Add quick README about testing

test/README.md

@@ -0,0 +1,29 @@
+# osbuild-composer testing information
+
+
+## Integration testing
+
+This will consume the osbuild-composer API surface via the `composer-cli`
+command line interface. Implementation is under `cmd/osbuild-tests/`.
+
+The easiest way to get started with integration testing from a git
+checkout is:
+
+* `make rpm` to build the software under test
+* `dnf install output/x86_64/golang-github-osbuild-composer-*.rpm` - this will
+  install both osbuild-composer, its -debuginfo, -debugsource and -tests packages
+* `systemctl start osbuild-composer`
+* `/usr/libexec/tests/osbuild-composer/osbuild-tests` to execute the test suite.
+  It is best that you use a fresh system for installing and running the tests!
+
+**NOTE:**
+
+The easiest way to start osbuild-composer is via systemd because it takes care
+of setting up the UNIX socket for the API server.
+
+If you are working on a pull request that adds more integration tests
+(without modifying osbuild-composer itself) then you can execute the test suite
+from the local directory without installing it:
+
+* `make build` - will build everything under `cmd/`
+* `./osbuild-tests` - will execute the freshly built integration test suite