Coverage reporting in Flask - Mini Project: Build & Apply

Coverage Reporting in Flask

📖 Scenario: You are building a small Flask web application and want to check how much of your code is tested by your tests. This helps you find parts of your code that need more testing.

🎯 Goal: Create a Flask app, set up coverage configuration, run tests with coverage, and generate a coverage report.

📋 What You'll Learn

Create a simple Flask app with one route

Add a configuration variable to enable testing mode

Write a test function to test the route

Run coverage to measure test coverage and generate a report

💡 Why This Matters

🌍 Real World

Coverage reporting helps developers see which parts of their web app are tested and which are not, improving code quality.

💼 Career

Understanding coverage reporting is important for software developers and testers to ensure reliable and maintainable code.

1

Create a simple Flask app

Create a Flask app by writing from flask import Flask and then create an app variable with app = Flask(__name__). Add a route / that returns the string 'Hello, Coverage!'.

Flask

from flask import Flask

# Create the Flask app
# Your code here

Need a hint?

Use Flask(__name__) to create the app and @app.route('/') to define the home page.

2

Add testing configuration

Add a configuration variable app.config['TESTING'] = True to enable testing mode in the Flask app.

Flask

from flask import Flask

app = Flask(__name__)

# Enable testing mode
# Your code here

@app.route('/')
def home():
    return 'Hello, Coverage!'

Need a hint?

Set app.config['TESTING'] = True right after creating the app.

3

Write a test function for the route

Write a test function called test_home that uses the Flask test client to send a GET request to '/' and asserts the response data equals b'Hello, Coverage!'.

Flask

from flask import Flask

app = Flask(__name__)
app.config['TESTING'] = True

@app.route('/')
def home():
    return 'Hello, Coverage!'

# Write test function here
# Your code here

Need a hint?

Use app.test_client() to create a client and send a GET request to '/'.

4

Run coverage and generate report

Add the code to run coverage by importing coverage, starting coverage with cov = coverage.Coverage() and cov.start(), then run the test function test_home(), stop coverage with cov.stop(), save coverage data with cov.save(), and finally generate a report with cov.report().

Flask

from flask import Flask
import coverage

app = Flask(__name__)
app.config['TESTING'] = True

@app.route('/')
def home():
    return 'Hello, Coverage!'

def test_home():
    with app.test_client() as client:
        response = client.get('/')
        assert response.data == b'Hello, Coverage!'

# Start coverage, run test, stop coverage, save and report
# Your code here

Need a hint?

Use the coverage module to measure coverage around the test function call.