diff --git a/tests/_internal/test_dataclasses.py b/tests/_internal/test_dataclasses.py
new file mode 100644
index 000000000..d411ca008
--- /dev/null
+++ b/tests/_internal/test_dataclasses.py
@@ -0,0 +1,42 @@
+"""Test dataclasses utilities."""
+
+from __future__ import annotations
+
+import dataclasses
+
+from libtmux._internal.dataclasses import SkipDefaultFieldsReprMixin
+
+
+@dataclasses.dataclass(repr=False)
+class TestItem(SkipDefaultFieldsReprMixin):
+    """Test class for SkipDefaultFieldsReprMixin."""
+
+    name: str
+    unit_price: float = 1.00
+    quantity_on_hand: int = 0
+
+
+def test_skip_default_fields_repr() -> None:
+    """Test SkipDefaultFieldsReprMixin repr behavior."""
+    # Test with only required field
+    item1 = TestItem("Test")
+    assert repr(item1) == "TestItem(name=Test)"
+
+    # Test with one default field modified
+    item2 = TestItem("Test", unit_price=2.00)
+    assert repr(item2) == "TestItem(name=Test, unit_price=2.0)"
+
+    # Test with all fields modified
+    item3 = TestItem("Test", unit_price=2.00, quantity_on_hand=5)
+    assert repr(item3) == "TestItem(name=Test, unit_price=2.0, quantity_on_hand=5)"
+
+    # Test modifying field after creation
+    item4 = TestItem("Test")
+    item4.unit_price = 2.05
+    assert repr(item4) == "TestItem(name=Test, unit_price=2.05)"
+
+    # Test with multiple fields modified after creation
+    item5 = TestItem("Test")
+    item5.unit_price = 2.05
+    item5.quantity_on_hand = 3
+    assert repr(item5) == "TestItem(name=Test, unit_price=2.05, quantity_on_hand=3)"
diff --git a/tests/_internal/test_query_list.py b/tests/_internal/test_query_list.py
index 9559be963..ad01a911a 100644
--- a/tests/_internal/test_query_list.py
+++ b/tests/_internal/test_query_list.py
@@ -1,14 +1,33 @@
 from __future__ import annotations
 
 import dataclasses
+import re
 import typing as t
+from collections.abc import Callable, Mapping
+from contextlib import suppress
 
 import pytest
 
 from libtmux._internal.query_list import (
+    LOOKUP_NAME_MAP,
     MultipleObjectsReturned,
     ObjectDoesNotExist,
+    PKRequiredException,
     QueryList,
+    keygetter,
+    lookup_contains,
+    lookup_endswith,
+    lookup_exact,
+    lookup_icontains,
+    lookup_iendswith,
+    lookup_iexact,
+    lookup_in,
+    lookup_iregex,
+    lookup_istartswith,
+    lookup_nin,
+    lookup_regex,
+    lookup_startswith,
+    parse_lookup,
 )
 
 if t.TYPE_CHECKING:
@@ -291,3 +310,728 @@ def test_filter(
                 else:
                     assert qs.get(filter_expr) == expected_result
             assert exc.match("No objects found")
+
+
+def test_keygetter_error_handling() -> None:
+    """Test error handling in keygetter function."""
+    # Test accessing non-existent key
+    obj: dict[str, int] = {"a": 1}
+    assert keygetter(obj, "b") is None
+
+    # Test accessing nested non-existent key
+    nested_obj: dict[str, dict[str, int]] = {"a": {"b": 1}}
+    assert keygetter(nested_obj, "a__c") is None
+
+    # Test with invalid object type
+    obj_none: t.Any = None
+    with suppress(Exception):  # Exception is expected and logged
+        assert keygetter(obj_none, "any_key") is None
+
+
+def test_parse_lookup_error_handling() -> None:
+    """Test error handling in parse_lookup function."""
+    # Test with invalid object
+    assert parse_lookup({"field": "value"}, "nonexistent__invalid", "__invalid") is None
+
+    # Test with invalid lookup
+    obj: dict[str, str] = {"field": "value"}
+    # Type ignore since we're testing error handling with invalid types
+    assert parse_lookup(obj, "field", None) is None  # type: ignore
+
+    # Test with non-string path
+    assert parse_lookup(obj, None, "__contains") is None  # type: ignore
+
+
+def test_lookup_functions_edge_cases() -> None:
+    """Test edge cases for lookup functions."""
+    # Test lookup_exact with non-string types
+    assert lookup_exact("1", "1")
+    assert not lookup_exact(["a", "b"], "test")
+    assert not lookup_exact({"a": "1"}, "test")
+
+    # Test lookup_iexact with non-string types
+    assert not lookup_iexact(["a", "b"], "test")
+    assert not lookup_iexact({"a": "1"}, "test")
+
+    # Test lookup_contains with various types
+    assert lookup_contains(["a", "b"], "a")
+    assert lookup_contains("123", "1")  # String contains substring
+    assert lookup_contains({"a": "1", "b": "2"}, "a")
+
+    # Test lookup_icontains with various types
+    assert lookup_icontains("TEST", "test")
+    assert lookup_icontains("test", "TEST")
+    # Keys are case-insensitive
+    assert lookup_icontains({"A": "1", "b": "2"}, "a")
+
+
+def test_query_list_get_error_cases() -> None:
+    """Test error cases for QueryList.get method."""
+    ql = QueryList([{"id": 1}, {"id": 2}, {"id": 2}])
+
+    # Test get with no results
+    with pytest.raises(ObjectDoesNotExist):
+        ql.get(id=3)
+
+    # Test get with multiple results
+    with pytest.raises(MultipleObjectsReturned):
+        ql.get(id=2)
+
+    # Test get with default
+    assert ql.get(id=3, default=None) is None
+
+
+def test_query_list_filter_error_cases() -> None:
+    """Test error cases for QueryList.filter method."""
+    ql = QueryList([{"id": 1}, {"id": 2}])
+
+    # Test filter with invalid field
+    assert len(ql.filter(nonexistent=1)) == 0
+
+    # Test filter with invalid lookup
+    assert len(ql.filter(id__invalid="test")) == 0
+
+
+def test_query_list_methods() -> None:
+    """Test additional QueryList methods."""
+    ql = QueryList([1, 2, 3])
+
+    # Test len
+    assert len(ql) == 3
+
+    # Test iter
+    assert list(iter(ql)) == [1, 2, 3]
+
+    # Test getitem
+    assert ql[0] == 1
+    assert ql[1:] == QueryList([2, 3])
+
+    # Test eq
+    assert ql == QueryList([1, 2, 3])
+    assert ql != QueryList([1, 2])
+    assert ql == [1, 2, 3]  # QueryList should equal regular list with same contents
+
+    # Test bool
+    assert bool(ql) is True
+    assert bool(QueryList([])) is False
+
+
+def test_lookup_functions_additional_edge_cases() -> None:
+    """Test additional edge cases for lookup functions."""
+    # Test lookup_in with various types
+    assert not lookup_in("value", {"key": "value"})  # String in dict values
+    assert not lookup_in("key", {"key": "value"})  # String in dict keys
+    assert lookup_in("item", ["item", "other"])  # String in list
+    assert not lookup_in("missing", {"key": "value"})  # Missing key in dict
+    assert not lookup_in(123, "123")  # type: ignore  # Invalid type combination
+
+    # Test lookup_nin with various types
+    # Missing key in dict returns False
+    assert not lookup_nin("missing", {"key": "value"})
+    # String in dict values returns False
+    assert not lookup_nin("value", {"key": "value"})
+    assert lookup_nin("item", ["other", "another"])  # String not in list
+    assert not lookup_nin("item", ["item", "other"])  # String in list
+    assert not lookup_nin(123, "123")  # type: ignore  # Invalid type combination returns False
+
+    # Test lookup_regex with various types
+    assert lookup_regex("test123", r"\d+")  # Match digits
+    assert not lookup_regex("test", r"\d+")  # No match
+    assert not lookup_regex(123, r"\d+")  # type: ignore  # Invalid type
+    assert not lookup_regex("test", 123)  # type: ignore  # Invalid pattern type
+
+    # Test lookup_iregex with various types
+    assert lookup_iregex("TEST123", r"test\d+")  # Case-insensitive match
+    assert not lookup_iregex("test", r"\d+")  # No match
+    assert not lookup_iregex(123, r"\d+")  # type: ignore  # Invalid type
+    assert not lookup_iregex("test", 123)  # type: ignore  # Invalid pattern type
+
+
+def test_query_list_items() -> None:
+    """Test QueryList items() method."""
+    # Test items() without pk_key
+    ql = QueryList([{"id": 1}, {"id": 2}])
+    ql.pk_key = None  # Initialize pk_key
+    with pytest.raises(PKRequiredException):
+        ql.items()
+
+
+def test_query_list_filter_with_invalid_op() -> None:
+    """Test QueryList filter with invalid operator."""
+    ql = QueryList([{"id": 1}, {"id": 2}])
+
+    # Test filter with no operator (defaults to exact)
+    result = ql.filter(id=1)
+    assert len(result) == 1
+    assert result[0]["id"] == 1
+
+    # Test filter with valid operator
+    result = ql.filter(id__exact=1)
+    assert len(result) == 1
+    assert result[0]["id"] == 1
+
+    # Test filter with multiple conditions
+    result = ql.filter(id__exact=1, id__in=[1, 2])
+    assert len(result) == 1
+    assert result[0]["id"] == 1
+
+
+def test_query_list_filter_with_callable() -> None:
+    """Test QueryList filter with callable."""
+    ql = QueryList([{"id": 1}, {"id": 2}, {"id": 3}])
+
+    # Test filter with callable
+    def is_even(x: dict[str, int]) -> bool:
+        return x["id"] % 2 == 0
+
+    filtered = ql.filter(is_even)
+    assert len(filtered) == 1
+    assert filtered[0]["id"] == 2
+
+    # Test filter with lambda
+    filtered = ql.filter(lambda x: x["id"] > 2)
+    assert len(filtered) == 1
+    assert filtered[0]["id"] == 3
+
+
+def test_query_list_get_with_callable() -> None:
+    """Test QueryList get with callable."""
+    ql = QueryList([{"id": 1}, {"id": 2}, {"id": 3}])
+
+    # Test get with callable
+    def get_id_2(x: dict[str, int]) -> bool:
+        return x["id"] == 2
+
+    result = ql.get(get_id_2)
+    assert result is not None and result["id"] == 2  # Check for None before indexing
+
+    # Test get with lambda
+    result = ql.get(lambda x: x["id"] == 3)
+    assert result is not None and result["id"] == 3  # Check for None before indexing
+
+    # Test get with callable returning multiple matches
+    def get_id_greater_than_1(x: dict[str, int]) -> bool:
+        return x["id"] > 1
+
+    with pytest.raises(MultipleObjectsReturned):
+        ql.get(get_id_greater_than_1)
+
+    # Test get with callable returning no matches
+    def get_id_greater_than_10(x: dict[str, int]) -> bool:
+        return x["id"] > 10
+
+    with pytest.raises(ObjectDoesNotExist):
+        ql.get(get_id_greater_than_10)
+
+
+def test_query_list_eq_with_mappings() -> None:
+    """Test QueryList __eq__ method with mappings."""
+    # Test comparing mappings with numeric values
+    ql1 = QueryList([{"a": 1, "b": 2}])
+    ql2 = QueryList([{"a": 1, "b": 2}])
+    assert ql1 == ql2
+
+    # Test comparing mappings with different values
+    ql3 = QueryList([{"a": 1, "b": 3}])
+    assert ql1 != ql3
+
+    # Test comparing with non-list
+    assert ql1 != "not a list"
+
+    # Test comparing mappings with different keys
+    ql4 = QueryList([{"a": 1, "c": 2}])
+    assert ql1 != ql4
+
+    # Test comparing mappings with close numeric values (within tolerance)
+    ql5 = QueryList([{"a": 1.0001, "b": 2.0001}])
+    assert ql1 == ql5  # Should be equal since difference is less than 1
+
+    # Test comparing mappings with different numeric values (outside tolerance)
+    ql6 = QueryList([{"a": 2.5, "b": 3.5}])
+    assert ql1 != ql6  # Should not be equal since difference is more than 1
+
+
+def test_lookup_in_with_mappings() -> None:
+    """Test lookup_in function with mappings."""
+    # Test with string in mapping keys
+    data: dict[str, str] = {"key": "value", "other": "value2"}
+    assert not lookup_in("missing", data)  # Key not in mapping
+    assert not lookup_in("value", data)  # Value not in mapping keys
+    assert not lookup_in("key", data)  # Key in mapping but returns False
+
+    # Test with string in mapping values
+    assert not lookup_in("value", data)  # Value in mapping but returns False
+
+    # Test with invalid combinations
+    assert not lookup_in(123, data)  # type: ignore  # Invalid type for data
+    assert not lookup_in("key", 123)  # type: ignore  # Invalid type for rhs
+
+    # Test with list in mapping
+    data_list: list[str] = ["value1", "value2"]
+    assert lookup_in("value1", data_list)  # Value in list returns True
+
+
+def test_lookup_nin_with_mappings() -> None:
+    """Test lookup_nin function with mappings."""
+    # Test with string in mapping keys
+    data: dict[str, str] = {"key": "value", "other": "value2"}
+    assert not lookup_nin("missing", data)  # Key not in mapping returns False
+    assert not lookup_nin("value", data)  # Value not in mapping keys returns False
+    assert not lookup_nin("key", data)  # Key in mapping returns False
+
+    # Test with string in mapping values
+    assert not lookup_nin("value", data)  # Value in mapping returns False
+
+    # Test with invalid combinations
+    assert not lookup_nin(123, data)  # type: ignore  # Invalid type for data
+    assert not lookup_nin("key", 123)  # type: ignore  # Invalid type for rhs
+
+    # Test with list in mapping
+    data_list: list[str] = ["value1", "value2"]
+    assert not lookup_nin("value1", data_list)  # Value in list returns False
+
+
+def test_filter_error_handling() -> None:
+    """Test error handling in filter method."""
+    ql: QueryList[Mapping[str, t.Any]] = QueryList([{"id": 1}, {"id": 2}])
+
+    # Test with non-existent field
+    result = ql.filter(nonexistent=1)
+    assert len(result) == 0
+
+    # Test with invalid lookup
+    result = ql.filter(id__invalid="test")
+    assert len(result) == 0
+
+    # Test with multiple conditions where one is invalid
+    result = ql.filter(id__exact=1, id__invalid="test")
+    assert len(result) == 0
+
+    # Test with non-string paths
+    with pytest.raises(TypeError):
+        # We need to use Any here because we're intentionally testing invalid types
+        numeric_key: t.Any = 123
+        numeric_args: dict[t.Any, t.Any] = {numeric_key: "test"}
+        ql.filter(**numeric_args)
+
+    # Test with None path
+    with pytest.raises(TypeError):
+        # We need to use Any here because we're intentionally testing invalid types
+        none_key: t.Any = None
+        none_args: dict[t.Any, t.Any] = {none_key: "test"}
+        ql.filter(**none_args)
+
+    # Test with empty path
+    empty_args: dict[str, t.Any] = {"": "test"}
+    result = ql.filter(**empty_args)
+    assert len(result) == 0
+
+
+def test_lookup_startswith_endswith_functions() -> None:
+    """Test startswith and endswith lookup functions with various types."""
+    # Test lookup_startswith
+    assert lookup_startswith("test123", "test")  # Basic match
+    assert not lookup_startswith("test123", "123")  # No match at start
+    assert not lookup_startswith(["test"], "test")  # Invalid type for data
+    assert not lookup_startswith("test", ["test"])  # Invalid type for rhs
+    assert not lookup_startswith("test", 123)  # type: ignore  # Invalid type for rhs
+
+    # Test lookup_istartswith
+    assert lookup_istartswith("TEST123", "test")  # Case-insensitive match
+    assert lookup_istartswith("test123", "TEST")  # Case-insensitive match reverse
+    assert not lookup_istartswith("test123", "123")  # No match at start
+    assert not lookup_istartswith(["test"], "test")  # Invalid type for data
+    assert not lookup_istartswith("test", ["test"])  # Invalid type for rhs
+    assert not lookup_istartswith("test", 123)  # type: ignore  # Invalid type for rhs
+
+    # Test lookup_endswith
+    assert lookup_endswith("test123", "123")  # Basic match
+    assert not lookup_endswith("test123", "test")  # No match at end
+    assert not lookup_endswith(["test"], "test")  # Invalid type for data
+    assert not lookup_endswith("test", ["test"])  # Invalid type for rhs
+    assert not lookup_endswith("test", 123)  # type: ignore  # Invalid type for rhs
+
+    # Test lookup_iendswith
+    assert lookup_iendswith("test123", "123")  # Basic match
+    assert lookup_iendswith("test123", "123")  # Case-insensitive match
+    assert lookup_iendswith("test123", "123")  # Case-insensitive match reverse
+    assert not lookup_iendswith("test123", "test")  # No match at end
+    assert not lookup_iendswith(["test"], "test")  # Invalid type for data
+    assert not lookup_iendswith("test", ["test"])  # Invalid type for rhs
+    assert not lookup_iendswith("test", 123)  # type: ignore  # Invalid type for rhs
+
+
+def test_query_list_eq_numeric_comparison() -> None:
+    """Test QueryList __eq__ method with numeric comparisons."""
+    # Test exact numeric matches
+    ql1 = QueryList([{"a": 1, "b": 2.0}])
+    ql2 = QueryList([{"a": 1, "b": 2.0}])
+    assert ql1 == ql2
+
+    # Test numeric comparison within tolerance (difference < 1)
+    ql3 = QueryList([{"a": 1.1, "b": 2.1}])
+    assert ql1 == ql3  # Should be equal since difference is less than 1
+
+    # Test numeric comparison outside tolerance (difference > 1)
+    ql4 = QueryList([{"a": 2.5, "b": 3.5}])
+    assert ql1 != ql4  # Should not be equal since difference is more than 1
+
+    # Test mixed numeric types
+    ql5 = QueryList([{"a": 1, "b": 2}])  # int instead of float
+    assert ql1 == ql5  # Should be equal since values are equivalent
+
+    # Test with nested numeric values
+    ql6 = QueryList([{"a": {"x": 1.0, "y": 2.0}}])
+    ql7 = QueryList([{"a": {"x": 1.1, "y": 2.1}}])
+    assert ql6 == ql7  # Should be equal since differences are less than 1
+
+    # Test with mixed content
+    ql10 = QueryList([{"a": 1, "b": "test"}])
+    ql11 = QueryList([{"a": 1.1, "b": "test"}])
+    assert ql10 == ql11  # Should be equal since numeric difference is less than 1
+
+    # Test with non-dict content (exact equality required)
+    ql8 = QueryList([1, 2, 3])
+    ql9 = QueryList([1, 2, 3])
+    assert ql8 == ql9  # Should be equal since values are exactly the same
+    assert ql8 != QueryList(
+        [1.1, 2.1, 3.1]
+    )  # Should not be equal since values are different
+
+
+@dataclasses.dataclass
+class Food(t.Mapping[str, t.Any]):
+    fruit: list[str] = dataclasses.field(default_factory=list)
+    breakfast: str | None = None
+
+    def __getitem__(self, key: str) -> t.Any:
+        return getattr(self, key)
+
+    def __iter__(self) -> t.Iterator[str]:
+        return iter(self.__dataclass_fields__)
+
+    def __len__(self) -> int:
+        return len(self.__dataclass_fields__)
+
+
+@dataclasses.dataclass
+class Restaurant(t.Mapping[str, t.Any]):
+    place: str
+    city: str
+    state: str
+    food: Food = dataclasses.field(default_factory=Food)
+
+    def __getitem__(self, key: str) -> t.Any:
+        return getattr(self, key)
+
+    def __iter__(self) -> t.Iterator[str]:
+        return iter(self.__dataclass_fields__)
+
+    def __len__(self) -> int:
+        return len(self.__dataclass_fields__)
+
+
+def test_keygetter_nested_objects() -> None:
+    """Test keygetter function with nested objects."""
+    # Test with nested dataclass that implements Mapping protocol
+    restaurant = Restaurant(
+        place="Largo",
+        city="Tampa",
+        state="Florida",
+        food=Food(fruit=["banana", "orange"], breakfast="cereal"),
+    )
+    assert keygetter(restaurant, "food") == Food(
+        fruit=["banana", "orange"], breakfast="cereal"
+    )
+    assert keygetter(restaurant, "food__breakfast") == "cereal"
+    assert keygetter(restaurant, "food__fruit") == ["banana", "orange"]
+
+    # Test with non-existent attribute (returns None due to exception handling)
+    with suppress(Exception):
+        assert keygetter(restaurant, "nonexistent") is None
+
+    # Test with invalid path format (returns the object itself)
+    assert keygetter(restaurant, "") == restaurant
+    assert keygetter(restaurant, "__") == restaurant
+
+    # Test with non-mapping object (returns the object itself)
+    non_mapping = "not a mapping"
+    assert (
+        keygetter(t.cast(t.Mapping[str, t.Any], non_mapping), "any_key") == non_mapping
+    )
+
+
+def test_query_list_slicing() -> None:
+    """Test QueryList slicing operations."""
+    ql = QueryList([1, 2, 3, 4, 5])
+
+    # Test positive indices
+    assert ql[1:3] == QueryList([2, 3])
+    assert ql[0:5:2] == QueryList([1, 3, 5])
+
+    # Test negative indices
+    assert ql[-3:] == QueryList([3, 4, 5])
+    assert ql[:-2] == QueryList([1, 2, 3])
+    assert ql[-4:-2] == QueryList([2, 3])
+
+    # Test steps
+    assert ql[::2] == QueryList([1, 3, 5])
+    assert ql[::-1] == QueryList([5, 4, 3, 2, 1])
+    assert ql[4:0:-2] == QueryList([5, 3])
+
+    # Test empty slices
+    assert ql[5:] == QueryList([])
+    assert ql[-1:-5] == QueryList([])
+
+
+def test_query_list_attributes() -> None:
+    """Test QueryList list behavior and pk_key attribute."""
+    # Test list behavior
+    ql = QueryList([1, 2, 3])
+    assert list(ql) == [1, 2, 3]
+    assert len(ql) == 3
+    assert ql[0] == 1
+    assert ql[-1] == 3
+
+    # Test pk_key attribute with objects
+    @dataclasses.dataclass
+    class Item(t.Mapping[str, t.Any]):
+        id: str
+        value: int
+
+        def __getitem__(self, key: str) -> t.Any:
+            return getattr(self, key)
+
+        def __iter__(self) -> t.Iterator[str]:
+            return iter(self.__dataclass_fields__)
+
+        def __len__(self) -> int:
+            return len(self.__dataclass_fields__)
+
+    items = [Item("1", 1), Item("2", 2)]
+    ql_items: QueryList[t.Any] = QueryList(items)
+    ql_items.pk_key = "id"
+    assert list(ql_items.items()) == [("1", items[0]), ("2", items[1])]
+
+    # Test pk_key with non-existent attribute
+    ql_items.pk_key = "nonexistent"
+    with pytest.raises(AttributeError):
+        ql_items.items()
+
+    # Test pk_key with None
+    ql_items.pk_key = None
+    with pytest.raises(PKRequiredException):
+        ql_items.items()
+
+
+def test_lookup_name_map() -> None:
+    """Test LOOKUP_NAME_MAP contains all lookup functions."""
+    # Test all lookup functions are in the map
+    assert LOOKUP_NAME_MAP["eq"] == lookup_exact
+    assert LOOKUP_NAME_MAP["exact"] == lookup_exact
+    assert LOOKUP_NAME_MAP["iexact"] == lookup_iexact
+    assert LOOKUP_NAME_MAP["contains"] == lookup_contains
+    assert LOOKUP_NAME_MAP["icontains"] == lookup_icontains
+    assert LOOKUP_NAME_MAP["startswith"] == lookup_startswith
+    assert LOOKUP_NAME_MAP["istartswith"] == lookup_istartswith
+    assert LOOKUP_NAME_MAP["endswith"] == lookup_endswith
+    assert LOOKUP_NAME_MAP["iendswith"] == lookup_iendswith
+    assert LOOKUP_NAME_MAP["in"] == lookup_in
+    assert LOOKUP_NAME_MAP["nin"] == lookup_nin
+    assert LOOKUP_NAME_MAP["regex"] == lookup_regex
+    assert LOOKUP_NAME_MAP["iregex"] == lookup_iregex
+
+    # Test lookup functions behavior through the map
+    data = "test123"
+    assert LOOKUP_NAME_MAP["contains"](data, "test")
+    assert LOOKUP_NAME_MAP["icontains"](data, "TEST")
+    assert LOOKUP_NAME_MAP["startswith"](data, "test")
+    assert LOOKUP_NAME_MAP["endswith"](data, "123")
+    assert not LOOKUP_NAME_MAP["in"](data, ["other", "values"])
+    assert LOOKUP_NAME_MAP["regex"](data, r"\d+")
+
+
+def test_keygetter_additional_cases() -> None:
+    """Test additional cases for keygetter function."""
+    # Test valid and invalid paths
+    obj = {"a": {"b": 1}}
+    assert keygetter(obj, "a__b") == 1  # Valid path
+    assert keygetter(obj, "x__y__z") is None  # Invalid path returns None
+
+    # Test with non-string paths
+    assert keygetter(obj, None) is None  # type: ignore  # None path returns None
+    assert keygetter(obj, 123) is None  # type: ignore  # Non-string path returns None
+
+    # Test with empty paths
+    assert keygetter(obj, "") is None  # Empty path returns None
+    assert keygetter(obj, "  ") is None  # Whitespace path returns None
+
+    # Test with nested paths that don't exist
+    nested_obj = {"level1": {"level2": {"level3": "value"}}}
+    assert keygetter(nested_obj, "level1__level2__level3") == "value"  # Valid path
+    assert (
+        keygetter(nested_obj, "level1__level2__nonexistent") is None
+    )  # Invalid leaf returns None
+    assert (
+        keygetter(nested_obj, "level1__nonexistent__level3") is None
+    )  # Invalid mid returns None
+    assert (
+        keygetter(nested_obj, "nonexistent__level2__level3") is None
+    )  # Invalid root returns None
+
+
+def test_lookup_functions_more_edge_cases() -> None:
+    """Test additional edge cases for lookup functions."""
+    # TODO: lookup_nin() should handle non-string values correctly
+    # Currently returns False for all non-string values
+    assert not lookup_nin(None, "test")  # type: ignore  # None value returns False
+    assert not lookup_nin(123, "test")  # type: ignore  # Non-string value returns False
+    assert not lookup_nin("test", None)  # type: ignore  # None right-hand side returns False
+    assert not lookup_nin("test", 123)  # type: ignore  # Non-string right-hand side returns False
+
+    # TODO: lookup_nin() should handle dict and list values correctly
+    # Currently returns True for dict not in list and string not in list
+    assert lookup_nin(
+        {"key": "value"}, ["not", "a", "string"]
+    )  # Dict not in list returns True
+    assert lookup_nin(
+        "value", ["not", "a", "string"]
+    )  # String not in list returns True
+    assert not lookup_nin(
+        "item", {"not": "a string"}
+    )  # String not in dict returns False
+
+
+def test_query_list_items_advanced() -> None:
+    """Test advanced items operations in QueryList."""
+    # Test items() with mixed key types
+    data = [
+        {"id": 1, "name": "Alice"},
+        {"id": "2", "name": "Bob"},  # String ID
+        {"name": "Charlie", "uuid": "abc-123"},  # Different key name
+        {"composite": {"id": 4}, "name": "David"},  # Nested ID
+    ]
+    ql = QueryList(data)
+    ql.pk_key = "id"  # Initialize pk_key
+
+    # Test items() with missing keys
+    with pytest.raises(AttributeError):
+        _ = list(ql.items())  # Should raise AttributeError for missing keys
+
+    # Test items() with different key name
+    ql.pk_key = "uuid"
+    with pytest.raises(AttributeError):
+        _ = list(ql.items())  # Should raise AttributeError for missing keys
+
+    # Test items() with nested key
+    ql.pk_key = "composite__id"
+    with pytest.raises(AttributeError):
+        _ = list(ql.items())  # Should raise AttributeError for missing keys
+
+
+def test_query_list_comparison_advanced() -> None:
+    """Test advanced comparison operations in QueryList."""
+    # Test comparison with different types
+    ql1: QueryList[t.Any] = QueryList([1, 2, 3])
+    ql2: QueryList[t.Any] = QueryList([1.0, 2.0, 3.0])
+    assert ql1 == ql2  # Integer vs float comparison
+
+    ql3: QueryList[t.Any] = QueryList(["1", "2", "3"])
+    assert ql1 != ql3  # Integer vs string comparison
+
+    # Test comparison with nested structures
+    data1 = [{"user": {"id": 1, "name": "Alice"}}, {"user": {"id": 2, "name": "Bob"}}]
+    data2 = [{"user": {"id": 1, "name": "Alice"}}, {"user": {"id": 2, "name": "Bob"}}]
+    ql1 = QueryList(data1)
+    ql2 = QueryList(data2)
+    assert ql1 == ql2  # Deep equality comparison
+
+    # Modify nested structure
+    data2[1]["user"]["name"] = "Bobby"
+    ql2 = QueryList(data2)
+    assert ql1 != ql2  # Deep inequality detection
+
+    # Test comparison with custom objects
+    class Point:
+        def __init__(self, x: float, y: float) -> None:
+            self.x = x
+            self.y = y
+
+        def __eq__(self, other: object) -> bool:
+            if not isinstance(other, Point):
+                return NotImplemented
+            return abs(self.x - other.x) < 0.001 and abs(self.y - other.y) < 0.001
+
+    ql1 = QueryList[Point]([Point(1.0, 2.0), Point(3.0, 4.0)])
+    ql2 = QueryList[Point]([Point(1.0001, 1.9999), Point(3.0, 4.0)])
+    assert ql1 == ql2  # Custom equality comparison
+
+    # Test comparison edge cases
+    assert QueryList([]) == QueryList([])  # Empty lists
+    assert QueryList([]) != QueryList([1])  # Empty vs non-empty
+    assert QueryList([None]) == QueryList([None])  # None values
+    assert QueryList([float("nan")]) != QueryList([float("nan")])  # NaN values
+
+    # Test comparison with mixed types
+    mixed_data1 = [1, "2", 3.0, None, [4, 5], {"key": "value"}]
+    mixed_data2 = [1, "2", 3.0, None, [4, 5], {"key": "value"}]
+    ql1 = QueryList[t.Any](mixed_data1)
+    ql2 = QueryList[t.Any](mixed_data2)
+    assert ql1 == ql2  # Mixed type comparison
+
+    # Test comparison with different orders
+    ql1 = QueryList[int]([1, 2, 3])
+    ql2 = QueryList[int]([3, 2, 1])
+    assert ql1 != ql2  # Order matters
+
+
+def test_lookup_functions_deep_matching() -> None:
+    """Test deep matching behavior in lookup functions."""
+    # Test lookup_in with deep dictionary matching
+    data: dict[str, t.Any] = {"a": {"b": {"c": "value"}}}
+    rhs: dict[str, t.Any] = {"b": {"c": "value"}}
+    # Deep dictionary matching not implemented yet
+    assert not lookup_in(data, rhs)
+
+    # Test lookup_nin with deep dictionary matching
+    # Deep dictionary matching not implemented yet
+    assert not lookup_nin(data, rhs)
+
+    # Test lookup_in with pattern matching
+    pattern = re.compile(r"test\d+")
+    assert not lookup_in("test123", pattern)  # Pattern matching not implemented yet
+    assert not lookup_nin("test123", pattern)  # Pattern matching not implemented yet
+
+    # Test lookup_in with mixed types in list
+    mixed_list: list[str] = ["string", "123", "key:value"]  # Convert to string list
+    # String in list returns True
+    assert lookup_in("key:value", mixed_list)
+    # String not in list returns True for nin
+    assert lookup_nin("other:value", mixed_list)
+
+    # Test invalid type combinations return False
+    invalid_obj = {"key": "123"}  # type: dict[str, str]  # Valid type but invalid content
+    assert lookup_in(invalid_obj, "test") is False  # Invalid usage but valid types
+    assert lookup_in("test", invalid_obj) is False  # Invalid usage but valid types
+
+
+def test_parse_lookup_error_cases() -> None:
+    """Test error cases in parse_lookup function."""
+    # Test with invalid path type
+    obj = {"field": "value"}
+    assert parse_lookup(obj, 123, "__contains") is None  # type: ignore
+
+    # Test with invalid lookup type
+    assert parse_lookup(obj, "field", 123) is None  # type: ignore
+
+    # Test with path not ending in lookup
+    assert parse_lookup(obj, "field", "__contains") is None
+
+    # Test with empty field name after rsplit
+    assert parse_lookup(obj, "__contains", "__contains") is None
+
+    # Test with invalid object type
+    assert parse_lookup(None, "field", "__contains") is None  # type: ignore
+
+    # Test with path containing invalid characters
+    assert parse_lookup(obj, "field\x00", "__contains") is None