dart-migrate-to-checks-package

Contents

• Why Migrate to package:checks
• Dependency Management
• Assertion Mapping and Syntax Guidelines
• Advanced Asynchronous Assertions
• Workflow: Executing Syntax Migrations
• Examples

Why Migrate to package:checks

package:checks is a modern assertion library maintained by the Dart team that replaces package:matcher. It offers several benefits over traditional matchers:

• Fluent API: Chain assertions naturally using Dart methods instead of nested helper functions.
• Type Safety: Benefit from compiler checks on expected properties, preventing type mismatches in tests.
• Descriptive Diagnostics: Read extremely clear failure messages showing exactly what failed and why (e.g. displaying collection differences).

Dependency Management

To add the checks library to your package: