diff --git a/test/unit/webdriver/errorhandler_test.py b/test/unit/webdriver/errorhandler_test.py
new file mode 100644
index 00000000..f5220156
--- /dev/null
+++ b/test/unit/webdriver/errorhandler_test.py
@@ -0,0 +1,67 @@
+import pytest
+
+from appium.webdriver.errorhandler import format_stacktrace
+
+
+class TestFormatStacktrace:
+    @pytest.mark.parametrize(
+        ('input_data', 'expected'),
+        [
+            (None, []),
+            ('', []),
+            ([], []),
+            ({}, []),
+        ],
+    )
+    def test_format_stacktrace_empty(self, input_data: None | str | list | dict, expected: list[str]) -> None:
+        assert format_stacktrace(input_data) == expected
+
+    def test_format_stacktrace_string(self) -> None:
+        stack = 'Error: Something went wrong\n    at foo (file.js:10)\n    at bar (file.js:20)'
+        expected = [
+            'Error: Something went wrong',
+            '    at foo (file.js:10)',
+            '    at bar (file.js:20)',
+        ]
+        assert format_stacktrace(stack) == expected
+
+    def test_format_stacktrace_sequence_dicts(self) -> None:
+        frames = [
+            {
+                'lineNumber': 42,
+                'fileName': 'index.js',
+                'methodName': 'handleClick',
+                'className': 'MyComponent',
+            },
+            {
+                'fileName': 'utils.js',
+                'methodName': 'helper',
+            },
+            {},
+        ]
+        expected = [
+            '    at MyComponent.handleClick (index.js:42)',
+            '    at helper (utils.js)',
+            '    at <anonymous> (<anonymous>)',
+        ]
+        assert format_stacktrace(frames) == expected
+
+    def test_format_stacktrace_sequence_with_non_dict_elements(self) -> None:
+        frames = [
+            'not a dict',
+            123,
+            None,
+            {
+                'lineNumber': 5,
+                'fileName': 'main.py',
+                'methodName': 'run',
+            },
+        ]
+        expected = [
+            '    at run (main.py:5)',
+        ]
+        assert format_stacktrace(frames) == expected
+
+    def test_format_stacktrace_non_iterable_type_error(self) -> None:
+        assert format_stacktrace(123) == []
+        assert format_stacktrace(True) == []