test: correct syntax for verify tasks, make them idempotent, run them only on...

test: correct syntax for verify tasks, make them idempotent, run them only on the Rosetta Molecule VM

molecule/resources/playbooks/verify.yml

@@ -3,25 +3,42 @@
 
 - name: Verify
   hosts: all
-  gather_facts: true
+  gather_facts: false
   tasks:
     - name: Example assertion
       ansible.builtin.assert:
         that: true
+
 - name: Run Rosetta-specific tests.
-      when: "{{ ansible_hostname }} = 'vm-rosapp-mol'"
-      block:
+  hosts: 'vm-rosapp-mol'
+  gather_facts: true
+  tasks:
     - name: Get list of installed MediaArea packages.
       ansible.builtin.command:
         cmd: "dnf list mediaconch mediainfo libmediainfo libzen"
       register: mediaconch_repo
-        - name: Test if the MediaArea packages are installed from their own repository.
+      changed_when: false
+    - name: >
+        Test if the MediaArea packages are installed from their own repository.
       ansible.builtin.assert:
-            that: "'@MediaArea' in {{ mediaconch_repo.stdout }}"
+        that: "'@MediaArea' in mediaconch_repo.stdout"
+        success_msg: >
+          The string '@MediaArea' was found in the list of installed MediaArea
+          packages, so we can assume that at least one of them was installed
+          from the official MediaArea repository.
+        fail_msg: >
+          The string '@MediaArea' was NOT found in the list of installed
+          MediaArea packages, so they are probably installed from another
+          source, quite possibly EPEL. These will probably not work without
+          RHEL 8.
+
     - name: Call mediaconch to see if it runs without errors.
       ansible.builtin.command:
         cmd: "mediaconch -h"
       register: mediaconch_output
+      changed_when: false
     - name: Parse mediaconch output.
       ansible.builtin.assert:
-            that: "'MediaConch Command Line Interface' in {{ mediaconch_output.stdout }}"
+        that: "'MediaConch Command Line Interface' in mediaconch_output.stdout"
+        success_msg: MediaConch runs as expected.
+        fail_msg: MediaConch couldn't be run without errors.