Increase testability of shell scripts (#752)

This is a preparation for #724 (bash script testing) which would be too complex to review if done there.

Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/752
Co-authored-by: justusbunsi <sk.bunsenbrenner@gmail.com>
Co-committed-by: justusbunsi <sk.bunsenbrenner@gmail.com>

unittests/helm/deployment/basic.yaml

@@ -29,3 +29,19 @@ tests:
           path: spec.template.metadata.labels
           content:
             hello: world
+  - it: "injects TMP_EXISTING_ENVS_FILE as environment variable to 'init-app-ini' init container"
+    template: templates/gitea/deployment.yaml
+    asserts:
+      - contains:
+          path: spec.template.spec.initContainers[1].env
+          content:
+            name: TMP_EXISTING_ENVS_FILE
+            value: /tmp/existing-envs
+  - it: "injects ENV_TO_INI_MOUNT_POINT as environment variable to 'init-app-ini' init container"
+    template: templates/gitea/deployment.yaml
+    asserts:
+      - contains:
+          path: spec.template.spec.initContainers[1].env
+          content:
+            name: ENV_TO_INI_MOUNT_POINT
+            value: /env-to-ini-mounts