NestJS
Guards, interceptors, pipes, and exception filters are the middleware layer of NestJS. They run before and after your controllers but are often left untested. This guide shows how to unit test each one in isolation using ExecutionContext mocks, and how to test their integration behavior via e2e tests with Supertest.
Testing
Testing NestJS microservices is harder than testing monolithic HTTP apps because you now have distributed components, message brokers, and transport-specific behavior to deal with. The test strategy depends on what you're testing: the message handler logic itself, the transport serialization, or the end-to-end flow across
Testing
Unit testing in NestJS is not complicated, but it does require understanding how the framework's dependency injection container works. Once you get that, writing fast, isolated tests for services, controllers, and providers becomes straightforward. This guide walks through the real mechanics — no hand-waving. How NestJS Testing Works
Testing
End-to-end tests for NestJS apps test the full HTTP stack — routing, guards, pipes, middleware, serialization — without deploying to a server. You boot your actual NestJS application inside the test process, send real HTTP requests against it, and assert on real HTTP responses. No mocks, no shortcuts. This guide
Testing
Testing GraphQL APIs in NestJS requires a different approach than REST. The entry point is always POST /graphql, the response is always 200 OK (even for errors), and you need to think about resolvers, subscriptions, schema validation, and the N+1 problem. This guide covers all of it. Testing Resolvers
Testing
NestJS comes with Jest pre-configured and a full testing module built into the framework. Most teams generate the boilerplate, delete the placeholder it('should be defined') tests, and ship anyway. The testing infrastructure is already there. Here's how to actually use it. NestJS Testing Architecture