mjackson/expect

Document that the jest code mods won't cover all cases?

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#230 opened on Sep 9, 2017

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documentationhelp wanted

Description

I'm trying out migrating from mocha & expect to just jest.

The code mods handled most of the cases, but there are some MAJOR differences in how Jest's isEqual matcher works, mostly because it does not use the is-equal package anymore.

This means things like this worked with expect but DO NOT work with jest:

expect(["abc"]).toEqual("abc");

function createEnhancedFunction() {
  var myFunction = function() { return "a value"; };
  myFunction.a = "123";
  return myFunction;
}

expect({ a: createEnhancedFunction() }).toEqual({ a: createEnhancedFunction() });

The first difference is easy to work around, but the second one (inability to compare functions and treat them as equal) has me a little stumped.

I'd think it would be good to emphasize that is-equal is no longer used for equality checks, and maybe suggest some workarounds in the docs?

Contributor guide

Tech stack
javascript
Domain
testing
Issue type
documentation
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
None
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80
Research direction
Investigate the current documentation of the expect library to see if it already mentions the differences between expect and jest equality matchers. If not, add a section highlighting that jest no longer uses the `is equal` package and provide workarounds for common cases like comparing functions or arrays. Consider linking to relevant files such as README.md or the docs folder.