1 files changed, 46 insertions, 4 deletions
diff --git a/tests/try_execfile.py b/tests/try_execfile.py
index 825fdb70..1035dff9 100644
--- a/tests/try_execfile.py
+++ b/tests/try_execfile.py
@@ -1,6 +1,48 @@
-"""Test file for run_python_file."""
+"""Test file for run_python_file.
 
-import os, pprint, sys
+This file is executed two ways::
+
+    $ coverage run try_execfile.py
+
+and::
+
+    $ python try_execfile.py
+
+The output is compared to see that the program execution context is the same
+under coverage and under Python.
+
+It is not crucial that the execution be identical, there are some differences
+that are OK.  This program canonicalizes the output to gloss over those
+differences and get a clean diff.
+
+"""
+
+import json, os, sys
+
+# sys.path varies by execution environments.  Coverage.py uses setuptools to
+# make console scripts, which means pkg_resources is imported.  pkg_resources
+# removes duplicate entries from sys.path.  So we do that too, since the extra
+# entries don't affect the running of the program.
+
+def same_file(p1, p2):
+    """Determine if `p1` and `p2` refer to the same existing file."""
+    if not p1:
+        return not p2
+    if not os.path.exists(p1):
+        return False
+    if not os.path.exists(p2):
+        return False
+    return os.path.samefile(p1, p2)
+
+def without_same_files(filenames):
+    """Return the list `filenames` with duplicates (by same_file) removed."""
+    reduced = []
+    for filename in filenames:
+        if not any(same_file(filename, other) for other in reduced):
+            reduced.append(filename)
+    return reduced
+
+cleaned_sys_path = [os.path.normcase(p) for p in without_same_files(sys.path)]
 
 DATA = "xyzzy"
 
@@ -23,7 +65,7 @@ globals_to_check = {
     'FN_VAL': FN_VAL,
     '__main__.DATA': getattr(__main__, "DATA", "nothing"),
     'argv': sys.argv,
-    'path': [os.path.normcase(p) for p in sys.path],
+    'path': cleaned_sys_path,
 }
 
-pprint.pprint(globals_to_check)
+print(json.dumps(globals_to_check))