-`yarn run docker-build-android`: Builds a test image with the latest dependencies and React Native library code, including a compiled Android test app.
There are two Dockerfiles for use with the Android codebase.
The base image used to build `reactnativecommunity/react-native-android` is located in the https://github.com/react-native-community/docker-android GitHub repository.
It contains all the necessary prerequisites required to run the React Android tests.
It is separated out into a separate Dockerfile because these are dependencies that rarely change and also because it is quite a beastly image since it contains all the Android dependencies for running Android and the emulators (~9GB).
Once you have downloaded the base image, the test image can be built using `docker build -t reactnativeci/android -f ./.circleci/Dockerfiles/Dockerfile.android .`. This is what `yarn run docker-build-android` does. Note that the `-t` flag is how you tell Docker what to name this image locally. You can then use `docker run -t reactnativeci/android` to run this image.
> Note: `--cap-add=SYS_ADMIN` flag is required for the `.circleci/Dockerfiles/scripts/run-android-docker-unit-tests.sh` and `.circleci/Dockerfiles/scripts/run-android-docker-instrumentation-tests.sh` in order to allow the remounting of `/dev/shm` as writeable so the `buck` build system may write temporary output to that location.
Every time you make any modifications to the codebase, including changes to the test scripts inside `.circleci/Dockerfiles/scripts`, you should re-run the `docker build ...` command in order for your updates to be included in your local docker test image.