What tools or methods are used to test API functionality?

API functionality testing is usually carried out using the following tools:

• Manual testing tools: Postman, Insomnia — allow sending requests and analyzing responses.
• Automated testing frameworks: pytest (Python), JUnit (Java), RestAssured, SoapUI — for writing and executing tests.
• Load testing tools: JMeter, Gatling — check API performance.

Tests verify:

• Correctness of responses (status codes, response body).
• Validation of input data.
• Error handling.
• Authorization and authentication.

An example of a simple test in Python using requests and pytest:

import requests

def test_get_user():
    response = requests.get("https://api.example.com/users/1")
    assert response.status_code == 200
    data = response.json()
    assert data["id"] == 1