Fix tests silently skipped by Docker BuildKit

Docker BuildKit (default since Docker 23.0) optimizes builds by
skipping stages that are not referenced by the final target. The test
stage (FROM build AS test) was not a dependency of the ship stage, so
BuildKit skipped it entirely, meaning tests never ran during
faas-cli build.

Remove the separate test stage and move the test commands into the
build stage which the ship stage depends on, ensuring tests are
always executed when enabled.

Change TEST_ENABLED default from true to false so tests are opt-in
via --build-arg TEST_ENABLED=true.

Signed-off-by: Han Verstraete <han@openfaas.com>

Author: welteki

README.md

@@ -385,17 +385,27 @@ def handle(req):
 
 
 ## Testing
-The `python3` templates will run `pytest` using `tox` during the `faas-cli build`. There are several options for controlling this.
+The `python3` templates support running `pytest` using `tox` during `faas-cli build`. Testing is disabled by default and must be explicitly enabled.
 
-### Disabling testing
-The template exposes the build arg `TEST_ENABLED`. You can completely disable testing during build by passing the following flag to the CLI
+### Enabling testing
+The template exposes the build arg `TEST_ENABLED`. You can enable testing during build by passing the following flag to the CLI
 
 ```sh
---build-arg 'TEST_ENABLED=false'
+--build-arg 'TEST_ENABLED=true'
 ```
 
 You can also set it permanently in your stack.yaml, see the [YAML reference in the docs](https://docs.openfaas.com/reference/yaml/#function-build-args-build-args).
 
+```yaml
+functions:
+  fn:
+    lang: python3-http
+    handler: ./fn
+    image: fn:latest
+    build_args:
+      TEST_ENABLED: "true"
+```
+
 ### Changing the test configuration
 The template creates a default `tox.ini` file, modifying this file can completely control what happens during the test. You can change the test command, for example switching to `nose`. See the [tox docs](https://tox.readthedocs.io/en/latest/index.html) for more details and examples.
 

template/python3-flask-debian/Dockerfile

@@ -47,12 +47,10 @@ USER root
 
 COPY --chown=app:app function/   .
 
-FROM build AS test
 ARG TEST_COMMAND=tox
-ARG TEST_ENABLED=true
+ARG TEST_ENABLED=false
 RUN [ "$TEST_ENABLED" = "false" ] && echo "skipping tests" || eval "$TEST_COMMAND"
 
-
 FROM build AS ship
 WORKDIR /home/app/
 

template/python3-flask-debian/function/handler_test.py

@@ -2,7 +2,7 @@
 
 # Test your handler here
 
-# To disable testing, you can set the build_arg `TEST_ENABLED=false` on the CLI or in your stack.yml
+# To enable testing, you can set the build_arg `TEST_ENABLED=true` on the CLI or in your stack.yml
 # https://docs.openfaas.com/reference/yaml/#function-build-args-build-args
 
 def test_handle():

template/python3-flask/Dockerfile

@@ -45,9 +45,8 @@ USER root
 COPY --chown=app:app function/   .
 
 
-FROM build AS test
 ARG TEST_COMMAND=tox
-ARG TEST_ENABLED=true
+ARG TEST_ENABLED=false
 RUN [ "$TEST_ENABLED" = "false" ] && echo "skipping tests" || eval "$TEST_COMMAND"
 
 FROM build AS ship

template/python3-flask/function/handler_test.py

@@ -2,7 +2,7 @@
 
 # Test your handler here
 
-# To disable testing, you can set the build_arg `TEST_ENABLED=false` on the CLI or in your stack.yml
+# To enable testing, you can set the build_arg `TEST_ENABLED=true` on the CLI or in your stack.yml
 # https://docs.openfaas.com/reference/yaml/#function-build-args-build-args
 
 def test_handle():

template/python3-http-debian/Dockerfile

@@ -42,13 +42,10 @@ RUN pip install --no-cache-dir --user -r requirements.txt
 USER root
 COPY --chown=app:app function/   .
 
-FROM build AS test
-
 ARG TEST_COMMAND=tox
-ARG TEST_ENABLED=true
+ARG TEST_ENABLED=false
 RUN [ "$TEST_ENABLED" = "false" ] && echo "skipping tests" || eval "$TEST_COMMAND"
 
-
 FROM build AS ship
 WORKDIR /home/app/
 

template/python3-http-debian/function/handler_test.py

@@ -2,7 +2,7 @@
 
 # Test your handler here
 
-# To disable testing, you can set the build_arg `TEST_ENABLED=false` on the CLI or in your stack.yml
+# To enable testing, you can set the build_arg `TEST_ENABLED=true` on the CLI or in your stack.yml
 # https://docs.openfaas.com/reference/yaml/#function-build-args-build-args
 
 def test_handle():

template/python3-http/Dockerfile

@@ -41,9 +41,8 @@ RUN pip install --no-cache-dir --user -r requirements.txt
 USER root
 COPY --chown=app:app function/   .
 
-FROM build AS test
 ARG TEST_COMMAND=tox
-ARG TEST_ENABLED=true
+ARG TEST_ENABLED=false
 RUN [ "$TEST_ENABLED" = "false" ] && echo "skipping tests" || eval "$TEST_COMMAND"
 
 FROM build AS ship

template/python3-http/function/handler_test.py

@@ -2,7 +2,7 @@
 
 # Test your handler here
 
-# To disable testing, you can set the build_arg `TEST_ENABLED=false` on the CLI or in your stack.yml
+# To enable testing, you can set the build_arg `TEST_ENABLED=true` on the CLI or in your stack.yml
 # https://docs.openfaas.com/reference/yaml/#function-build-args-build-args
 
 def test_handle():