docs: Updated for new test options

Created a new README for the tests and updated the top-level README
with brief details on how to run tests.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>

README.md

@@ -12,6 +12,7 @@
         * [Image with systemd as init](#image-with-systemd-as-init)
         * [Image with the agent as init](#image-with-the-agent-as-init)
     * [Initrd creation](#initrd-creation)
+    * [Tests](#tests)
 * [Platform-Distro Compatibility Matrix](#platform-distro-compatibility-matrix)
 
 ## Introduction
@@ -109,6 +110,14 @@ $ sudo -E PATH=$PATH make AGENT_INIT=yes initrd-only
 For further details,
 see [the initrd builder documentation](initrd-builder/README.md).
 
+### Tests
+
+```
+$ make test
+```
+
+For further details, see [the tests documentation](tests/README.md).
+
 ## Platform-Distro Compatibility Matrix
 
 | | Alpine | CentOS | ClearLinux | EulerOS | Fedora | 

tests/README.md

@@ -0,0 +1,26 @@
+* [Run the osbuilder tests](#run-the-osbuilder-tests)
+* [Further information](#further-information)
+
+## Run the osbuilder tests
+
+osbuilder provides a test script that creates all images and initrds for all
+supported distributions and then tests them to ensure a Kata Container can
+be created with each.
+
+The test script installs all required Kata components on the host system
+before creating the images.
+
+To run all available osbuilder tests:
+
+```
+$ ./test_images.sh
+```
+
+## Further information
+
+The test script provides various options to modify the way it runs. For full
+details:
+
+```
+$ ./test_images.sh -h
+```