Screenshot tests that show what changed.

One engine for all test runners

The CLI works with each test runner that writes PNG files. The SDKs work inside your test framework. All of them use the same Rust engine and the same .gleon/gleon.yaml file.

• gleon CLI Available

  For each test runner that writes PNG files

  • A summary for each run, with one line for each failure
  • An HTML report that shows the golden, the candidate and the diff
  • Markdown, JUnit and JSON reports for your CI
  • A comment on the pull request. Write /gleon approve to commit the new goldens.
  • Goldens in Git, or manifests in Git and images in S3, R2 or Google Cloud Storage

  gleon init --generic # once
  gleon stage          # record
  gleon diff           # compare
  gleon report html

  Download for macOS, Linux and Windows

• Flutter package Available

  Replaces matchesGoldenFile

  • 5 to 20 times faster than the built-in comparator
  • exact, pixel and ssim tolerance, and ignore regions
  • The real fonts of your app. gleon compares text on the platform that recorded the golden.
  • Works with alchemist, golden_toolkit and golden_screenshot
  • No Rust toolchain is necessary

  import 'package:flutter_test/flutter_test.dart';
  import 'package:gleon/gleon.dart';

  Read the package guide

• More SDKs Coming soon

  For more test frameworks

  • SDKs for more test frameworks are in development
  • They use the same engine, configuration and reports
  • Until then, use the CLI. It compares the PNG files of each test runner.

  # .gleon/gleon.yaml
  screenshots:
    - include: "e2e/**/*.png"
      mode: pixel
      diff:
        threshold: 0.01

  Watch the CLI repository

What changes when you use gleon

Most golden test suites have the same problems. This is what gleon does for each problem.

How it works

Use three commands on your computer and one step in CI. Your test command does not change.

1. Make a workspace

   gleon init makes the .gleon/gleon.yaml file. This file sets the comparison rules for your goldens. Without a tolerance, gleon compares exactly.

   # .gleon/gleon.yaml
   baselines: goldens
   fallback_platform: macos-aarch64
   screenshots:
     - include: "**/test/**/*.png"
       mode: ssim # or exact, pixel
   exclude:
     - "**/failures/**"

2. Run your tests with gleon

   gleon records one run. It shows the totals and one line for each failure. It exits with the exit code of your tests.

   $ gleon test -- flutter test
   Run run-20261020T101500Z-1a2b3c4d: 128 case(s): 125 passed, 3 failed (2 mismatch, 1 missing)
     test/goldens/counter_3: Mismatch: 0.0167% (1 of 6000px) differ (.gleon/runs/latest/cases/macos-aarch64/test/goldens/counter_3.json)

3. Examine and approve

   The HTML report shows each failure with its golden, candidate and diff. gleon approve writes the accepted candidates over their goldens.

   $ gleon report html --out .gleon/runs/latest/report.html
   $ gleon approve

- uses: gleon-rs/gleon@main
  with:
    command: verify
    test-command: flutter test

Speed and proof

The built-in comparator encodes a PNG file for each frame. gleon compares the raw pixels in Rust. It encodes a PNG file only to keep a failure.

Where it runs

You can record goldens on each of these platforms. Each golden records the platform that made it.

Not supported: macOS on Intel, Linux with musl (for example Alpine), web builds and tests on a device. gleon compares PNG images.

Pricing

gleon is free for all users until December 31, 2026. Commercial licenses and their prices come in 2027.

Install

gh release download --repo gleon-rs/gleon --pattern gleon-macos-aarch64
install -m 755 gleon-macos-aarch64 ~/.local/bin/gleon

dev_dependencies:
  gleon:
    git:
      url: https://github.com/gleon-rs/flutter.git
      ref: vX.Y.Z # a release tag

import 'package:flutter_test/flutter_test.dart';
import 'package:gleon/gleon.dart';