Add 11.md with basic skeleton

Signed-off-by: Csongor Vogel <[email protected]>

.gitignore

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 /.idea
-/local
+/local
+
+# Flutter versions related
+.fvm/

material/11.md

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+# How to use Platform-specific APIs with Platform Channels and testing Flutter Apps
+
+In the previous chapters we've learned how could we use Flutter APIs.
+
+## Platform Channels
+
+## Introduction to test Flutter applications
+TODO
+
+### Unit tests
+
+#### Writing the first unit test
+
+#### Testing model classes
+
+#### Testing Platform Channels
+
+#### Testing BloCs
+
+### Widget tests
+TODO
+
+## Further reading, materials
+
+- [Writing custom platform-specific code](https://flutter.dev/docs/development/platform-integration/platform-channels)
+- [Flutter Platform Channels](https://medium.com/flutter/flutter-platform-channels-ce7f540a104e) by Mikkel Ravn
+- [Intro to Platform Channels: Building an Image Picker in Flutter](https://codewithandrea.com/articles/platform-channels-flutter/) by Andrea Bizzotto
+- [Your Own Image Picker With Flutter Channels](https://www.raywenderlich.com/2882495-your-own-image-picker-with-flutter-channels) by JB Lorenzo
+
+- [Testing Flutter apps](https://flutter.dev/docs/testing)
+- [An introduction to unit testing](https://flutter.dev/docs/cookbook/testing/unit/introduction)
+- [Mock dependencies using Mockito](https://flutter.dev/docs/cookbook/testing/unit/mocking)
+- [An introduction to widget testing](https://flutter.dev/docs/cookbook/testing/widget/introduction)