Suites – modern unit tests framework for TypeScript back ends
Hey HN! Suites is a unit-testing framework for TypeScript backend systems working with dependency injection. It introduces a single declarative API for unit testing: wrap any unit with a single call and receive a correct test environment for the unit and its dependencies. // Test a class in complete isolation, all dependencies mocked TestBed.solitary(OrderService).compile(); // Or, test how it integrates with a real dependency TestBed.sociable(OrderService) .expose(PaymentProcessor) // Use the real class .compile(); The backstory: while working for a…
In plain words
Suites is a unit-testing framework for TypeScript backends that use dependency injection. It provides a single declarative API to wrap units and automatically generate correct test environments with their dependencies. Developers can test classes in complete isolation with all dependencies mocked, or test integration with real dependencies selectively. Built for teams writing large numbers of backend tests, it reduces boilerplate code and improves maintainability.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
Hey HN! Suites is a unit-testing framework for TypeScript backend systems working with dependency injection. It introduces a single declarative API for unit testing: wrap any unit with a single call and receive a correct test environment for the unit and its dependencies. // Test a class in complete isolation, all dependencies mocked TestBed.solitary(OrderService).compile(); // Or, test how it integrates with a real dependency TestBed.sociable(OrderService) .expose(PaymentProcessor) // Use the real class .compile(); The backstory: while working for a fast-growing fintech startup 4 years ago, my team had to write thousands of unit tests for our NestJS backend. To scale our efforts, I've built a unit-testing framework which eliminated a significant part of the tests' code and made them a whole lot more maintainable. I open-sourced it, generalized it to support more tech stacks, and soon it gained traction. The problem - unit testing becomes a nightmare very fast: - You mock dependencies by hand, wire them up manually, and spend more time maintaining tests than writing them. - Unit tests are leaky and error-prone since it's unclear which dependencies are mocked - Test intention is lost in the boilerplate - Each engineer invents their own conventions - Tests break during refactors because of untyped, loosely connected mocks - Missing mock implementations go unnoticed, so tests falsely fail on unexpected undefined returns or validate the wrong behavior - Test errors for wrong mocking are confusing to engineers and coding agents alike The nitty-gritty details: - Fluent, auto-discoverable, fully-typed API. - DI Framework Adapters: Works out of the box with NestJS and InversifyJS - Testing Library Adapters: Works out of the box with Jest, Sinon, and Vitest Suites provide two modes of testing: (inspired by Martin Fowler's writings [0]) - Solitary: For testing units in a vacuum, it creates type-safe mocks of all the unit's direct dependencies. - Sociable: For testing units with other related units, it allows the developer to define which dependencies to mock. Eliminating boilerplate and making mocks type-safe drastically helps coding agents (e.g. Claude Code) to write correct tests in a single pass and avoid entering infinite loops, significantly reducing token cost. You can read more about Suites on our website: https://suites.dev What's next? - A dedicated skill for Claude Code - Extended docs with real-world patterns - More test utilities for common backend scenarios Suites is fully open-source and actively maintained for 4 years. I would love you to check it out and get your honest feedback! [0] https://martinfowler.com/bliki/UnitTest.html
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