Add simple test harness

.gitignore

@@ -0,0 +1 @@
+credentials.test.json

Makefile

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+.PHONY: test
+test:
+	./test/test.sh

README.md

@@ -17,3 +17,12 @@ To run the example module tests after creating a new repository:
 - Create a Service Account key in `/credentials.json` (relative to the new repository location)
 - `cp test/fixtures/shared/terraform.tfvars.sample test/fixtures/shared/terraform.tfvars` and edit `test/fixtures/shared/terraform.tfvars`
 - Run `make test_integration_docker`.
+
+## Automated Testing
+
+When making changes to this template, the tests on the example module should be run to sanity-check changes, with the goal of ensuring that this template is functional at all times. These steps have been automated, and can be run as follows:
+
+1. Download a service account key for the project in which you want to run the generated module's tests as `/credentials.test.json`
+2. Run `make test`
+
+If the automated test fails, it will clean up resources that the module created, and leave `../terraform-google-module-test` in place for review. Otherwise, all resources will be cleaned up, and the generated module will be deleted.

test/test.sh

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+#!/bin/bash
+
+##############################################################
+# Simple Test Harness                                        #
+# Instantiates the cookiecutter template, and runs its tests #
+##############################################################
+
+_curdir=$(pwd)
+cd ..
+cookiecutter --no-input "${_curdir}" module_name=module-test
+cd ./terraform-google-module-test || exit 1
+cp "${_curdir}/credentials.test.json" ./credentials.json
+_project_id=$(cat credentials.json | jq -r '.project_id')
+tee ./test/fixtures/shared/terraform.tfvars <<EOF
+project_id="${_project_id}"
+EOF
+make test_integration_docker
+_result=$?
+if [ "$_result" -ne "0" ]; then
+	make docker_destroy
+	exit $_result
+fi
+cd .. || exit 1
+rm -rf terraform-google-module-test
+cd "${_curdir}" || exit 1