Repository: flutter
Issue: Testing Code Coverage percentage does not include untested (not imported) files
Labels: a: tests,tool,has reproducible steps,P2,customer: castaway,team-tool,triaged-tool,found in release: 3.19,found in release: 3.21

### Steps to reproduce

[flutter_demo.zip](https://github.com/flutter/flutter/files/14725661/flutter_demo.zip)
1. Open example flutter project
2. Run `flutter test --coverage` and observe coverage is measured at 83.3%.
3. Uncomment the import for `otherutils.dart` inside of `stringutils_test.dart`.
4. Run `flutter test --coverage` again and observe code coverage is measured at 41.7%.

### Expected results

Code coverage should take into account of all source files and not just the ones that are tested or imported.

### Actual results

Code coverage only takes into account of source files that are tested or imported.

### Code sample

<details open><summary>Code sample</summary>

```dart
[Paste your code here]
```

</details>


### Screenshots or Video

<details open>
<summary>Screenshots / Video demonstration</summary>

[Upload media here]

</details>


### Logs

<details open><summary>Logs</summary>

```console
[Paste your logs here]
```

</details>


### Flutter Doctor output

[✓] Flutter (Channel stable, 3.19.2, on macOS 14.2.1 23C71 darwin-x64, locale
    en-US)
    • Flutter version 3.19.2 on channel stable at
      /Users/kevin.nguyen/development/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 7482962148 (3 weeks ago), 2024-02-27 16:51:22 -0500
    • Engine revision 04817c99c9
    • Dart version 3.3.0
    • DevTools version 2.31.1

[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
    • Android SDK at /Users/kevin.nguyen/Library/Android/sdk
    • Platform android-34, build-tools 34.0.0
    • Java binary at: /Applications/Android
      Studio.app/Contents/jbr/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build
      17.0.7+0-17.0.7b1000.6-10550314)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 15.2)
    • Xcode at /Applications/Xcode-15.2.0.app/Contents/Developer
    • Build 15C500b
    • CocoaPods version 1.14.3

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2023.1)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build
      17.0.7+0-17.0.7b1000.6-10550314)

[✓] VS Code (version 1.87.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.84.0

[✓] Connected device (2 available)
    • macOS (desktop) • macos  • darwin-x64     • macOS 14.2.1 23C71 darwin-x64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 122.0.6261.129

[✓] Network resources
    • All expected network resources are available.

• No issues found!