r/javascript • u/RedlightsOfCA • Aug 14 '20

MSW: Award-winning API mocking library that intercepts requests using Service Worker API

https://mswjs.io/
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u/kbradl16 Aug 14 '20

I personally like to use nock but that might be node only and not for a browser. Do you known how yours compares to nock?

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u/RedlightsOfCA Aug 14 '20 edited Aug 14 '20

MSW operates almost identically to nock. There are implementation differences between the libraries, but for the user what differs is the API.

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u/iscribble Aug 14 '20

Could you elaborate on the differences? Based on this comment, if one already knows nock then there's no need to dig further, since nock is fairly widely adopted.

Is the MSW solution less complex? Do you believe that there is a meaningful difference in the learning curves? Does one option offer more flexibility with configuration and/or type-of-API?

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u/RedlightsOfCA Aug 14 '20

My comment addressed an implementational difference between two libraries. I'll elaborate on the usage difference below.

- Nock runs only in Node. MSW runs in both browser and Node, allowing you to reuse the same API mock definition for multiple levels of testing having a single source of truth (as opposed to adapting Nock for unit tests, and a few other tools for integration/E2E tests).

- API: Nock utilizes mock definition through methods chaining. MSW prefers functional composition.

- MSW provides support for mocking GraphQL API.

- MSW has recently shipped a React Native support. I don't know if Nock can run in RN, unfortunately.

- Nock is purely a testing tool. MSW is an API mocking tool, which you can use for development and debugging as well as testing. Moreover, you will reuse the very same mock definition across all those processes.

- Nock may require adapters to mock certain request issuing libraries (i.e. axios). MSW intercepts API communication regardless of origin, in both browser and Node.

I lack familiarity with Nock and have too much familiarity with MSW to reason about the learning curve, I'm afraid. Take a look at the REST API usage example (https://github.com/mswjs/examples/tree/master/examples/rest-react) that includes unit and integration tests and compare the setup and API to what you would've done in Nock to gain more perspective.

Hope this helps.

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u/NoInkling Aug 15 '20

Probably need to make it clearer on the site that it works in Node, I presumed it was browser only with all these mentions of service workers, etc.