Efficient Tools for Generating Mockserver From OpenAPI Spec and Tracking Changes

Building an application with an undeveloped external API can be challenging. However, HTTP mocking tools can alleviate this pain point and simplify the development and testing process.

A mock server uses fake responses to imitate a real server, enabling parallel development and early-stage testing. It allows developers to test API-consuming components before the actual backend is ready and provides faster feedback for improvement.

There are quite a few benefits of having a mockserver:

• Enables parallel development of frontend and backend components.
• Facilitates early-stage testing without reliance on a fully functional backend.
• Provides faster feedback from internal and external users during development.
• Enhances the efficiency of the development process.

However, Mocking a REST server requires a significant time investment, not only to create the server but also to update it with changes coming from your real backend. In this article, I will share some of the tools that can help with this process. 

SwaggerHub

SwaggerHub provides a mock server for OpenAPI 2.0 and 3.0 specs. Mocking is supported on both free and paid plans.

To use the mock server, import your spec into SwaggerHub and enable "API Auto Mocking." Mock responses can be JSON, YAML, and XML and are generated based on your response schemas and the example, default, and enum values defined in the schemas.

Postman

Postman is a popular API development and testing tool that also supports generating mock APIs from OpenAPI specifications. In addition, Postman offers a simple UI that makes it easy to create, test, and share your mock APIs with others.

Creating a mock server in Postman is easy and can be done within the tool itself. In addition, they provide a handy guide explaining how to set up a mock server based on your API collection (or even from scratch) in just a few minutes. 

Additionally, you can use environment variables to make the mock server dynamic to test different response conditions easily.

Postman also provides features to share mock servers with other team members or stakeholders, making it easier for everyone to collaborate on testing and development. In addition, with the ability to monitor usage and see who is accessing your mock server, you can get valuable insights into who is using your API and how.

APIGit

APIGit is a collaborative platform that distinguishes itself with its native support for Git, providing full Git functionality to simplify the API development process and support version control. This platform enables users to effortlessly design, document, mock, test, and share APIs with ease.

APIGit offers an advanced, programmable mock server with stateful capabilities with:

• One-click generation of ready-to-use mockservers from API specifications stored in APIGit's repository.
• Easy identification of changes and updates with the "Sync Routes from API Specification" function.
• Effortless comparison and application of changes with the diff feature.

The fact that APIGit implements Git server functionality means that it supports the publishing of multiple versions of Mockserver at the same time. This is particularly useful for teams working on large-scale API projects, as it provides a flexible and scalable solution to their needs.

Stoplight

Stoplight is a platform for API design and development that includes a feature for generating a mock server. The mock server in Stoplight can be automatically generated from an OpenAPI specification, providing developers with a fast and simple way to create a simulated version of their API. For example, with Prism, Stoplight's open-source HTTP mock server, you can run fully functional fake API servers directly from an OpenAPI specification or Postman file. 

Stoplight provides two types of fake responses: 

1. Static: Useful for testing a specific request against a specific static JSON response. 
2. Dynamic: Generate a random fake JSON response based on the schema from your API specification file.

Happy mocking!