JSONAssert VS ts-pattern

And finally, we check that the supplied json equals to the one we got on step 3 (I use JSONAssert library here). The false boolean parameter tells to check only overlapping fields. For example, if the actual result contains the addressV2 field and the expected object doesn’t, it won’t trigger the failure. That’s a normal situation because backward compatibility data is static while the OrderCreated might grow with new parameters.

This can be improved, it'd be worth Googling for a better solution than what you have.

https://github.com/skyscreamer/JSONassert seems decent.

but it can be done from scratch in a few hours (I'd recommend this if you have 'standardized' fields which you may want to ignore):

1) Move to a matcher library for assertions (Hamcrest is decent), and abstract `toJSON` into the a matcher, rather on the input.

This would change the assertion from:

`assertEquals(toJson(someObject), giantJsonBlobFromADifferentFile)`

to:

`assertThat(someObject, jsonEqual(giantJsonBlobFromADifferentFile))`

The difference here is subtle: it allows `jsonEqual` to control the formatting of the test failure output, so on a failure you can:

* convert both of the strings back to JSON

* perform a diff, and provide the diff in the test output.

Decent blog post on the topic: https://veskoiliev.com/use-custom-hamcrest-matchers-to-level...

ts-pattern has been a decent band-aid for the lack of native pattern matching, but obviously has downsides that could be avoided if it was built into the language.

https://github.com/gvergnaud/ts-pattern

ts-pattern

With how powerful the type system is you can implement pattern matching via a library pretty convincingly, https://github.com/gvergnaud/ts-pattern is definitely the go-to. That being said pattern matching is hardly a requirement for being ok for implementing compilers.

https://github.com/gvergnaud/ts-pattern might help

There's a proposal to add something like that to JavaScript but it's been stuck in limbo since 2017 although there are libraries like ts-pattern which implement it already.