HACKING.md: added with testing instructions

Add instructions how to run the unit tests as well as the full
local test environment.

HACKING.md

@@ -0,0 +1,108 @@
+# Testing
+
+## Unit tests
+
+To support local development an container `test/Dockerfile` contains
+the environment to test all three plugins. It can be built and run
+via `./run-test.sh`. This will execute the unit tests as well as
+run pylint and ShellCheck on the source code.
+
+## Local integration testing
+
+### Preparation
+
+This assumes that osbuild-composer, version greater than 21, is
+installed on the host and the koji API is enabled.
+
+Make certificates for osbuild-composer. This is needed to authorize
+clients to use the composer API. There is a script that will create
+the certificates and also copy it to the correct places in `/etc`.
+
+```
+sudo test/make-certs.sh
+```
+
+Build the containers:
+```
+sudo test/build-container.sh
+```
+
+### Setup the infrastructure containers
+
+Run the infra containers, i.e. the database server, the kerberos kdc,
+and koji hub. This will also create the kerberos keytabs needed for
+the koji builder to authorize itself to koji hub.
+
+```
+sudo ./run-koji-container.sh start
+```
+
+Koji web will now be running at: http://localhost/koji/
+
+
+Copy the credentials: The TLS certificates for the koji builder plugin
+to make authorize requests to composer and the kerberos keytabs
+needed for composer and worker (of composer) to reserve and import the
+build via the koji XML RPC.
+
+```
+sudo  test/copy-creds.sh
+```
+
+### Run the koji builder
+
+Run the koji builder instance can be started. Here `fg` means that
+it will be running in the foreground, so logs can be inspected and
+the container stopped via `ctrl+c`.
+
+```
+sudo ./run-builder.sh fg
+```
+
+### Setup the tags
+
+In order to build an image, a series of tags needs to be created.
+Specifically:
+
+ * the target tag
+ * the build tag, which contains the architectures
+ * destination tag, which contains the list of packages
+
+A helper script will create a minimum set that is necessary to build
+an image call `Fedora-Cloud` for `f32-candidate`:
+
+```
+./make-tags.sh
+```
+
+### Client plugin
+
+The client plugin needs to be installed either by creating the RPMs
+first via meson, or via a symlink from the checkout to the koji cli
+plugin directory:
+
+```
+mkdir -p /usr/lib/python3.8/site-packages/koji/koji_cli_plugins/
+ln -s plugins/cli/osbuild.py \
+	  /usr/lib/python3.8/site-packages/koji/koji_cli_plugins/osbuild.py
+```
+
+### Making a build
+
+Now that all is setup a build can be created via:
+
+```
+koji --server=http://localhost/kojihub \
+     --user=kojiadmin \
+	 --password=kojipass \
+	 --authtype=password \
+	 osbuild-image \
+	 Fedora-Cloud \
+	 32 \
+	 fedora-32 \
+	 f32-candidate \
+	 x86_64 \
+	 --repo 'http://download.fedoraproject.org/pub/fedora/linux/releases/32/Everything/$arch/os/' \
+	 --image-type qcow2 \
+	 --release 1
+```