Add build arg to control the test command

**What**
- Add a build arg TEST_COMMAND that allows the
  developer to set the exact test command that
  should be executed. When set to `off` the tests
  will be skipped

Signed-off-by: Lucas Roesler <roesler.lucas@gmail.com>

Author: LucasRoesler

template/python3-flask/Dockerfile

@@ -39,7 +39,13 @@ USER root
 
 COPY function/   .
 RUN chown -R app:app ../
-RUN  tox -l == 0 && tox
+
+ARG TEST_COMMAND=tox
+RUN if [ "x$TEST_COMMAND" = "xoff" ]; then \
+    echo "skipping tests";\
+    else \
+    eval "$TEST_COMMAND"; \
+    fi
 
 WORKDIR /home/app/
 

template/python3-flask/function/handler_test.py

@@ -1,8 +1,9 @@
 from .handler import handle
 
 # Test your handler here
-# To disable testing, you need to update the
-# tox.ini file, in addition to deleting this file.
+
+# To disable testing, you can set the build_arg `TEST_COMMAND=off` on the CLI or in your stack.yml
+# https://docs.openfaas.com/reference/yaml/#function-build-args-build-args
 
 def test_handle():
     # assert handle("input") == "input"