docs: add test architecture design doc draft

docs/test-architecture.md

+Testing via Helm
+================
+
+Problem Summary
+---------------
+
+Currently in helm/charts we have a simple way of health-checking charts which
+checks that all pods in the chart reach "Running" state on a running Kubernetes
+cluster. In order to build a system that holds chart quality at the forefront,
+we need to introduce an easy way to create and run potentially more complex
+application-centric tests.
+
+Proposed Solution
+-----------------
+
+#### User Experience
+
+```
+# helm/dm UX for installing charts stays the same
+
+# addition to UX giving easy-to-run tests:
+helm test deis
+
+```
+
+#### Helm's new `test` Command
+
+This command uses test logic located in `<chart name>/tests/` to ensure that
+the chart is operating as intended in an end to end or system test sort of
+fashion.
+
+The command is fairly simple - all it does is load a set of charts into a
+Kubernetes cluster (might be the same or different as the deployed chart).
+What usually makes sense to have is a one-off pod that runs to completion and
+exits with a certain exit code: non-zero signifying failure or zero signifying
+success. The pod is not automatically restarted so that humans or automated
+tools can inspect the results which might be a log, test artifact, or something
+else. `helm test` should therefore be able to be rerun the tests over and over and
+not be hindered by an existing similarly-named set of pods, rcs, or services.
+
+By forcing tests to also be containerized and Kubernetes-ready we have the
+benefit of having a single and easily understandable entry point - it's just
+another set of Kubernetes components.
+
+#### Modifications to Chart Structure
+
+```
+ROOT/
+  Chart.yaml
+  LICENSE
+  README.md
+  ...
+  tests/
+    Chart.yaml
+    templates/
+      some.yaml
+      some.jinja
+      some.jinja.schema
+```