feat(std/testing): Add support for object assertion against object subset

[lowlighter]

This add supports for a new assertion function assertObjectMatch which allows to test an actual object against an expected object subset (i.e. inclusivity, not equality)

Why ?

It's often useful to test an object partly without testing the remaining properties (like for web api response, where you might want to only check a few fields).

This function filters out actual object with expected object subsets keys before calling assertEquals (so it's actually a wrapper which acts as a syntaxic sugar).

const a  = {
   foo: true,
   bar: true,
   baz: {
     qux: true
   }
}

// Simple assertions
assertObjectMatch(a, {foo: true})  // OK 
assertObjectMatch(a, {bar: true})  // OK
assertObjectMatch(a, {foo: false}) // KO 

// Nested assertions
assertObjectMatch(a, {baz: {qux: true}}) // OK
assertObjectMatch(a, {baz: {qux:null}})  // KO

[CLAassistant]

All committers have signed the CLA.

[bartlomieju]

Thanks for the contribution @lowlighter! Is there some prior art for this assertion?

@nayeemrmn PTAL

[nayeemrmn]

Should symbols be allowed?

[lowlighter]

Is there some prior art for this assertion?

Yes, it's heavily inspired from expect.toMatchObject(object) from Jest JavaScript testing framework, though implementation may differ a bit. Since a lot of logic has already been done in assertEquals, I thought it would easier to filter the actual object with the expected one so it'll behave the same.

Should symbols be allowed?

Yes, I'll add them and add tests to cover them !

[bartlomieju]

Yes, it's heavily inspired from expect.toMatchObject(object) from Jest JavaScript testing framework, though implementation may differ a bit. Since a lot of logic has already been done in assertEquals, I thought it would easier to filter the actual object with the expected one so it'll behave the same.

@lowlighter thanks, that sounds good to me. I'll wait for @nayeemrmn's review before landing

[nayeemrmn]

I don't think Object.entries() includes symbols. This would be shown if the tests included an erroneous case for symbols. You can use [...Object.getOwnPropertyNames(a), ...Object.getOwnPropertySymbols(a)] to get a complete list of keys.

[lowlighter]

I replaced Object.entries() with your suggestion and it works like a charm, and changed string|symbol by PropertyKey which seems more accurate.

I got some trouble with using symbol as index signature so I casted them into string but not sure it's the cleanest way...

I wanted to add an erroneous case like you suggested, but seems that assertEquals does not handle symbols perfectly currently (unless I missed something) :

import { assertEquals } from "https://deno.land/std/testing/asserts.ts"
const foo = Symbol("foo")
Deno.test("symbol1", () => assertEquals({[foo]:"bar"}, {[foo]:"bar"}))
Deno.test("symbol2", () => assertEquals({[foo]:"bar"}, {[Symbol("foo")]:"bar"}))

running 2 tests
test symbol1 ... ok (2ms)
test symbol2 ... ok (1ms)

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out (4ms)

[nayeemrmn]

LGTM

[bartlomieju]

LGTM, thanks @lowlighter