How to Use VSCode for API Testing Without Postman

When it comes to API development, testing is a crucial step in ensuring the endpoints and functionality work as expected. Postman has long been a go-to tool for developers when testing APIs. However, if you’re already working within Visual Studio Code (VSCode), wouldn’t it be great if you could streamline the process and test APIs directly there? The good news is—you can. VSCode, with its robust ecosystem of extensions, can serve as a powerful tool for API testing, eliminating the need for external tools like Postman.

This guide will walk you through how to use VSCode to test your APIs, organize requests, and review responses without relying on Postman. By the end, you'll have everything you need for effective API testing all within your favorite code editor.

Before we get started, let’s introduce an alternative extension called APIDog, which serves as another powerful Postman alternative.

APIDog is a VSCode extension designed to simplify API testing by offering a feature-rich, yet lightweight solution directly within your editor. Like REST Client, APIDog allows you to send requests, manage environments, and analyze responses. It provides a balance between raw, script-based testing and the convenience of a graphical interface, making it accessible for both beginners and advanced users alike. While this guide primarily focuses on using the REST Client extension, it’s worth exploring APIDog as an option if you’re looking for slightly different functionality or a more intuitive environment that still integrates seamlessly into VSCode.

https://apidog.com/

Why Use VSCode Instead of Postman?

Although Postman is a fantastic tool for API testing, integrating this functionality into VSCode offers several advantages:

Streamlined Workflow: Staying within the VSCode environment means you won't need to switch back and forth between tools.
Customization: VSCode is highly customizable. It allows you to tailor the API testing process to your preferences and needs.
Reduced Resource Usage: Postman, while feature-rich, can be resource-intensive. With VSCode, you operate in a lighter environment.
Built-in Version Control: Because you'll be saving API requests and testing scripts as files, you'll naturally benefit from Git integration available in VSCode.

Now, let’s dive into how you can set up your VSCode environment for API testing.

Prerequisites

Before we start, ensure you meet the following prerequisites:

VSCode Installed: Download and install VSCode if you haven’t already.
Basic Knowledge of APIs: Understanding how REST or GraphQL APIs work is helpful.
Node.js Installed (optional): While not mandatory, certain extensions and scripts may require Node.js for executing JavaScript-based code.

Next, we’ll install some necessary extensions.

Installing Required Extensions

To transform VSCode into an API testing tool, you’ll need a couple of extensions. Fortunately, these tools are free and readily available in the VSCode marketplace.

1. REST Client

The REST Client extension by Huachao Mao is the star of this guide. It allows you to send HTTP requests directly from within VSCode and view responses. Here’s how to install it:

Open VSCode.
Navigate to the Extensions tab (Ctrl+Shift+X or Cmd+Shift+X on Mac).
Search for REST Client.
Click Install.

This extension enables you to write HTTP request files (.http or .rest) and execute them within VSCode.

2. Thunder Client (Optional)

For a more graphical experience, you can install Thunder Client. This extension provides an interface similar to Postman but remains embedded within VSCode. To install:

Search for Thunder Client in the Extensions tab.
Click Install.

While Thunder Client is optional for those who prefer a graphical UI, the REST Client extension is our primary focus in this guide.

Writing API Requests Using REST Client

With the REST Client installed, you can start writing API requests. These requests are saved in .http or .rest files, allowing you to organize them within your project.

Creating a Request File

Create a new file in your project and save it with a .http extension, e.g., api-tests.http.
Open the file and begin writing your API requests.

Here’s an example of a simple GET request:

GET https://jsonplaceholder.typicode.com/posts HTTP/1.1

Once you’ve written your request, you’ll notice a Send Request button above the line. Clicking it will execute the request, and the response will appear in a new tab within VSCode.

Common HTTP Methods for API Testing

Let’s explore how to write different types of requests in .http files.

1. GET Request

GET requests are used to retrieve data. Here’s an example of a GET request:

GET https://api.example.com/users HTTP/1.1
Authorization: Bearer your-token-here

This GET request fetches a list of users. Include headers like Authorization for authentication if the API requires it.

2. POST Request

POST requests are used to send data to the server. Here’s how to write one:

POST https://api.example.com/users HTTP/1.1
Content-Type: application/json

{
    "name": "John Doe",
    "email": "johndoe@example.com"
}

In a POST request, you typically include a JSON payload after the headers. The Content-Type header ensures the server knows you're sending JSON data.

3. PUT Request

PUT requests are used to update data. For example:

PUT https://api.example.com/users/1 HTTP/1.1
Content-Type: application/json

{
    "name": "John Doe Updated",
    "email": "updatedemail@example.com"
}

This request updates the user with ID 1.

4. DELETE Request

DELETE requests remove data from the server:

DELETE https://api.example.com/users/1 HTTP/1.1
Authorization: Bearer your-token-here

This request deletes the user with ID 1.

5. Including Query Parameters

To include query parameters in your requests, append them to the URL:

GET https://api.example.com/users?role=admin&page=2 HTTP/1.1

Query parameters help filter or paginate data.

Organizing and Using Variables in Requests

When testing APIs, you often need to reuse the same values, such as API endpoints or authentication tokens. The REST Client extension allows you to define variables to make your tests more maintainable.

Defining Variables

You can define variables in a file named .env or directly within your request file. For example:

In a .env file:

baseUrl=https://api.example.com
authToken=your-auth-token

In your .http file:

@baseUrl = https://api.example.com
@authToken = your-auth-token

Using Variables in Requests

Once your variables are defined, you can reference them in your requests:

GET {{baseUrl}}/users HTTP/1.1
Authorization: Bearer {{authToken}}

This dynamic approach simplifies updates and ensures consistency across your tests.

Viewing and Analyzing Responses

After executing a request, the response appears in a new tab within VSCode. The REST Client extension provides the following information:

Response Body: Displays the data returned by the API (e.g., JSON, HTML).
Response Headers: Shows metadata such as the status code or content type.
Response Time: Indicates how quickly the API responded.
Response Size: Shows the total size of the response.

This detailed feedback allows you to analyze the behavior of your APIs and debug issues effectively.

Advanced Features of REST Client

Here are some advanced features of the REST Client extension that make it even more powerful:

1. Chaining Requests

You can define requests in sequence and reuse responses between them. For example:

POST https://api.example.com/auth/login HTTP/1.1
Content-Type: application/json

{
    "username": "testuser",
    "password": "mypassword"
}

GET https://api.example.com/users HTTP/1.1
Authorization: Bearer {{login.response.body.token}}

This chain uses the token from the login response in subsequent requests.

2. Saving Responses

You can save API responses for future reference. Add the following comment to your request:

// @response save <filename>

The response will automatically be saved as a file in your project directory.

3. Send Request with Shortcut

Instead of clicking the Send Request button, you can use a shortcut. Press Ctrl+Alt+R or Cmd+Alt+R to execute the request.

Thunder Client: An Alternative for Postman-Like Experience

If you prefer a graphical interface similar to Postman, Thunder Client offers a great alternative. After installing the extension, an icon will appear in the Activity Bar. From there, you can:

Create new requests.
Add headers, query parameters, and payloads.
Organize requests into collections.

Thunder Client is beginner-friendly, but it doesn’t offer the same flexibility as REST Client for advanced users.

Tips for Effective API Testing in VSCode

Use Version Control: Save your .http files in your project repository for easy tracking.
Organize Requests: Group related API requests into dedicated files or folders for better organization.
Automate with Scripts: For large-scale testing, consider writing automation scripts in Node.js using libraries like Axios or Fetch.
Use Workspace Settings: Configure VSCode workspace settings to customize the API testing experience further.

Wrapping Up

Visual Studio Code is more than just a code editor; it’s a versatile platform that can significantly enhance your API testing workflow. With the REST Client extension, you can send requests, analyze responses, and manage your API tests without ever leaving the VSCode environment. For those who prefer a graphical interface, Thunder Client offers a fantastic alternative.

By integrating API testing into VSCode, you save time, resources, and avoid the hassle of switching between tools. Whether you're a hobbyist or a professional developer, using VSCode for API testing is a streamlined, efficient, and effective approach.

So, go ahead—ditch Postman and maximize the potential of VSCode for your API testing needs!