Update unit test workflow

Author: MislavReversingLabs

.github/workflows/test.yml

@@ -1,11 +1,15 @@
 name: Run unit tests
 
-on: [push]
+on:
+  pull_request:
+    types:
+      - closed
 
 jobs:
   build:
-
+    if: github.event.pull_request.merged
     runs-on: ubuntu-latest
+
     strategy:
       matrix:
         python-version: ['3.7', '3.8', '3.9', '3.10']