Add basic test suite for Blimp

blimp/docs/test.md

+# Testing
+
+Blimp only supports building using [GN](../../tools/gn/README.md), and only
+supports building for Android and Linux.  See [building](build.md) for general
+GN setup.
+
+## Testing on Android
+
+Run the following command to build the Android tests:
+
+```bash
+ninja -C out-android/Debug blimp_tests
+```
+
+### Running the Java instrumentation tests
+
+Install the Blimp APK with the following:
+
+```bash
+./build/android/adb_install_apk.py $(PRODUCT_DIR)/apks/Blimp.apk
+```
+
+Run the Java instrumentation tests (with an optional test filter) with the
+following:
+
+```bash
+$(PRODUCT_DIR)/bin/run_blimp_test_apk [ -f DummyTest#* ]
+```
+
+### Testing on Linux
+
+Run the following command to build the Linux tests:
+
+```bash
+ninja -C out-linux/Debug blimp_tests
+```
+
+There are no tests that run on Linux yet.