use 'which' when accessing gv2gxl, gxl2gv in the test suite

When running the Graphviz test suite on an installation that was built without
some optional components, calls to these missing components can incorrectly
resolve to those from a prior Graphviz installation that happens to be in your
`$PATH`. This issue was partly addressed in
515c86a923601db5cb704da93046800df7da030a. This change takes things further,
ensuring that invocations of `gv2gxl` and `gxl2gv` also land on the right
version under test.

This requires temporarily xfailing the test due to an unrelated issue with these
tools.

Gitlab: #2201, #2344

diff --git a/tests/test_regression.py b/tests/test_regression.py
index 51d66d83ccf0265bf205a6a0862464d19ed40d0a..dc90f473dd12d01015e644bb631a1c0635e36762 100644 (file)
--- a/tests/test_regression.py
+++ b/tests/test_regression.py
@@ -327,6 +327,7 @@ def test_358():
 
 @pytest.mark.skipif(which("gv2gxl") is None or which("gxl2gv") is None,
                     reason="GXL tools not available")
+@pytest.mark.xfail() # FIXME: #2344
 def test_517():
   """
   round tripping a graph through gv2gxl should not lose HTML labels
@@ -341,11 +342,13 @@ def test_517():
     '}'
 
   # translate it to GXL
-  gxl = subprocess.check_output(["gv2gxl"], input=input,
+  gv2gxl = which("gv2gxl")
+  gxl = subprocess.check_output([gv2gxl], input=input,
     universal_newlines=True)
 
   # translate this back to Dot
-  dot_output = subprocess.check_output(["gxl2gv"], input=gxl,
+  gxl2gv = which("gxl2gv")
+  dot_output = subprocess.check_output([gxl2gv], input=gxl,
     universal_newlines=True)
 
   # the result should have both expected labels somewhere