diff --git a/.github/workflows/github-ci.yaml b/.github/workflows/github-ci.yaml
index a47241ed6..6ed659f4d 100644
--- a/.github/workflows/github-ci.yaml
+++ b/.github/workflows/github-ci.yaml
@@ -51,8 +51,12 @@ jobs:
     - name: Test with pytest
       run: |
         python -m coverage run --parallel-mode -m pytest Tests -vv
-      if: matrix.python-version != '3.10.1'
-    - name: Test with pytest
+      if: matrix.python-version != '3.10.1' && matrix.python-version != 2.7
+    - name: Test with pytest (2.7)
+      run: |
+        python -m coverage run --parallel-mode -m pytest Tests -vv -m "not no_py27"
+      if: matrix.python-version == 2.7
+    - name: Test with pytest (OO flag)
       run: |
         python -OO -m coverage run --parallel-mode -m pytest Tests -vv
       if: matrix.python-version == '3.10.1'
diff --git a/PyPDF2/filters.py b/PyPDF2/filters.py
index 165dd68ce..44f8b92d9 100644
--- a/PyPDF2/filters.py
+++ b/PyPDF2/filters.py
@@ -40,7 +40,7 @@
 from PyPDF2.constants import ImageAttributes as IA
 from PyPDF2.constants import LzwFilterParameters as LZW
 from PyPDF2.constants import StreamAttributes as SA
-from PyPDF2.errors import PdfReadError
+from PyPDF2.errors import PdfReadError, PdfStreamError
 from PyPDF2.utils import ord_, paethPredictor
 
 if version_info < ( 3, 0 ):
@@ -194,12 +194,26 @@ def encode(data):
 
 
 class ASCIIHexDecode(object):
+    """
+    The ASCIIHexDecode filter decodes data that has been encoded in ASCII
+    hexadecimal form into a base-7 ASCII format.
+    """
+
     @staticmethod
     def decode(data, decodeParms=None):
+        """
+        :param data: a str sequence of hexadecimal-encoded values to be
+            converted into a base-7 ASCII string
+        :param decodeParms:
+        :return: a string conversion in base-7 ASCII, where each of its values
+            v is such that 0 <= ord(v) <= 127.
+        """
         retval = ""
         char = ""
         x = 0
         while True:
+            if x >= len(data):
+                raise PdfStreamError("Unexpected EOD in ASCIIHexDecode")
             c = data[x]
             if c == ">":
                 break
diff --git a/Tests/test_filters.py b/Tests/test_filters.py
new file mode 100644
index 000000000..ada1db4a2
--- /dev/null
+++ b/Tests/test_filters.py
@@ -0,0 +1,59 @@
+from PyPDF2.filters import ASCIIHexDecode
+import string
+from PyPDF2.errors import PdfStreamError
+import pytest
+
+
+@pytest.mark.parametrize(
+    "input,expected",
+    [
+        (">", ""),
+        (
+            "6162636465666768696a6b6c6d6e6f707172737475767778797a>",
+            string.ascii_lowercase,
+        ),
+        (
+            "4142434445464748494a4b4c4d4e4f505152535455565758595a>",
+            string.ascii_uppercase,
+        ),
+        (
+            "6162636465666768696a6b6c6d6e6f707172737475767778797a4142434445464748494a4b4c4d4e4f505152535455565758595a>",
+            string.ascii_letters,
+        ),
+        ("30313233343536373839>", string.digits),
+        (
+            "3  031323334353637   3839>",
+            string.digits,
+        ),  # Same as previous, but whitespaced
+        ("30313233343536373839616263646566414243444546>", string.hexdigits),
+        ("20090a0d0b0c>", string.whitespace),
+    ],
+    ids=[
+        "empty",
+        "ascii_lowercase",
+        "ascii_uppercase",
+        "ascii_letters",
+        "digits",
+        "digits_whitespace",
+        "hexdigits",
+        "whitespace",
+    ],
+)
+@pytest.mark.no_py27
+def test_expected_results(input, expected):
+    """
+    Feeds a bunch of values to ASCIIHexDecode.decode() and ensures the
+    correct output is returned.
+    TO-DO What is decode() supposed to do for such inputs as ">>", ">>>" or
+    any other not terminated by ">"? (For the latter case, an exception
+    is currently raised.)
+    """
+
+    assert ASCIIHexDecode.decode(input) == expected
+
+
+def test_no_eod():
+    """Ensuring an exception is raised when no EOD character is present"""
+    with pytest.raises(PdfStreamError) as exc:
+        ASCIIHexDecode.decode("")
+    assert exc.value.args[0] == "Unexpected EOD in ASCIIHexDecode"
diff --git a/pytest.ini b/pytest.ini
new file mode 100644
index 000000000..c7afa9968
--- /dev/null
+++ b/pytest.ini
@@ -0,0 +1,3 @@
+[pytest]
+markers =
+    no_py27: Flag for tests that fail under Python 2.7 only
\ No newline at end of file