Testing path operations in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a test client for the FastAPI app.

FastAPI

from fastapi.testclient import TestClient
from main import app

client = [1](app)

Drag options to blanks, or click blank then click option'

AAppClient

BClient

CFastClient

DTestClient

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong class name like Client or FastClient.

Not importing TestClient before using it.

The TestClient class from fastapi.testclient is used to create a test client for the FastAPI app.

2fill in blank

medium

Complete the code to send a GET request to the '/items' path.

FastAPI

response = client.[1]('/items')

Drag options to blanks, or click blank then click option'

Aget

Bput

Cpost

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using post or put instead of get for a GET request.

Forgetting to include the path string.

To test a GET path operation, use the get method of the test client.

3fill in blank

hard

Fix the error in the assertion to check the response status code is 200.

FastAPI

assert response.status_code == [1]

Drag options to blanks, or click blank then click option'

A200

B404

C201

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Using 201 which means created, not for GET.

Using 404 which means not found.

The status code 200 means the request was successful.

4fill in blank

hard

Fill both blanks to test a POST request with JSON data and check the response status code.

FastAPI

response = client.[1]('/items', json=[2])
assert response.status_code == 201

Drag options to blanks, or click blank then click option'

Apost

Bget

C{'name': 'test item', 'price': 10.5}

D['name', 'test item']

Attempts:

3 left

💡 Hint

Common Mistakes

Using get instead of post for sending data.

Passing JSON as a list instead of a dictionary.

Use post to send data and a dictionary for JSON payload.

5fill in blank

hard

Fill all three blanks to test a PUT request updating an item and verify the response JSON content.

FastAPI

response = client.[1]('/items/1', json=[2])
assert response.status_code == 200
assert response.json() == [3]

Drag options to blanks, or click blank then click option'

Aput

B{'name': 'updated item', 'price': 15.0}

C{'id': 1, 'name': 'updated item', 'price': 15.0}

Dpost

Attempts:

3 left

💡 Hint

Common Mistakes

Using post instead of put for updating.

Not matching the response JSON with expected updated data.

Use put to update an item, send updated data as JSON, and check the returned JSON matches the updated item.

Practice

1. What is the main purpose of testing path operations in FastAPI?

easy

A. To verify that API routes respond correctly to requests

B. To improve the speed of the FastAPI server

C. To change the URL paths dynamically

D. To automatically generate API documentation

Solution

1. Step 1: Understand path operations in FastAPI

   Path operations define how the API responds to different URLs and HTTP methods.

2. Step 2: Identify the role of testing

   Testing ensures these routes work as expected by simulating requests and checking responses.

3. Final Answer:

   To verify that API routes respond correctly to requests -> Option A

4. Quick Check:

   Testing path operations = verify API routes [OK]

Hint: Testing checks if routes respond correctly to requests [OK]

Common Mistakes:

• Confusing testing with performance optimization
• Thinking testing changes URL paths
• Believing testing auto-generates docs

2. Which of the following is the correct way to import the TestClient for testing FastAPI path operations?

easy

A. from fastapi.testclient import TestClient

B. from fastapi.testing import ClientTest

C. import TestClient from fastapi

D. from fastapi.client import TestClient

Solution

1. Step 1: Recall the correct import path

   The TestClient is imported from fastapi.testclient module.

2. Step 2: Check each option

   Only from fastapi.testclient import TestClient uses the correct module and class name.

3. Final Answer:

   from fastapi.testclient import TestClient -> Option A

4. Quick Check:

   Correct import = from fastapi.testclient import TestClient [OK]

Hint: TestClient is in fastapi.testclient module [OK]

Common Mistakes:

• Using wrong module names like fastapi.client
• Swapping class and module names
• Incorrect import syntax

3. Given this FastAPI app and test code, what will be the test response status code?

from fastapi import FastAPI
from fastapi.testclient import TestClient

app = FastAPI()

@app.get('/hello')
def read_hello():
    return {'message': 'Hello World'}

client = TestClient(app)
response = client.get('/hello')

medium

A. 500

B. 404

C. 200

D. 403

Solution

1. Step 1: Analyze the defined path operation

   The app defines a GET route at '/hello' that returns a JSON message.

2. Step 2: Check the test client request

   The test client sends a GET request to '/hello', which exists, so it should succeed with status 200.

3. Final Answer:

   200 -> Option C

4. Quick Check:

   Existing route GET /hello = 200 [OK]

Hint: Existing GET route returns 200 status [OK]

Common Mistakes:

• Assuming 404 because of missing route
• Confusing status codes like 500 or 403
• Not matching HTTP method correctly

4. Identify the error in this test code snippet for a FastAPI path operation:

from fastapi import FastAPI
from fastapi.testclient import TestClient

app = FastAPI()

@app.post('/items')
def create_item(item: dict):
    return item

client = TestClient(app)
response = client.get('/items')
print(response.status_code)

medium

A. Missing import for dict type

B. Using GET method instead of POST for /items

C. Incorrect function name create_item

D. TestClient should be created after response

Solution

1. Step 1: Check the path operation method

   The route '/items' accepts POST requests only.

2. Step 2: Check the test client request method

   The test client sends a GET request to '/items', which is not allowed, causing a 405 error.

3. Final Answer:

   Using GET method instead of POST for /items -> Option B

4. Quick Check:

   Method mismatch causes error = Using GET method instead of POST for /items [OK]

Hint: Match test request method with route method [OK]

Common Mistakes:

• Using wrong HTTP method in test
• Thinking function name affects routing
• Misunderstanding import requirements
• Creating TestClient after request

5. You want to test a FastAPI path operation that returns a list of users. Which approach correctly tests that the response contains exactly 3 users with names 'Alice', 'Bob', and 'Carol'?

hard

A. Check only the response status code is 200 without inspecting data

B. Send POST request with user data and check status code 201

C. Call the path operation function directly without TestClient

D. Use TestClient to GET the route, then assert response.json() == [{'name': 'Alice'}, {'name': 'Bob'}, {'name': 'Carol'}]

Solution

1. Step 1: Understand the goal of testing response data

   We want to confirm the API returns exactly the expected list of users.

2. Step 2: Choose the correct testing method

   Using TestClient to send a GET request and asserting the JSON response matches the expected list is correct.

3. Final Answer:

   Use TestClient to GET the route, then assert response.json() == [{'name': 'Alice'}, {'name': 'Bob'}, {'name': 'Carol'}] -> Option D

4. Quick Check:

   Test response data equality = Use TestClient to GET the route, then assert response.json() == [{'name': 'Alice'}, {'name': 'Bob'}, {'name': 'Carol'}] [OK]

Hint: Assert response.json() matches expected list exactly [OK]

Common Mistakes:

• Testing with POST instead of GET for retrieval
• Calling path function directly misses request context
• Ignoring response data content in tests