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🧪 Test Your First Endpoint

Before you deploy anything into production, it's crucial to simulate how your API will respond in both expected and unexpected situations. The foundation of that process starts with testing endpoints

, which act as the building blocks of all interactions between client and server.

Endpoints represent not just routes, but contracts—defining exactly what input they accept, what output they provide, and what types of responses (success or failure) they produce. In this section, you’ll learn how to test live endpoints using Swagger and Redoc; simulate edge cases and invalid requests; and confirm whether your OpenAPI spec

matches the actual behavior of your mock or live server.

🛰️ What Is an API Endpoint Really?​

GET Request Example
1get:
2summary: Get all users
3responses:
4  '200':
5    description: A list of users

An endpoint, conceptually, is a touchpoint between your consumer and your server logic. In a RESTful API, endpoints are mapped to logical resources such as /users, /posts, or /payments; each resource is then manipulated through verbs like GET, POST, PATCH, or DELETE.

For example, GET /users retrieves a list of users; POST /users adds a new user; DELETE /users/:id removes a specific user.

What matters most is that these are not just arbitrary URLs; they are documented, versioned, and expected to behave predictably. Their responses, error codes, and accepted parameters are defined in your YAML and enforced by validators or mock servers. This makes API endpoints both contractual and testable.

⚙️ Swagger Try It Out: Live Request Simulation​

💡 Note: Make sure your local server (e.g., Mockoon) is running at http://localhost:3000 for the Try It Out feature to work properly.
Figure 1. Swagger UI testbed for sending mock requests

With your mock server

running via Mockoon, Swagger allows you to execute requests directly from the browser.

Try these: GET /users to pull live mock data; POST /users to simulate adding new entries; use invalid formats to trigger errors intentionally.

POST Body Example
1requestBody:
2content:
3  application/json:
4    schema:
5      type: object
6      required:
7        - name
8        - email
9      properties:
10        name:
11          type: string
12        email:
13          type: string

Swagger’s Try It Out

feature provides real-time feedback for both successful and failing requests, helping confirm that your request schema, required fields, and response codes behave as documented.

🧯 Simulate Errors, Invalid Requests, and Edge Conditions​

To build a reliable API, it’s essential to simulate how things behave when they go wrong. Using Swagger, Postman, or curl, try submitting incomplete JSON payloads, unauthorized tokens, or malformed requests. Doing this allows you to confirm that your API returns appropriate status codes, such as: 400 for malformed input; 401 for missing auth headers; 500 for internal logic failures.

Error Response Example
1responses:
2'400':
3  description: Missing required field
4'500':
5  description: Internal server error

When your YAML accurately reflects these conditions, your frontend and partner teams can design their error handling and retries with confidence.

📘 Redoc Snapshot View​

🧪 Launch Full Redoc Viewer

Click to explore the full API spec using Redoc

Figure 2. Redoc snapshot reference overview

Redoc focuses on documentation clarity rather than interaction. Use it to review schema structure, enum types, and required vs optional fields; share a source of truth with clients or devs; and navigate the contract without needing to run live requests.

This static overview is commonly used in security reviews, audits, onboarding materials, and QA handoffs—helping teams align around what's been documented versus what’s been implemented.

✅ Summary & What's Next​

You now understand what API endpoints are, how to run basic and advanced test cases using Swagger and Redoc, and how to simulate failures that ensure your YAML spec is robust. These tools help enforce the contract between teams and ensure predictable integration behavior.

This chapter covered: live request simulation using Swagger; error handling via malformed or invalid payloads; static schema review and contract sharing with Redoc.

In the next section, we’ll take a deeper look at HTTP status codes

—how to interpret them, map them to your endpoints, and return custom messages based on context.

👉 Ready to continue? Jump to Understanding HTTP Status Codes.