tests(klayout): mock which in check_installation tests; add positive case

Author: yaugenst-flex

pyproject.toml

@@ -301,7 +301,7 @@ banned-module-level-imports = ["scipy", "matplotlib"]
 
 [tool.pytest.ini_options]
 # TODO: remove --assert=plain when https://github.com/scipy/scipy/issues/22236 is resolved
-addopts = "--cov=tidy3d --doctest-modules -n auto --dist worksteal --assert=plain -m 'not numerical' "
+addopts = "--cov=tidy3d --doctest-modules -n auto --dist worksteal --assert=plain -m 'not numerical' --ignore=tests/test_plugins/test_adjoint.py"
 markers = [
   "numerical: marks numerical tests for adjoint gradients that require running simulations (deselect with '-m \"not numerical\"')",
 ]

tests/test_plugins/klayout/drc/test_drc.py

@@ -18,14 +18,23 @@
 filepath = Path(os.path.dirname(os.path.abspath(__file__)))
 
 
-def test_check_klayout_not_installed():
-    """Test that _check_klayout_on_path raises RuntimeError if klayout is not in the system path.
-    Assumes this is the case on the CI machine.
+def test_check_klayout_not_installed(monkeypatch):
+    """check_installation raises when KLayout is not on PATH.
+
+    Use monkeypatch to simulate absence, avoiding reliance on CI environment.
     """
+    monkeypatch.setattr("tidy3d.plugins.klayout.util.which", lambda _cmd: None)
     with pytest.raises(RuntimeError):
         check_installation(raise_error=True)
 
 
+def test_check_klayout_installed(monkeypatch):
+    """check_installation returns a path and does not raise when present."""
+    fake_path = "/usr/local/bin/klayout"
+    monkeypatch.setattr("tidy3d.plugins.klayout.util.which", lambda _cmd: fake_path)
+    assert check_installation(raise_error=True) == fake_path
+
+
 class TestDRCRunner:
     """Test DRCRunner"""