TOOL UP YOUR API INTEGRATION TESTING WITH OPENAPI
By Vinod Chandru
The modern web application is no longer a self-contained hub for the distribution of its own data. Once repositories of their own unique resources, web apps have become a mesh of internal and external data and other information, all carefully intertwined and relying on one another to fulfill their purposes. Applications, both software and hardware, increasingly rely on external APIs to pipe data into their own APIs before being referenced, mutated, or checked against, ultimately providing the application's users with what they seek.
What is the OpenAPI Spec?
The OpenAPI Specification, formerly known as Swagger, defines a standard, language-agnostic interface to RESTful APIs. The interface allows humans and computers to discover and understand the capabilities of an API without access to source code or documentation.
It provides a handful of other companion tools to better help test and provide users with a deeper look into an API and its details. The Swagger UI automatically generates documentation that will accept parameters and then return responses from the API based on the rules outlined in the OpenAPI Specification itself. For its part, the Swagger Editor provides a browser-based editor where a developer can write OpenAPI specs and generate documentation in real time. Both the editor and the UI tools help users ingest an API more easily, and provide interactive docs in a clickable, simple-to-use interface. These docs allow you to see and test examples of each endpoint's response without writing a single line of code. But the OpenAPI Specification is also used by engineers as a powerful tool for the internal testing of APIs in applications—especially APIs that rely on third-party integrations prone to encounter problems that are out of a developer’s control.
Contract testing
Contract testing integrates OpenAPI specs directly into your internal testing processes. At a basic level, contract testing verifies that an API's responses match the "contract" specified in an OpenAPI specification. This means making sure that responses contain all of the required properties, or that requests return the correct status codes upon completion.
In contract testing, an endpoint's response is tested to make sure it abides by the rules and guidelines defined inside of an OpenAPI specification. The testing results in either a passing or failing grade, similar to traditional continuous integration tests before deployment of an application's build.