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diff --git a/bs4/tests/test_fuzz.py b/bs4/tests/test_fuzz.py
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+"""This file contains test cases reported by third parties using
+fuzzing tools, primarily from Google's oss-fuzz project. Some of these
+represent real problems with Beautiful Soup, but many are problems in
+libraries that Beautiful Soup depends on, and many of the test cases
+represent different ways of triggering the same problem.
+
+Grouping these test cases together makes it easy to see which test
+cases represent the same problem, and puts the test cases in close
+proximity to code that can trigger the problems.
+"""
+import os
+import pytest
+from bs4 import (
+    BeautifulSoup,
+    ParserRejectedMarkup,
+)
+
+class TestFuzz(object):
+
+    # This class of error has been fixed by catching a less helpful
+    # exception from html.parser and raising ParserRejectedMarkup
+    # instead.
+    @pytest.mark.parametrize(
+        "filename", [
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-5703933063462912",
+        ]
+    )
+    def test_rejected_markup(self, filename):
+        markup = self.__markup(filename)
+        with pytest.raises(ParserRejectedMarkup):
+            BeautifulSoup(markup, 'html.parser')
+
+    # This class of error has to do with very deeply nested documents
+    # which overflow the Python call stack when the tree is converted
+    # to string. This is an issue with Beautiful Soup. See
+    # [bug=1471755], for example.
+    @pytest.mark.skip("recursion limit exceeded")
+    @pytest.mark.parametrize(
+        "filename", [
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-5984173902397440",
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-5167584867909632",
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-5984173902397440",
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-6124268085182464",
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-6450958476902400",
+        ]
+    )
+    def test_recursion_limit_exceeded(self, filename):
+        markup = self.__markup(filename)
+        with pytest.raises(RecursionError):
+            BeautifulSoup(markup, 'html.parser').encode()
+
+    # This class of error represents problems with html5lib's parser,
+    # not Beautiful Soup.
+    @pytest.mark.skip("html5lib problems")
+    @pytest.mark.parametrize(
+        "filename", [
+            # b"""ÿ<!DOCTyPEV PUBLIC'''Ð'"""
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-4818336571064320",
+
+            # b')<a><math><TR><a><mI><a><p><a>'
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-4999465949331456",
+
+            # very large, lots of %&&%&&
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-5389523868581888",
+
+            # b'-<math><sElect><mi><sElect><sElect>'
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-5843991618256896",
+
+            # b'ñ<table><svg><html>'
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-6241471367348224",
+
+            # <TABLE>, some ^@ characters, some <math> tags.
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-6600557255327744"
+        ]
+    )
+    def test_html5lib_parse_errors(self, filename):
+        markup = self.__markup(filename)
+        print(BeautifulSoup(markup, 'html5lib').encode())
+
+    def __markup(self, filename):
+        this_dir = os.path.split(__file__)[0]
+        path = os.path.join(this_dir, 'fuzz', filename)
+        return open(path, 'rb').read()