patchtest2/tests: add diff parsing test

There's lots of room to improve here, but this provides a basic means of
trying to parse a diff and reporting which commit failed that test.

Signed-off-by: Trevor Gamblin <[email protected]>

Author: threexc

src/patchtest2/mbox.py

@@ -48,6 +48,7 @@ def __next__(self):
 
 class Patch:
     def __init__(self, data):
+        self.data = data
         self.author = data["From"]
         self.to = data["To"]
         self.cc = data["Cc"]

src/patchtest2/tests/core.py

@@ -1,6 +1,7 @@
 import patchtest2.patterns as patterns
 import pyparsing
 import re
+import unidiff
 
 
 class PatchtestResult:
@@ -39,6 +40,10 @@ def __init__(self, target_repo, series):
                     "has_commit_message",
                     self._results(test_mbox_has_commit_message),
                 ),
+                (
+                    "diff_parse",
+                    self._results(test_mbox_unidiff_parse_error),
+                ),
             ]
         )
 
@@ -123,3 +128,15 @@ def test_mbox_has_commit_message(target):
         result = "FAIL"
 
     return PatchtestResult(target.subject, test_name, result, reason)
+
+def test_mbox_unidiff_parse_error(target):
+    test_name = "test_mbox_unidiff_parse_error"
+    result = "PASS"
+    reason = f"Patch \"{target.shortlog}\" contains malformed diff lines."
+
+    try:
+        diff = unidiff.PatchSet.from_string(target.data.as_string())
+    except unidiff.UnidiffParseError as upe:
+        result = "FAIL"
+
+    return PatchtestResult(target.subject, test_name, result, reason)