the development cycle.
  • Enhanced Test Coverage: API automation tests can cover a vast range of scenarios and edge cases that might be difficult to replicate manually. This improves the overall coverage of test cases and ensures more comprehensive testing.
  • Regression Testing Made Easier: As software evolves, it is crucial to ensure that new changes do not break existing functionalities. Automated API tests excel at regression testing, ensuring that modifications don’t adversely affect the existing codebase.
  • Consistency and Accuracy: Manual testing is prone to human errors, whereas automated tests execute the same steps consistently and accurately every time, which reduces the likelihood of overlooking critical issues.
  • Resource and Cost Efficiency: While API automation testing requires an initial investment of time and effort, it significantly reduces the need for ongoing manual testing, leading to substantial long-term savings in resources and costs.

 

Benefits of Automating API Tests

Below are the benefits of employing automated API tests:

  • Faster Feedback Loops: Rapid execution of automated tests leads to quicker identification and resolution of issues, accelerating the development cycle.
  • Improved Test Coverage: Automated tests can cover a wide range of scenarios, ensuring thorough testing even for complex systems.
  • Efficient Regression Testing: Automated tests are well-suited for repetitive regression testing, ensuring that new updates don’t break existing features.
  • Early Bug Detection: Automated tests catch bugs early, preventing them from propagating to later stages of development.
  • Parallel Testing: Multiple tests can be executed simultaneously, saving time and expediting testing processes.
  • Continuous Integration and Continuous Deployment (CI/CD): Automated API tests seamlessly integrate with CI/CD pipelines, providing confidence in deploying changes frequently and reliably.

 

Here is an example to showcase API Testing using Pytest

import pytest

import requests

 

@pytest.fixture

def base_url():

    return “https://api.example.com”  # Replace with your API base URL

 

def test_get_user(base_url):

    response = requests.get(f”{base_url}/users/1″)

    assert response.status_code == 200

    user = response.json()

    assert user[“id”] == 1

    assert user[“name”] == “John Doe”

 

def test_create_user(base_url):

    data = {

        “name”: “Jane Smith”,

        “email”: “[email protected]

    }

    response = requests.post(f”{base_url}/users”, json=data)

    assert response.status_code == 201

    created_user = response.json()

    assert created_user[“name”] == “Jane Smith”

    assert created_user[“email”] == “[email protected]

 

Explanation of Code

Here is how the above code helps us with testing:

  • We start by importing the necessary libraries: pytest for test assertions and fixtures, and requests for making HTTP requests to the API.
  • The base_url fixture returns the base URL of the API under test. You can modify it according to your API’s URL.
  • The test_get_user function is a test case that verifies the behavior of the API endpoint for retrieving a user with ID 1. It sends a GET request to the /users/1 endpoint and asserts that the response status code is 200 (indicating success). It also checks the values of the returned user object.
  • The test_create_user function is another test case that verifies the behavior of the API endpoint for creating a user. It sends a POST request to the /users endpoint with a JSON payload containing the user’s name and email. It asserts that the response status code is 201 (indicating successful creation) and verifies the values of the created user object.

To run these tests, simply execute the following command in your terminal:

pytest

 

Pytest will automatically discover and execute all the test functions prefixed with test_ in the current directory and its subdirectories.

 

Conclusion

Pytest is a powerful and user-friendly testing framework for Python that simplifies the process of writing and executing tests. Its simplicity, powerful assertions, and robust fixture system make it an excellent choice for small- and large-scale projects. By adopting Pytest, you can streamline your testing workflow, improve code quality, and gain confidence in the reliability of your software. So, try Pytest and experience the joy of testing with Python.

Remember, testing is not just a one-time task but an ongoing process throughout the development. To learn more about Pytest, contact our Quality Engineering & Testing experts.



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