ci: run offline tests in offline environment

Signed-off-by: Facundo Tuesca <facundo.tuesca@trailofbits.com>

Author: facutuesca

.github/workflows/tests.yml

@@ -53,5 +53,10 @@ jobs:
           cache-dependency-path: pyproject.toml
           allow-prereleases: true
 
-      - name: test
-        run: TEST_OFFLINE=1 make test-nocoverage INSTALL_EXTRA=test
+      - name: install firejail
+        run: sudo apt-get install -y firejail
+
+      - name: run tests offline
+        run: |
+          make dev INSTALL_EXTRA=test
+          firejail --noprofile --net=none --env=TEST_OFFLINE=1 make test-nocoverage