Support testing Functions

README.adoc

@@ -110,7 +110,25 @@ Namespace for each babashka source file created side by side with `handler.clj`
 
 See the link:examples[examples] directory to find a fully working set of OpenFaaS Functions written in Babashka.
 
-== Tests
+== Function tests
+
+To test the code of a Function, create a `test` directory in the Function top-level directory, containing:
+
+- `run-tests.clj`: A script that runs the tests. You can use any test library and test runner you like.
+- `bb.edn`: with `{:paths ["../.."]}`
+
+To disable running existing tests, set the `TEST` build time argument to `false`:
+[source, yml]
+----
+my-function:
+  lang: bb
+  handler: ./anything/my-function
+  image: ${DOCKER_REGISTRY_IMG_ORG_PATH}/my-function
+   build_args:
+      TEST: false
+----
+
+== faas-bb tests
 
 === CI tests
 

examples/http/bb-hello/test/bb.edn

@@ -0,0 +1,2 @@
+{:paths ["../.."]
+ :deps {eg/eg {:mvn/version "0.5.6-alpha"}}}

examples/http/bb-hello/test/run-tests.clj

@@ -0,0 +1,11 @@
+(ns function.test.run-tests
+  (:require [eg :refer [eg]]
+            [clojure.test :refer [run-tests]]
+            [function.handler :refer [handler]]))
+
+(eg handler
+  {:body "foo"} => {:body "Hello, foo"})
+
+(let [{:keys [fail error]} (run-tests 'function.test.run-tests)]
+  (when (pos? (+ fail error))
+    (System/exit 1)))

template/bb/Dockerfile

@@ -4,6 +4,8 @@ FROM clojure:tools-deps-1.11.1.1347
 
 RUN set -e
 
+ARG TEST=true
+
 COPY --from=watchdog /fwatchdog /usr/bin/fwatchdog
 COPY --from=babashka /usr/local/bin/bb /usr/local/bin/bb
 
@@ -27,6 +29,13 @@ RUN rm function/bb.edn
 COPY --chown=app:app index.clj ./
 COPY --chown=app:app lib ./
 
+ENV TEST_DIR $HOME/function/test
+
+RUN if [ $TEST != false ] && [ -d $TEST_DIR ]; then \
+      /bin/sh -c "cd $TEST_DIR && bb run-tests.clj" && \
+      rm -rf $TEST_DIR; \
+    fi
+
 ENV mode="http"
 ENV upstream_url="http://127.0.0.1:8082"