diff --git a/README.md b/README.md
index 4351171..3d838ec 100644
--- a/README.md
+++ b/README.md
@@ -197,7 +197,7 @@ header = klamath.library.FileHeader.read(stream)
 struct_positions = klamath.library.scan_structs(stream)
 
 stream.seek(struct_positions[b'my_struct'])
-elements_A = klamath.library.read_elements(stream)
+elements_A = klamath.library.try_read_struct(stream)
 
 stream.close()
 
diff --git a/klamath/__init__.py b/klamath/__init__.py
index 5a315b4..8de1f87 100644
--- a/klamath/__init__.py
+++ b/klamath/__init__.py
@@ -36,5 +36,5 @@ from . import (
     )
 
 __author__ = 'Jan Petykiewicz'
-__version__ = '1.5'
+__version__ = '1.4'
 
diff --git a/klamath/basic.py b/klamath/basic.py
index e880393..86c9d59 100644
--- a/klamath/basic.py
+++ b/klamath/basic.py
@@ -49,7 +49,7 @@ def decode_real8(nums: NDArray[numpy.uint64]) -> NDArray[numpy.float64]:
     exp = (nums >> 56) & 0x7f
     mant = (nums & 0x00ff_ffff_ffff_ffff).astype(numpy.float64)
     mant[neg != 0] *= -1
-    return numpy.ldexp(mant, 4 * (exp.astype(numpy.int64) - 64) - 56)
+    return numpy.ldexp(mant, 4 * (exp - 64) - 56, signature=(float, int, float))
 
 
 def parse_real8(data: bytes) -> NDArray[numpy.float64]:
@@ -77,7 +77,7 @@ def parse_datetime(data: bytes) -> list[datetime]:
         year, *date_parts = parse_int2(data[ii:ii + 12])
         try:
             dt = datetime(year + 1900, *date_parts)
-        except ValueError:
+        except ValueError as err:
             dt = datetime(1900, 1, 1, 0, 0, 0)
             logger.info(f'Invalid date {[year] + date_parts}, setting {dt} instead')
         dts.append(dt)
@@ -149,7 +149,7 @@ def encode_real8(fnums: NDArray[numpy.float64]) -> NDArray[numpy.uint64]:
     gds_exp = exp16 + 64
 
     neg_biased = (gds_exp < 0)
-    gds_mant[neg_biased] >>= (-gds_exp[neg_biased] * 4).astype(numpy.uint16)
+    gds_mant[neg_biased] >>= (gds_exp[neg_biased] * 4).astype(numpy.uint16)
     gds_exp[neg_biased] = 0
 
     too_big = (gds_exp > 0x7f) & ~(zero | subnorm)
@@ -160,6 +160,7 @@ def encode_real8(fnums: NDArray[numpy.float64]) -> NDArray[numpy.uint64]:
 
     real8 = sign | gds_exp_bits | gds_mant
     real8[zero] = 0
+    real8[gds_exp < -14] = 0  # number is too small
 
     return real8.astype(numpy.uint64, copy=False)
 
diff --git a/klamath/elements.py b/klamath/elements.py
index c0d5567..302921c 100644
--- a/klamath/elements.py
+++ b/klamath/elements.py
@@ -2,9 +2,7 @@
 Functionality for reading/writing elements (geometry, text labels,
  structure references) and associated properties.
 """
-import io
 from typing import IO, TypeVar
-from collections.abc import Mapping
 from abc import ABCMeta, abstractmethod
 from dataclasses import dataclass
 
@@ -54,13 +52,11 @@ def read_properties(stream: IO[bytes]) -> dict[int, bytes]:
             if key in properties:
                 raise KlamathError(f'Duplicate property key: {key!r}')
             properties[key] = value
-        else:
-            stream.seek(size, io.SEEK_CUR)
         size, tag = Record.read_header(stream)
     return properties
 
 
-def write_properties(stream: IO[bytes], properties: Mapping[int, bytes]) -> int:
+def write_properties(stream: IO[bytes], properties: dict[int, bytes]) -> int:
     """
     Write element properties.
 
@@ -151,7 +147,7 @@ class Reference(Element):
     colrow: tuple[int, int] | NDArray[numpy.int16] | None
     """ Number of columns and rows (AREF) or None (SREF) """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties associated with this reference. """
 
     @classmethod
@@ -233,7 +229,7 @@ class Boundary(Element):
     xy: NDArray[numpy.int32]
     """ Ordered vertices of the shape. First and last points should be identical. """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties for the element. """
 
     @classmethod
@@ -279,7 +275,7 @@ class Path(Element):
     xy: NDArray[numpy.int32]
     """ Path centerline coordinates """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties for the element. """
 
     @classmethod
@@ -319,12 +315,12 @@ class Path(Element):
         if self.width != 0:
             b += WIDTH.write(stream, self.width)
 
-        if self.path_type == 4:
+        if self.path_type < 4:
             bgn_ext, end_ext = self.extension
             if bgn_ext != 0:
-                b += BGNEXTN.write(stream, int(bgn_ext))
+                b += BGNEXTN.write(stream, bgn_ext)
             if end_ext != 0:
-                b += ENDEXTN.write(stream, int(end_ext))
+                b += ENDEXTN.write(stream, end_ext)
         b += XY.write(stream, self.xy)
         b += write_properties(stream, self.properties)
         b += ENDEL.write(stream, None)
@@ -344,7 +340,7 @@ class Box(Element):
     xy: NDArray[numpy.int32]
     """ Box coordinates (5 pairs) """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties for the element. """
 
     @classmethod
@@ -378,7 +374,7 @@ class Node(Element):
     xy: NDArray[numpy.int32]
     """ 1-50 pairs of coordinates. """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties for the element. """
 
     @classmethod
@@ -438,7 +434,7 @@ class Text(Element):
     string: bytes
     """ Text content """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties for the element. """
 
     @classmethod
diff --git a/klamath/library.py b/klamath/library.py
index 8b3ab20..f7b68bd 100644
--- a/klamath/library.py
+++ b/klamath/library.py
@@ -220,15 +220,10 @@ def scan_hierarchy(stream: IO[bytes]) -> dict[bytes, dict[bytes, int]]:
             colrow = COLROW.read_data(stream, size)
             ref_count = colrow[0] * colrow[1]
         elif tag == ENDEL.tag:
-            if ref_name is not None:
-                if ref_count is None:
-                    ref_count = 1
-                cur_structure[ref_name] += ref_count
-            ref_name = None
-            ref_count = None
-        elif tag in (SREF.tag, AREF.tag):
-            ref_name = None
-            ref_count = None
+            if ref_count is None:
+                ref_count = 1
+            assert ref_name is not None
+            cur_structure[ref_name] += ref_count
         else:
             stream.seek(size, io.SEEK_CUR)
         size, tag = Record.read_header(stream)
diff --git a/klamath/record.py b/klamath/record.py
index f5fce86..48bfe7c 100644
--- a/klamath/record.py
+++ b/klamath/record.py
@@ -142,7 +142,7 @@ class NoDataRecord(Record[None, None]):
     @classmethod
     def pack_data(cls: type[Self], data: None) -> bytes:
         if data is not None:
-            raise KlamathError('?? Packing {data!r} into NoDataRecord??')
+            raise KlamathError('?? Packing {data} into NoDataRecord??')
         return b''
 
 
diff --git a/klamath/records.py b/klamath/records.py
index b05bb04..0fbcb4d 100644
--- a/klamath/records.py
+++ b/klamath/records.py
@@ -18,7 +18,7 @@ class HEADER(Int2Record):
 
 class BGNLIB(DateTimeRecord):
     tag = 0x0102
-    expected_size = 2 * 6 * 2
+    expected_size = 6 * 2
 
 
 class LIBNAME(ASCIIRecord):
@@ -37,7 +37,7 @@ class ENDLIB(NoDataRecord):
 
 class BGNSTR(DateTimeRecord):
     tag = 0x0502
-    expected_size = 2 * 6 * 2
+    expected_size = 6 * 2
 
 
 class STRNAME(ASCIIRecord):
@@ -173,8 +173,6 @@ class GENERATIONS(Int2Record):
 
     @classmethod
     def check_data(cls: type[Self], data: NDArray[numpy.integer] | Sequence[int] | int) -> None:
-        if isinstance(data, (int, numpy.integer)):
-            return
         if not isinstance(data, Sized) or len(data) != 1:
             raise KlamathError(f'Expected exactly one integer, got {data}')
 
@@ -224,6 +222,7 @@ class PROPATTR(Int2Record):
 
 class PROPVALUE(ASCIIRecord):
     tag = 0x2c06
+    expected_size = 2
 
 
 class BOX(NoDataRecord):
@@ -272,8 +271,6 @@ class FORMAT(Int2Record):
 
     @classmethod
     def check_data(cls: type[Self], data: NDArray[numpy.integer] | Sequence[int] | int) -> None:
-        if isinstance(data, (int, numpy.integer)):
-            return
         if not isinstance(data, Sized) or len(data) != 1:
             raise KlamathError(f'Expected exactly one integer, got {data}')
 
@@ -309,7 +306,7 @@ class SOFTFENCE(NoDataRecord):
 
 
 class HARDFENCE(NoDataRecord):
-    tag = 0x3e00
+    tag = 0x3f00
 
 
 class SOFTWIRE(NoDataRecord):
diff --git a/klamath/test_basic.py b/klamath/test_basic.py
index 287f7a9..4d686d9 100644
--- a/klamath/test_basic.py
+++ b/klamath/test_basic.py
@@ -120,7 +120,7 @@ def test_pack_ascii() -> None:
     assert pack_ascii(b'321') == b'321\0'
 
 
-def test_invalid_date() -> None:
+def test_invalid_date():
     default = [datetime(1900, 1, 1, 0, 0, 0)]
     assert parse_datetime(pack_int2((0, 0, 0, 0, 0, 0))) == default
     assert parse_datetime(pack_int2((0, 1, 32, 0, 0, 0))) == default
diff --git a/klamath/test_elements.py b/klamath/test_elements.py
deleted file mode 100644
index ae3df18..0000000
--- a/klamath/test_elements.py
+++ /dev/null
@@ -1,156 +0,0 @@
-import io
-import numpy
-from numpy.testing import assert_array_equal
-from klamath.elements import Boundary, Path, Text, Reference, Box, Node
-
-def test_boundary_roundtrip() -> None:
-    xy = numpy.array([[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], dtype=numpy.int32)
-    b = Boundary(layer=(4, 5), xy=xy, properties={1: b'prop1'})
-
-    stream = io.BytesIO()
-    b.write(stream)
-    stream.seek(0)
-
-    b2 = Boundary.read(stream)
-    assert b2.layer == b.layer
-    assert_array_equal(b2.xy, b.xy)
-    assert b2.properties == b.properties
-
-def test_path_roundtrip() -> None:
-    xy = numpy.array([[0, 0], [100, 0], [100, 100]], dtype=numpy.int32)
-    p = Path(layer=(10, 20), xy=xy, properties={2: b'pathprop'},
-             path_type=4, width=50, extension=(10, 20))
-
-    stream = io.BytesIO()
-    p.write(stream)
-    stream.seek(0)
-
-    p2 = Path.read(stream)
-    assert p2.layer == p.layer
-    assert_array_equal(p2.xy, p.xy)
-    assert p2.properties == p.properties
-    assert p2.path_type == p.path_type
-    assert p2.width == p.width
-    assert p2.extension == p.extension
-
-def test_text_roundtrip() -> None:
-    xy = numpy.array([[50, 50]], dtype=numpy.int32)
-    t = Text(layer=(1, 1), xy=xy, string=b"HELLO WORLD", properties={},
-             presentation=5, path_type=0, width=0, invert_y=True,
-             mag=2.5, angle_deg=45.0)
-
-    stream = io.BytesIO()
-    t.write(stream)
-    stream.seek(0)
-
-    t2 = Text.read(stream)
-    assert t2.layer == t.layer
-    assert_array_equal(t2.xy, t.xy)
-    assert t2.string == t.string
-    assert t2.presentation == t.presentation
-    assert t2.invert_y == t.invert_y
-    assert t2.mag == t.mag
-    assert t2.angle_deg == t.angle_deg
-
-def test_reference_sref_roundtrip() -> None:
-    xy = numpy.array([[100, 200]], dtype=numpy.int32)
-    r = Reference(struct_name=b"MY_CELL", xy=xy, colrow=None,
-                  properties={5: b'sref'}, invert_y=False, mag=1.0, angle_deg=90.0)
-
-    stream = io.BytesIO()
-    r.write(stream)
-    stream.seek(0)
-
-    r2 = Reference.read(stream)
-    assert r2.struct_name == r.struct_name
-    assert_array_equal(r2.xy, r.xy)
-    assert r2.colrow is None
-    assert r2.properties == r.properties
-    assert r2.angle_deg == r.angle_deg
-
-def test_reference_aref_roundtrip() -> None:
-    xy = numpy.array([[0, 0], [1000, 0], [0, 500]], dtype=numpy.int32)
-    colrow = (5, 2)
-    r = Reference(struct_name=b"ARRAY_CELL", xy=xy, colrow=colrow,
-                  properties={}, invert_y=False, mag=1.0, angle_deg=0.0)
-
-    stream = io.BytesIO()
-    r.write(stream)
-    stream.seek(0)
-
-    r2 = Reference.read(stream)
-    assert r2.struct_name == r.struct_name
-    assert_array_equal(r2.xy, r.xy)
-    assert r2.colrow is not None
-    assert list(r2.colrow) == list(colrow)
-    assert r2.properties == r.properties
-
-def test_box_roundtrip() -> None:
-    xy = numpy.array([[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], dtype=numpy.int32)
-    b = Box(layer=(30, 40), xy=xy, properties={})
-
-    stream = io.BytesIO()
-    b.write(stream)
-    stream.seek(0)
-
-    b2 = Box.read(stream)
-    assert b2.layer == b.layer
-    assert_array_equal(b2.xy, b.xy)
-
-def test_node_roundtrip() -> None:
-    xy = numpy.array([[0, 0], [10, 10]], dtype=numpy.int32)
-    n = Node(layer=(50, 60), xy=xy, properties={})
-
-    stream = io.BytesIO()
-    n.write(stream)
-    stream.seek(0)
-
-    n2 = Node.read(stream)
-    assert n2.layer == n.layer
-    assert_array_equal(n2.xy, n.xy)
-
-def test_reference_check() -> None:
-    import pytest
-    from klamath.basic import KlamathError
-    # SREF with too many points
-    xy = numpy.array([[0, 0], [10, 10]], dtype=numpy.int32)
-    r = Reference(struct_name=b"CELL", xy=xy, colrow=None, properties={}, invert_y=False, mag=1.0, angle_deg=0.0)
-    with pytest.raises(KlamathError, match="Expected size-2 xy"):
-        r.check()
-
-    # AREF with too few points
-    xy = numpy.array([[0, 0]], dtype=numpy.int32)
-    r = Reference(struct_name=b"CELL", xy=xy, colrow=(2, 2), properties={}, invert_y=False, mag=1.0, angle_deg=0.0)
-    with pytest.raises(KlamathError, match="colrow is not None, so expected size-6 xy"):
-        r.check()
-
-def test_read_properties_duplicate() -> None:
-    import pytest
-    from klamath.basic import KlamathError
-    from klamath.records import PROPATTR, PROPVALUE, ENDEL
-    stream = io.BytesIO()
-    PROPATTR.write(stream, 1)
-    PROPVALUE.write(stream, b"val1")
-    PROPATTR.write(stream, 1) # DUPLICATE
-    PROPVALUE.write(stream, b"val2")
-    ENDEL.write(stream, None)
-    stream.seek(0)
-
-    from klamath.elements import read_properties
-    with pytest.raises(KlamathError, match="Duplicate property key"):
-        read_properties(stream)
-
-def test_element_read_unexpected_tag() -> None:
-    import pytest
-    from klamath.basic import KlamathError
-    from klamath.records import SREF, SNAME, HEADER, XY, ENDEL
-    stream = io.BytesIO()
-    SREF.write(stream, None)
-    SNAME.write(stream, b"CELL")
-    HEADER.write(stream, 123) # UNEXPECTED TAG for Reference.read
-    XY.write(stream, [0, 0])
-    ENDEL.write(stream, None)
-    stream.seek(0)
-
-    with pytest.raises(KlamathError, match="Unexpected tag"):
-        Reference.read(stream)
diff --git a/klamath/test_library.py b/klamath/test_library.py
deleted file mode 100644
index a27c65c..0000000
--- a/klamath/test_library.py
+++ /dev/null
@@ -1,102 +0,0 @@
-import io
-import numpy
-from datetime import datetime
-from klamath.library import FileHeader, write_struct, try_read_struct, scan_structs, scan_hierarchy, read_elements
-from klamath.elements import Boundary
-from klamath.records import ENDLIB
-
-def test_file_header_roundtrip() -> None:
-    h = FileHeader(name=b"MY_LIB", user_units_per_db_unit=0.001, meters_per_db_unit=1e-9,
-                   mod_time=datetime(2023, 1, 1, 0, 0, 0), acc_time=datetime(2023, 1, 1, 0, 0, 0))
-
-    stream = io.BytesIO()
-    h.write(stream)
-    stream.seek(0)
-
-    h2 = FileHeader.read(stream)
-    assert h2.name == h.name
-    assert h2.user_units_per_db_unit == h.user_units_per_db_unit
-    assert h2.meters_per_db_unit == h.meters_per_db_unit
-    assert h2.mod_time == h.mod_time
-
-def test_write_read_struct() -> None:
-    xy = numpy.array([[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], dtype=numpy.int32)
-    b = Boundary(layer=(1, 1), xy=xy, properties={})
-
-    stream = io.BytesIO()
-    # Need a header for some operations, but write_struct works standalone
-    write_struct(stream, name=b"CELL_A", elements=[b])
-    ENDLIB.write(stream, None)
-    stream.seek(0)
-
-    res = try_read_struct(stream)
-    assert res is not None
-    name, elements = res
-    assert name == b"CELL_A"
-    assert len(elements) == 1
-    assert isinstance(elements[0], Boundary)
-
-def test_scan_structs() -> None:
-    stream = io.BytesIO()
-    write_struct(stream, name=b"CELL_A", elements=[])
-    write_struct(stream, name=b"CELL_B", elements=[])
-    ENDLIB.write(stream, None)
-    stream.seek(0)
-
-    positions = scan_structs(stream)
-    assert b"CELL_A" in positions
-    assert b"CELL_B" in positions
-
-    # Verify we can seek and read
-    stream.seek(positions[b"CELL_B"])
-    elements = read_elements(stream)
-    assert len(elements) == 0
-
-def test_scan_hierarchy() -> None:
-    from klamath.elements import Reference
-
-    stream = io.BytesIO()
-    # Struct A has 2 refs to Struct B
-    ref_b1 = Reference(struct_name=b"B", xy=numpy.array([[0, 0]], dtype=numpy.int32), colrow=None, properties={},
-                       invert_y=False, mag=1.0, angle_deg=0.0)
-    ref_b2 = Reference(struct_name=b"B", xy=numpy.array([[10, 10]], dtype=numpy.int32), colrow=None, properties={},
-                       invert_y=False, mag=1.0, angle_deg=0.0)
-    write_struct(stream, name=b"A", elements=[ref_b1, ref_b2])
-
-    # Struct B has a 3x2 AREF of Struct C
-    ref_c = Reference(struct_name=b"C", xy=numpy.array([[0, 0], [10, 0], [0, 10]], dtype=numpy.int32),
-                      colrow=(3, 2), properties={}, invert_y=False, mag=1.0, angle_deg=0.0)
-    write_struct(stream, name=b"B", elements=[ref_c])
-
-    write_struct(stream, name=b"C", elements=[])
-    ENDLIB.write(stream, None)
-    stream.seek(0)
-
-    hierarchy = scan_hierarchy(stream)
-    assert hierarchy[b"A"] == {b"B": 2}
-    assert hierarchy[b"B"] == {b"C": 6}
-    assert hierarchy[b"C"] == {}
-
-def test_scan_structs_duplicate() -> None:
-    import pytest
-    from klamath.basic import KlamathError
-    stream = io.BytesIO()
-    write_struct(stream, name=b"CELL_A", elements=[])
-    write_struct(stream, name=b"CELL_A", elements=[])
-    ENDLIB.write(stream, None)
-    stream.seek(0)
-
-    with pytest.raises(KlamathError, match="Duplicate structure name"):
-        scan_structs(stream)
-
-def test_scan_hierarchy_duplicate() -> None:
-    import pytest
-    from klamath.basic import KlamathError
-    stream = io.BytesIO()
-    write_struct(stream, name=b"CELL_A", elements=[])
-    write_struct(stream, name=b"CELL_A", elements=[])
-    ENDLIB.write(stream, None)
-    stream.seek(0)
-
-    with pytest.raises(KlamathError, match="Duplicate structure name"):
-        scan_hierarchy(stream)
diff --git a/klamath/test_record.py b/klamath/test_record.py
deleted file mode 100644
index 99a5a1f..0000000
--- a/klamath/test_record.py
+++ /dev/null
@@ -1,134 +0,0 @@
-import io
-import pytest
-import struct
-from datetime import datetime
-from klamath.basic import KlamathError
-from klamath.record import (
-    write_record_header, read_record_header, expect_record,
-    BitArrayRecord, Int2Record, ASCIIRecord, DateTimeRecord, NoDataRecord
-)
-from klamath.records import ENDLIB, HEADER
-
-def test_write_read_record_header() -> None:
-    stream = io.BytesIO()
-    tag = 0x1234
-    data_size = 8
-
-    write_record_header(stream, data_size, tag)
-    stream.seek(0)
-
-    read_size, read_tag = read_record_header(stream)
-    assert read_size == data_size
-    assert read_tag == tag
-    assert stream.tell() == 4
-
-def test_write_record_header_too_big() -> None:
-    stream = io.BytesIO()
-    with pytest.raises(KlamathError, match="Record size is too big"):
-        write_record_header(stream, 0x10000, 0x1234)
-
-def test_read_record_header_errors() -> None:
-    # Too small
-    stream = io.BytesIO(struct.pack('>HH', 2, 0x1234))
-    with pytest.raises(KlamathError, match="Record size is too small"):
-        read_record_header(stream)
-
-    # Odd size
-    stream = io.BytesIO(struct.pack('>HH', 5, 0x1234))
-    with pytest.raises(KlamathError, match="Record size is odd"):
-        read_record_header(stream)
-
-def test_expect_record() -> None:
-    stream = io.BytesIO()
-    write_record_header(stream, 4, 0x1111)
-    stream.seek(0)
-
-    # Correct tag
-    size = expect_record(stream, 0x1111)
-    assert size == 4
-
-    # Incorrect tag
-    stream.seek(0)
-    with pytest.raises(KlamathError, match="Unexpected record"):
-        expect_record(stream, 0x2222)
-
-def test_bitarray_record() -> None:
-    class TestBit(BitArrayRecord):
-        tag = 0x9999
-
-    stream = io.BytesIO()
-    TestBit.write(stream, 0x8000)
-    stream.seek(0)
-
-    val = TestBit.read(stream)
-    assert val == 0x8000
-
-def test_int2_record() -> None:
-    class TestInt2(Int2Record):
-        tag = 0x8888
-
-    stream = io.BytesIO()
-    TestInt2.write(stream, [1, -2, 3])
-    stream.seek(0)
-
-    val = TestInt2.read(stream)
-    assert list(val) == [1, -2, 3]
-
-def test_ascii_record() -> None:
-    class TestASCII(ASCIIRecord):
-        tag = 0x7777
-
-    stream = io.BytesIO()
-    TestASCII.write(stream, b"HELLO")
-    stream.seek(0)
-
-    val = TestASCII.read(stream)
-    assert val == b"HELLO"
-
-def test_datetime_record() -> None:
-    class TestDT(DateTimeRecord):
-        tag = 0x6666
-
-    now = datetime(2023, 10, 27, 12, 30, 45)
-    stream = io.BytesIO()
-    TestDT.write(stream, [now, now])
-    stream.seek(0)
-
-    vals = TestDT.read(stream)
-    assert vals == [now, now]
-
-def test_nodata_record() -> None:
-    class TestNoData(NoDataRecord):
-        tag = 0x5555
-
-    stream = io.BytesIO()
-    TestNoData.write(stream, None)
-    stream.seek(0)
-
-    # Verify header: 4 bytes total (size=4, tag=0x5555), data_size=0
-    header = stream.read(4)
-    assert header == struct.pack('>HH', 4, 0x5555)
-
-    stream.seek(0)
-    assert TestNoData.read(stream) is None
-
-def test_record_skip_past() -> None:
-    stream = io.BytesIO()
-    HEADER.write(stream, 600)
-    ENDLIB.write(stream, None)
-
-    stream.seek(0)
-    # Skip past HEADER
-    found = HEADER.skip_past(stream)
-    assert found is True
-    assert stream.tell() == 6 # 4 header + 2 data
-
-    # Try to skip past something that doesn't exist before ENDLIB
-    class NONEXISTENT(NoDataRecord):
-        tag = 0xFFFF
-
-    stream.seek(0)
-    found = NONEXISTENT.skip_past(stream)
-    assert found is False
-    # Should be at the end of ENDLIB record header/tag read
-    assert stream.tell() == 10 # 6 (HEADER) + 4 (ENDLIB)
diff --git a/klamath/test_records.py b/klamath/test_records.py
deleted file mode 100644
index fd07b44..0000000
--- a/klamath/test_records.py
+++ /dev/null
@@ -1,110 +0,0 @@
-import io
-import pytest
-import numpy
-from datetime import datetime
-from klamath.basic import KlamathError
-from klamath import records
-
-def test_record_tags() -> None:
-    assert records.HEADER.tag == 0x0002
-    assert records.BGNLIB.tag == 0x0102
-    assert records.LIBNAME.tag == 0x0206
-    assert records.UNITS.tag == 0x0305
-    assert records.ENDLIB.tag == 0x0400
-    assert records.BGNSTR.tag == 0x0502
-    assert records.STRNAME.tag == 0x0606
-    assert records.ENDSTR.tag == 0x0700
-    assert records.BOUNDARY.tag == 0x0800
-    assert records.PATH.tag == 0x0900
-    assert records.SREF.tag == 0x0a00
-    assert records.AREF.tag == 0x0b00
-    assert records.TEXT.tag == 0x0c00
-    assert records.LAYER.tag == 0x0d02
-    assert records.DATATYPE.tag == 0x0e02
-    assert records.WIDTH.tag == 0x0f03
-    assert records.XY.tag == 0x1003
-    assert records.ENDEL.tag == 0x1100
-    assert records.SNAME.tag == 0x1206
-    assert records.COLROW.tag == 0x1302
-    assert records.NODE.tag == 0x1500
-    assert records.TEXTTYPE.tag == 0x1602
-    assert records.PRESENTATION.tag == 0x1701
-    assert records.STRING.tag == 0x1906
-    assert records.STRANS.tag == 0x1a01
-    assert records.MAG.tag == 0x1b05
-    assert records.ANGLE.tag == 0x1c05
-    assert records.REFLIBS.tag == 0x1f06
-    assert records.FONTS.tag == 0x2006
-    assert records.PATHTYPE.tag == 0x2102
-    assert records.GENERATIONS.tag == 0x2202
-    assert records.ATTRTABLE.tag == 0x2306
-    assert records.ELFLAGS.tag == 0x2601
-    assert records.NODETYPE.tag == 0x2a02
-    assert records.PROPATTR.tag == 0x2b02
-    assert records.PROPVALUE.tag == 0x2c06
-    assert records.BOX.tag == 0x2d00
-    assert records.BOXTYPE.tag == 0x2e02
-    assert records.PLEX.tag == 0x2f03
-    assert records.BGNEXTN.tag == 0x3003
-    assert records.ENDEXTN.tag == 0x3103
-    assert records.TAPENUM.tag == 0x3202
-    assert records.TAPECODE.tag == 0x3302
-    assert records.FORMAT.tag == 0x3602
-    assert records.MASK.tag == 0x3706
-    assert records.ENDMASKS.tag == 0x3800
-    assert records.LIBDIRSIZE.tag == 0x3902
-    assert records.SRFNAME.tag == 0x3a06
-    assert records.LIBSECUR.tag == 0x3b02
-
-def test_header_validation() -> None:
-    # Correct size
-    records.HEADER.check_size(2)
-
-    # Incorrect size
-    with pytest.raises(KlamathError, match="Expected size 2, got 4"):
-        records.HEADER.check_size(4)
-
-def test_bgnlib_validation() -> None:
-    now = datetime(2023, 10, 27, 12, 30, 45)
-    # Correct size (2 datetimes = 24 bytes)
-    records.BGNLIB.check_size(24)
-
-    # Incorrect size
-    with pytest.raises(KlamathError, match="Expected size 24, got 12"):
-        records.BGNLIB.check_size(12)
-
-def test_reflibs_fonts_validation() -> None:
-    # REFLIBS must be multiple of 44
-    records.REFLIBS.check_size(44)
-    records.REFLIBS.check_size(88)
-    records.REFLIBS.check_size(0)
-
-    with pytest.raises(KlamathError, match="Expected size to be multiple of 44"):
-        records.REFLIBS.check_size(10)
-
-def test_generations_format_validation() -> None:
-    # GENERATIONS expects exactly one integer
-    records.GENERATIONS.check_data(3)
-    records.GENERATIONS.check_data([1])
-
-    with pytest.raises(KlamathError, match="Expected exactly one integer"):
-        records.GENERATIONS.check_data([1, 2])
-
-def test_attrtable_validation() -> None:
-    # ATTRTABLE size <= 44
-    records.ATTRTABLE.check_size(44)
-    records.ATTRTABLE.check_size(10)
-
-    with pytest.raises(KlamathError, match="Expected size <= 44"):
-        records.ATTRTABLE.check_size(45)
-
-def test_nodata_records() -> None:
-    stream = io.BytesIO()
-    records.ENDLIB.write(stream, None)
-    stream.seek(0)
-    assert records.ENDLIB.read(stream) is None
-
-    stream = io.BytesIO()
-    records.BOUNDARY.write(stream, None)
-    stream.seek(0)
-    assert records.BOUNDARY.read(stream) is None
diff --git a/pyproject.toml b/pyproject.toml
index 5ca097d..c7d7a0e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,3 +1,7 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
 [project]
 name = "klamath"
 description = "GDSII format reader/writer"
@@ -40,7 +44,6 @@ classifiers = [
     "Intended Audience :: Science/Research",
     "License :: OSI Approved :: GNU General Public License v3 (GPLv3)",
     "Topic :: Scientific/Engineering :: Electronic Design Automation (EDA)",
-    "Topic :: File Formats",
     ]
 requires-python = ">=3.11"
 include = [
@@ -51,11 +54,6 @@ dependencies = [
     "numpy>=1.26",
     ]
 
-[build-system]
-requires = ["hatchling"]
-build-backend = "hatchling.build"
-
-
 [tool.hatch.version]
 path = "klamath/__init__.py"
 
@@ -80,6 +78,7 @@ lint.ignore = [
     "ANN002",   # *args
     "ANN003",   # **kwargs
     "ANN401",   # Any
+    "ANN101",   # self: Self
     "SIM108",   # single-line if / else assignment
     "RET504",   # x=y+z; return x
     "PIE790",   # unnecessary pass