README: add informatinon on tests and CI/CD

README.md

@@ -9,3 +9,55 @@ cargo run --package graph-builder -- --address 0.0.0.0 --registry https://quay.i
 cargo run --package policy-engine -- --address 0.0.0.0 &
 curl --verbose --header 'Accept:application/json' http://localhost:8081/v1/graph
 ```
+
+## Tests
+There are several ways of testing various parts of the Cincinnati stack.
+
+### Offline
+
+#### Language-Level
+The language-level tests can be run using `cargo --test` in the repository's root directory:
+
+```console
+cargo test
+```
+
+### Online
+The online tests for the graph-builder depend on a curated set of repositories to be available on *quay.io* in the *redhat* organization.
+The build instructions for (re-)populating the repositories are available at *graph-builder/tests/images/build-n-push.sh*.
+The script must run be run from its directory to function:
+
+```console
+cd graph-builder/tests/images
+./build-n-push.sh test-*
+```
+
+#### Language-Level
+The graph-builder package currently has network dependent tests which gated behind the feature `test-net` and `test-net-private`.
+The latter requires setting the environment variable `CINCINNATI_TEST_CREDENTIALS_PATH` which is equivalent to *graph-builder's* `--credentials-path`.
+
+Assuming you have access to images under the *quay.io/redhat* organization, and have an appropriate *$HOME/.docker/config.json* in place, this might work on your machine:
+
+```console
+cd graph-builder
+export CINCINNATI_TEST_CREDENTIALS_PATH="$HOME/.docker/config.json"
+cargo test --features test-net,test-net-private
+```
+
+### CI/CD
+The *dist/* directory contains various CI/CD related files.
+
+#### Openshift Dev
+* Uses *dist/openshift-release/Dockerfile.builder* as the build container
+* Runs `dist/pr_check.sh` for PRs
+* Runs `dist/pr_check.sh` for successful merges to the *master* branch
+
+For details please see [github.com/openshift/release/(...)/openshift-cincinnati-master.yaml][1].
+
+#### App-SRE
+* Uses *dist/build/Dockerfile* as a build container
+* Runs `dist/pr_check.sh` for PRs
+* Runs `dist/build_deploy.sh` for successful merges to the *master* branch and pushes the result to the staging environment *(URL is not yet publicly available)*
+
+[1]: https://github.com/openshift/release/blob/master/ci-operator/config/openshift/cincinnati/openshift-cincinnati-master.yaml
+