chore: various tweaks to support running tests in the CI

Makefile

@@ -96,3 +96,21 @@ ifneq ($(DOCKER_TAG_VERSION),)
 		"$(DOCKER_IMAGE):$(DOCKER_TAG_VERSION)" && \
 		docker push "$(DOCKER_IMAGE):$(DOCKER_TAG_VERSION)"
 endif
+
+# ==============================================================================
+# Tests
+# ==============================================================================
+
+.PHONY: ci-test
+ci-test: docker-ci-build
+	$(eval IMAGE := $(shell $(DOCKER_CI_BUILD_CMD) -q))
+	$(eval RAND := $(shell echo "$${RANDOM}$$(date +%s)"))
+	POSTAL_IMAGE=$(IMAGE) \
+	docker-compose -p "postal$(RAND)" run --rm postal sh -c 'bundle exec rspec'; \
+	EXIT_CODE=$$?; \
+	docker-compose -p "postal$(RAND)" down -v; \
+	exit $$EXIT_CODE
+
+.PHONY: test
+test:
+	bundle exec rspec