testutil: add README.md

I've neglected to include a readme for the testutil.  This is the start of
one which hopefully explains why testutil exists distinct from other test
options and how to use it.

Signed-off-by: Tim Pepper <[email protected]>

testutil/README.md

@@ -0,0 +1,55 @@
+Ciao Testutil
+=============
+
+A given ciao component will have unit tests which cover its internals in a
+component specific way.  But this is limited in scope and cannot cover all
+of the component's functionality, because that functionality is ultimately
+about creating and servicing SSNTP command/event/error/status flows.
+
+To enable testing of those SSNTP flows, the testutil package provides
+a set of common test tools for ciao.  Included are:
+
+* shared payload constants
+* shared test certificates
+* test agent implementation for ssntp.AGENT and ssntp.NETAGENT roles
+* test controller implementation for ssntp.Controller role
+* test server implementation for ssntp.SERVER role
+* example client-server test spanning the above SSNTP actors
+* channels for tracking command/event/error/status flows across the SSNTP
+  test actors
+
+This allows a ciao component to be tested more meaninfully, but in partial
+isolation.  The ciao component under test would be a real implementation,
+but its SSNTP peers are the shared synthetic implementations from the
+testutil package.
+
+For an example of how to enable basic SSNTP test flows
+and track the results through the channel helpers
+review the internals of the [example client-server
+test](https://github.com/01org/ciao/blob/master/testutil/client_server_test.go).
+
+Additional test options
+=======================
+
+Virtual
+-------
+
+The next level of test breadth comes from actually running
+a test cluster with real implementations of each ciao
+component.  This is provided in a controlled fashion via the
+[singlevm](https://github.com/01org/ciao/tree/master/testutil/singlevm)
+CI script, which has detailed documentation
+on the wiki at [Single VM Development
+Environment](https://github.com/01org/ciao/wiki/HOWTO:-Single-VM-Development-Environment).
+
+Physical
+--------
+
+Testing is of course also possible on a real hardware cluster which has
+been set up according to the [cluster setup
+guide](https://clearlinux.org/documentation/ciao-cluster-setup.html).
+A minimal Build Acceptance Test (BAT) framework outputting TAP
+(Test Anything Protocol) results is published [in our release
+tools](https://github.com/01org/ciao/tree/master/_release/bat).
+The python script drives ciao-cli to query and manipulate the state of
+a cluster.