use a virtual environment for unit tests

.github/workflows/unit-tests.yml

@@ -2,8 +2,8 @@ name: Unit tests
 
 on:
   push:
-    branches:
-      - master
+      #branches:
+      #- master
     paths:
       - .github/workflows/unit-tests.yml
       - arver/**
@@ -26,7 +26,7 @@ jobs:
 
     strategy:
       matrix:
-        python-version: ['3.7', '3.8', '3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.7', '3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
 
     steps:
     - name: Check out repository
@@ -46,17 +46,13 @@ jobs:
       run: |
         sudo apt-get install -y libsndfile-dev
 
-    - name: Install ARver dependencies from PyPI
-      run: |
-        python3 --version
-        python3 -m pip install --upgrade pip
-        pip3 install setuptools
-        pip3 install -r requirements.txt
-        pip3 list
-
-    - name: Build C extension
+    - name: Build and install ARver in a virtual environment
       run: |
-        make ext
+        python3 -m venv --clear .venv
+        source .venv/bin/activate
+        pip3 --version
+        pip3 install .
+        arver --version
 
     - name: Run unit tests
       run: |