[CI] Add coverage

.github/workflows/dart.yml

@@ -7,9 +7,9 @@ name: Dart
 
 on:
   push:
-    branches: [ "master" ]
+    branches: ['master']
   pull_request:
-    branches: [ "master" ]
+    branches: ['master']
 
 jobs:
   build:
@@ -40,3 +40,30 @@ jobs:
       # want to change this to 'flutter test'.
       - name: Run tests
         run: dart test
+
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      # Note: This workflow uses the latest stable version of the Dart SDK.
+      # You can specify other versions if desired, see documentation here:
+      # https://github.com/dart-lang/setup-dart/blob/main/README.md
+      # - uses: dart-lang/setup-dart@v1
+      - uses: dart-lang/setup-dart@9a04e6d73cca37bd455e0608d7e5092f881fd603
+
+      - name: Install dependencies
+        run: dart pub get
+
+      - name: Install coverage tools
+        run: dart pub global activate coverage
+
+      - name: Run coverage
+        run: dart pub global run coverage:test_with_coverage
+
+      - name: Upload coverage
+        uses: codecov/codecov-action@v4
+        with:
+          fail_ci_if_error: true # optional (default = false)
+          token: ${{ secrets.CODECOV_TOKEN }} # required
+          verbose: true # optional (default = false)

README.md

@@ -2,6 +2,7 @@
 
 [![Dart](https://github.com/MatthiWare/mediator.dart/actions/workflows/dart.yml/badge.svg?branch=master)](https://github.com/MatthiWare/mediator.dart/actions/workflows/dart.yml)
 [![pub package](https://img.shields.io/pub/v/dart_mediator.svg?label=dart_mediator&color=blue)](https://pub.dartlang.org/packages/dart_mediator)
+[![codecov](https://codecov.io/gh/MatthiWare/mediator.dart/graph/badge.svg?token=W1WQDQEZIJ)](https://codecov.io/gh/MatthiWare/mediator.dart)
 
 # Description