I've been coding in React-Native for a while and when I need to I write some native Android code as well. However, I had not seen this gradle task until I started using a library which used this particular gradle task.
That library is an end-to-end testing library (detox), and it uses this command "cd android && ./gradlew assembleDebug assembleAndroidTest -DtestBuildType=debug && cd .." to build the android .apk that will be used in the automated e2e test. Actually it builds two apks, the debug one and the AndroidTest one, but I don't know where the latter comes from or where it's configured or where the docs are about this.
I searched for an hour and did not find anything other than this very short description:
assembleAndroidTest - Assembles all the Test applications.
What are the Test applications?
Also, what is -DtestBuildType=debug?