CI: test installation.

.github/workflows/ci.yml

@@ -22,13 +22,30 @@ jobs:
         apt-get update
         apt-get install -y python3-gi-cairo gir1.2-pango-1.0
         apt-get install -y make perl
+    - name: set up PATH
+      run: |
+        PATH="$PATH:$HOME/.local/bin"
+        echo "$PATH" >> $GITHUB_PATH
     - name: check Python version
       run: |
         python3 --version
     - name: run tests
       run: |
         export LC_ALL=C.UTF-8
         make test verbose=1
+    - name: install
+      run: |
+        make install PREFIX=~/.local
+    - name: check whether the executable was installed correctly
+      run: |
+        cd /
+        ubanner --help
+    - name: run post-install tests
+      run: |
+        mv ubanner ubanner.bak
+        export LC_ALL=C.UTF-8
+        make test-installed verbose=1
+        mv ubanner.bak ubanner
 
   static:
     runs-on: ${{matrix.os}}