Lesson 22: Using golden files to verify pixel-perfect widgets

[samuelematias]

Description

PR with Lesson 22.

matchesGoldenFile

For the first time, when you run a test (flutter test) with some GoldenFile tests (matchesGoldenFile), you will get an error.

Because the GoldenFile(s) still doesn't exist, so to fix this error, you need to run the test with this command
flutter test --update-goldens, and your test will pass.

Now, if you check your project, you will see a new folder inside your test folder, with the name goldens.

And with some screenshots like this:

Now, if you change something in your code that changes the pixel of the widget, something like changing the AppBar title from Calculator to Calculat:

Your golden test will fail because of the pixel of the AppBar title change! So, no more pixel-perfect.

Now, if you check your project, you will see a new folder inside your test folder, with the name failures.

And with some screenshots indicating where the pixel change, like this:

Types of changes

• Fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (non-breaking change which adds Improvements)