test: add assertion to inspect image

Author: natthan-pigoux

tests/test_singularity.py

@@ -6,6 +6,7 @@
 import pytest
 
 from cwltool.main import main
+from cwltool.singularity import _inspect_singularity_image
 
 from .util import (
     get_data,
@@ -178,8 +179,13 @@ def test_singularity_local_sandbox_image(tmp_path: Path):
             container_path / "alpine",
             "docker://alpine:latest",
         ]
+
         build = subprocess.run(cmd, capture_output=True, text=True)
         if build.returncode == 0:
+            # Verify the path is a container image
+            res_inspect = _inspect_singularity_image(container_path / "alpine")
+            assert res_inspect is True
+
             result_code, stdout, stderr = get_main_output(
                 [
                     "--singularity",