avajs/ava

Diffs for arrays of strings can be pretty confusing

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#1,521 opened on Sep 16, 2017

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 (3 comments) (1 reaction) (0 assignees)JavaScript (20,600 stars) (1,408 forks)batch import
bughelp wantedscope:assertionsscope:reporters

Description

If you do t.deepEqual (and I think also t.is) on two arrays containing strings. If there are a large amount of strings and they only differ slightly the output is very confusing. It appears that as soon as a new entry in an array has shifted the items after it across, AVA text diffs every single entry against the same index in the original array.

e.g: An array with 219 strings that has had 6 additions and 1 deletion: AVA diff: https://travis-ci.org/lukechilds/window/jobs/266859856 GitHub diff: https://github.com/lukechilds/window/pull/7/commits/6ecbade39561cf705ddc2833cbc3b93e2abfb223

Contributor guide

Tech stack
javascript
Domain
testing
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
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
JavaScriptBasic understanding of AVAFamiliarity with array diff algorithms
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Review the current diff output logic for arrays in AVA's assertion code, likely in files like lib/assert.js or lib/format diff.js. Analyze the provided examples to understand the alignment issue. Consider implementing a smarter diff that accounts for insertions/deletions rather than index based comparison.