Migrate type tests to TSTyche

[mrazauskas]

Thanks for using jest-runner-tsd and tsd-lite to test types. I am was maintaining tsd-lite and helping with the runner too.

Just wanted to let you know that tsd-lite got deprecated. It is replaced with TSTyche, a mighty type testing tool that I was developing for two years.

The problem is that architecture of tsd is very limiting. Without maintaining forked tsd-lite it was not possible to upgrade TypeScript in Jest repo. tsd-lite was temporary solution to get unblocked and to learn more about type testing.

I was contributing type tests to Jest repo for some time. There are around 1200 assertions. At this scale it was a pain debugging types. So I went on researching and building TSTyche. Similar to tsd, it compares types programmatically, but the rest is different.

I just try to explain that TSTyche is build to work at any scale and to last for year. That's why I would like to recommend to use it in your project.

Currently TSTyche is used by Immutable.js, Jest, Redwood and few more smaller project (including my own packages).

Repo: https://github.com/tstyche/tstyche
Documentation: https://tstyche.org

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TSTyche has test() and describe() helpers which support run mode flags like .only, .skip or .todo. These are priceless if you have to debug something. By the way, additionally there are expect.fail expect.only or expect.skip.

--only and --skip can be set from the command line: tstyche useful-types --only DeepPartial.

It has expect style assertions which look familiar. An expression or a type can be passed on both sides of an assertion. This means that TSTyche is able to compare two types directly. There is no need to create intermediate values.

Testing on several versions of TypeScript is supported: tstyche --target 4.9,current. This command would use TypeScript 4.9 and the one from node_modules (the current).

By default TSTyche uses typescript from node_modules. There is no need to install patched TypeScript package like @tsd/typescript. The install size of TSTyche is under 200kB. It has no dependencies.

TSTyche is fast. Just give it a spin.

And there is much more.

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Curious what you think.

[mrazauskas]

.toMatch() is used to check partial matching, otherwise .toEqual() is used. .toEqual() would not work here because the type is recursive.

[mrazauskas]

.toMatch() checks readonly modifiers strictly.

[mrazauskas]

Hard to say what was the problem and why "need to fix this" note is left here. As far as I can get, it all works as expected.

[mrazauskas]

The diff is noisy, but it was so tempting to use describe() and it().

[mrazauskas]

Hm.. Not sure what to do with Node.js 14. TSTyche is using AbortSignal.timeout() which is available from Node.js 16.14. If Node.js 14 support is a hard requirement, I can try reimplement AbortSignal.timeout(). The rest should work.

Apparently AbortController is experimental feature in Node.js 14. That’s more work, but still possible to reimplement. It is used only internally to handle --failFast. To be honest, I was thinking to add light reimplementation, because AbortSignal.any() would be useful too (add in Node.js 20.3 only). Also currently TypeScript supports Node.js ^14.17.0, so it makes sense to have similar capabilities.

[mrazauskas]

Files are renamed because of two reasons: TSTyche suggest using .tst.ts suffix, because it is shorted and reflex the aim better (not executable test file); no need to have tstyche.config.json, less files in the root.

[mrazauskas]

There are only unrelated failures in e2e. The rest works as expected.

This PR is ready for review. Or at least some feed back (;