Testing routes and responses in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the response status code for a successful GET request?

Consider a Flask route that returns a simple message with status code 200. What status code will the test client receive when making a GET request to this route?

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/hello')
def hello():
    return 'Hello, world!', 200

with app.test_client() as client:
    response = client.get('/hello')
    status_code = response.status_code

A 302

B 404

C 500

D 200

💡 Hint

Think about the HTTP status code for a successful request.

A status code of 200 means the request was successful and the server returned the expected response.

📝 Syntax

intermediate

Which option correctly tests a POST route with JSON data?

You want to test a Flask POST route that accepts JSON data. Which test client call is correct?

Flask

from flask import Flask, request, jsonify
app = Flask(__name__)

@app.route('/data', methods=['POST'])
def data():
    json_data = request.get_json()
    return jsonify(received=json_data), 201

with app.test_client() as client:
    response = client.post('/data', json={'key': 'value'})
    status_code = response.status_code

A client.post('/data', json={'key': 'value'})

B client.post('/data', data='key=value')

C client.post('/data', content_type='application/json')

D client.post('/data', data={'key': 'value'})

💡 Hint

Use the test client method that automatically sets JSON headers and serializes data.

Using json= in client.post sends JSON data with the correct content type.

🔧 Debug

advanced

Why does this test fail with a 405 Method Not Allowed error?

Given this Flask route and test, why does the test fail with a 405 error?

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/item', methods=['GET'])
def get_item():
    return 'Item details'

with app.test_client() as client:
    response = client.post('/item')
    status_code = response.status_code

A The route is missing a POST method handler.

B The test client is not properly initialized.

C The route only allows GET requests, but the test uses POST.

D The route URL is incorrect.

💡 Hint

Check the allowed HTTP methods for the route.

The route only accepts GET requests. Sending a POST request causes a 405 Method Not Allowed error.

❓ state_output

advanced

What is the value of response.json after this test?

A Flask route returns JSON data. What will the test client receive in response.json?

Flask

from flask import Flask, jsonify
app = Flask(__name__)

@app.route('/info')
def info():
    return jsonify(name='Alice', age=30)

with app.test_client() as client:
    response = client.get('/info')
    data = response.json

A null

B {'name': 'Alice', 'age': 30}

C {'name': 'Alice'}

D {'name': 'Alice', 'age': '30'}

💡 Hint

Check the JSON keys and value types returned by the route.

The route returns a JSON object with keys 'name' and 'age' where age is an integer 30.

🧠 Conceptual

expert

Which statement about Flask test client context is true?

When using Flask's test client in a with-statement, which is correct about the application context?

A The application context is automatically pushed and popped inside the with-statement.

B You must manually push the application context before using the test client.

C The test client does not manage any context; you must handle it yourself.

D The test client disables the application context during tests.

💡 Hint

Think about how Flask manages contexts during testing.

Using the test client as a context manager automatically pushes and pops the application context, simplifying tests.