testing-library/jest-dom

toHaveStyle for property `font-size` behaves incorrectly for number values

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#564 opened on Dec 27, 2023

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buggood first issue

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Description

  • @testing-library/jest-dom version: 6.1.5
  • node version: 20.3.1
  • jest (or vitest) version: 0.34.1
  • npm (or yarn) version: 9.6.7

Relevant code or config:

render(<div data-testid="element" style={{ fontSize: 8 }} />)
expect(screen.getByTestId('element')).toHaveStyle({ fontSize: 1 })

What you did:

I expected the above assertion to fail

What happened:

The test passes instead!✅

Reproduction:

Problem description:

the assertion is clearly incorrect and can easily cause bugs

Suggested solution:

I have not thought of a solution yet but would like to investigate this issue during my off hours.

Contributor guide

Research direction
Inspect the toHaveStyle matcher implementation in jest dom, specifically how it handles numeric values for CSS properties like font size. Look for parsing logic and comparison.
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.
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JavaScriptjest
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75