Read class properties & call methods to cover more features

Property access and private methods on the `Diff` class are complex and involve encoding and decoding operations that warrant being tested. This test borrows its design from the `test_diff.py` unit test file.

Author: DaveLak

fuzzing/fuzz-targets/fuzz_diff.py

@@ -1,5 +1,6 @@
 importsys
 importos
+importio
 importtempfile
 frombinasciiimportErrorasBinasciiError
 
@@ -13,13 +14,26 @@
 fromgitimportRepo, Diff
 
 
+classBytesProcessAdapter:
+"""Allows bytes to be used as process objects returned by subprocess.Popen."""
+
+def__init__(self, input_string):
+self.stdout=io.BytesIO(input_string)
+self.stderr=io.BytesIO()
+
+defwait(self):
+return0
+
+poll=wait
+
+
 defTestOneInput(data):
 fdp=atheris.FuzzedDataProvider(data)
 
 withtempfile.TemporaryDirectory() astemp_dir:
 repo=Repo.init(path=temp_dir)
 try:
-Diff(
+diff=Diff(
 repo,
 a_rawpath=fdp.ConsumeBytes(fdp.ConsumeIntInRange(0, fdp.remaining_bytes())),
 b_rawpath=fdp.ConsumeBytes(fdp.ConsumeIntInRange(0, fdp.remaining_bytes())),
@@ -44,6 +58,21 @@ def TestOneInput(data):
 else:
 raisee
 
+_=diff.__str__()
+_=diff.a_path
+_=diff.b_path
+_=diff.rename_from
+_=diff.rename_to
+_=diff.renamed_file
+
+diff_index=diff._index_from_patch_format(
+repo, proc=BytesProcessAdapter(fdp.ConsumeBytes(fdp.ConsumeIntInRange(0, fdp.remaining_bytes())))
+ )
+
+diff._handle_diff_line(
+lines_bytes=fdp.ConsumeBytes(fdp.ConsumeIntInRange(0, fdp.remaining_bytes())), repo=repo, index=diff_index
+ )
+
 
 defmain():
 atheris.Setup(sys.argv, TestOneInput)