Adding overview of tests, based on David's doc.
Change-Id: I3e2e262966a0584a43a86a49570d0d3db7cff09f
diff --git a/docs/Testing.md b/docs/Testing.md
index b4946c9..8a33ee2 100644
--- a/docs/Testing.md
+++ b/docs/Testing.md
@@ -1,7 +1,38 @@
# Testing
-Testing of Hafnium is currently evolving. There are basic tests running on QEMU
-but we want more and more kinds of tests e.g. unit tests.
+## Overview
+
+Hafnium has 4 main kinds of tests:
+
+1. Host tests
+ * Unit tests of core functionality, e.g. page table manipulation.
+ * Source in `src/*_test.cc`.
+ * Using the [Google Test](https://github.com/google/googletest) framework,
+ built against 'fake' architecture (`src/arch/fake`).
+1. Arch tests
+ * Architecture-specific unit tests, e.g. MMU setup.
+ * Source under `test/arch`.
+ * Using our own _hftest_ framework, with `standalone_main.c`.
+ * Build own hypervisor image, run in EL2.
+1. VM API tests
+ * Exercise hypervisor API from both primary and secondary VMs.
+ * Source under `test/vmapi`.
+ * Tests are run from the primary VM under a normal build of the Hafnium
+ hypervisor, possibly communicating with a helper service in one or more
+ secondary VMs.
+ * Using our own _hftest_ framework, with `standalone_main.c` for the
+ primary VM and `hftest_service.c` for secondary VMs.
+ * Build own primary and secondary VMs, run in EL1 under actual Hafnium
+ image.
+1. Linux tests
+ * Exercise the Hafnium Linux kernel module.
+ * Source under `test/linux`.
+ * Tests are run from userspace (PID 1) under Linux in the primary VM under
+ Hafnium, possibly with other secondary VMs.
+ * Using our own _hftest_ framework, with `linux_main.c`.
+
+Host tests run directly on the host machine where they are built, whereas the
+other 3 types can run under an emulator such as QEMU, or on real hardware.
## Presubmit
@@ -23,9 +54,9 @@
These tests boot Hafnium on QEMU and the VMs make calls to Hafnium to test its
behaviour.
-### `hftest`
+### hftest
-Having a framework for tests makes them easier to read and write. `hftest` is a
+Having a framework for tests makes them easier to read and write. _hftest_ is a
framework to meet the needs of VM based tests for Hafnium. It consists of:
* assertions
