Write tests for immutableMap

immutableMap is an internal module. It’s an abstract module. I wonder if anyone would be interested in writing tests for it. Note that we want to test the api, not the implementation (the type ImmutableMap is representing implementation), because the goal is to come up with better implementation with same functionality.

[dominictwlee]

@dominictwlee Glad you start investigating it. So, the background of this work is to improve performance. If we have many atoms, our immutableMap becomes big which can cause bad performance of the entire library.

Originally, the code is embedded in Provider.ts, but as we move it to immutableMap.ts, we can compare different implementations. To compare different implementations, we need to test it (this issue) and measure peformance (#108).

As an example, the original implementation of immutable map is just a map which is copied on set.

const mCreate = () => new Map()
const mGet = (m, k) => m.get(k)
const mSet = (m, k, v) => new Map(m).set(k, v)
...

I still wonder if this is fairly performant.

So, the test would be something like this.

m1 = mCreate()
m2 = mSet(m1, 1, 'a')
mGet(m2, 1) === 'a'
mGet(m1, 1) === undefined // or == null? or !== 'a'
m1 !== m2
m3 = mSet(m2, 1, 'b')
mGet(m2, 1) === 'a'
...

Does it clarify the idea?

Yep makes sense, looks similar to some of the test cases I drafted out. Cool I know where to take it from here, thanks!

[dominictwlee]

Cool, I’ll have a look at it.