README.md: Add instructions on how to run unit tests

Author: nalenz-objectbox

README.md

@@ -39,7 +39,7 @@ To try out the demo code in this repository, follow these steps:
 1. Install [objectbox-c](https://github.com/objectbox/objectbox-c) system-wide: `curl -s https://raw.githubusercontent.com/objectbox/objectbox-c/master/download.sh > /tmp/download.sh && bash /tmp/download.sh 0.7 && rm /tmp/download.sh` (answer Y when it asks about installing to /usr/lib).
 2. Back in this repository, run `pub get` in each of the following directories: `objectbox`, `objectbox_model_generator`, `objectbox_test`. If you just want to try out the tests, running it in `objectbox_test` is enough.
 3. Move into the `objectbox_test` directory and execute `pub run build_runner build`. This regenerates the ObjectBox model to make it usable in Dart (i.e. the file `test/test.g.dart`) and is necessary each time you add or change a class annotated with `@Entity(...)`.
-4. Finally run `dart test/test.dart` to start the demo script.
+4. Finally run `pub run test test/test.dart` to run the unit tests.
 
 Dart integration
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