diff --git a/tests/test_packer.py b/tests/test_packer.py
index ab69583..ce6db6c 100644
--- a/tests/test_packer.py
+++ b/tests/test_packer.py
@@ -208,8 +208,8 @@ def test_cross_library_transitive_dep(self, tmp_path):
               "module scaled_box(s) { cube(scale_val(s)); }")
         entry = write(tmp_path, "entry.scad",
                       "use <shapes.scad>\nscaled_box(5);")
-        # Note: use <math.scad> inside shapes.scad is processed with process_includes=True,
-        # so scale_val ends up in the pool via shapes.scad's flattened parse
+        # shapes.scad itself references math.scad, and packing resolves that dependency
+        # when processing the library, so scaled_box can be emitted correctly.
         result = pack(entry)
         assert "scaled_box" in result
 
@@ -373,7 +373,7 @@ def test_escaped_quote_inside_string_preserved(self):
 
     def test_unterminated_string_at_eof_handled(self):
         # A string literal that reaches EOF without a closing `"` must not crash —
-        # exercises the `while i < len(code)` exit-without-break branch (58->68).
+        # exercises the string-scanning loop path where EOF is reached before a closing quote.
         result = _strip_expression_comments('"unclosed')
         assert '"unclosed' in result
 
@@ -459,8 +459,8 @@ def test_fallback_warning_when_string_parse_fails(self, tmp_path, capsys, monkey
         assert "warning" in captured.err.lower()
 
     def test_fallback_no_warning_for_empty_file(self, tmp_path, capsys, monkeypatch):
-        # When getASTfromString fails AND the file is empty, the fallback also returns
-        # nothing — `if nodes:` is False so no warning is printed (branch 239->245).
+        # When getASTfromString fails and the file is empty, the fallback returns
+        # no nodes, so `if nodes:` is False and no warning is printed.
         entry = write(tmp_path, "entry.scad", "")
         monkeypatch.setattr("openscad_packer.packer.getASTfromString", lambda *a, **kw: None)
         result = Packer(str(entry), []).pack()
diff --git a/tests/test_resolver.py b/tests/test_resolver.py
index 4de9f29..0031b4d 100644
--- a/tests/test_resolver.py
+++ b/tests/test_resolver.py
@@ -1,8 +1,6 @@
 """Unit tests for openscad_packer.resolver."""
 from pathlib import Path
 
-import pytest
-
 from openscad_packer.resolver import resolve_library
 
 
diff --git a/tests/test_shaker.py b/tests/test_shaker.py
index 1c0a0c8..9a5e5a9 100644
--- a/tests/test_shaker.py
+++ b/tests/test_shaker.py
@@ -1,7 +1,6 @@
 """Unit tests for openscad_packer.shaker."""
 from pathlib import Path
 
-import pytest
 from openscad_parser.ast import getASTfromFile
 from openscad_parser.ast.nodes import FunctionDeclaration, ModuleDeclaration
 
@@ -24,7 +23,7 @@ def make_pool(tmp_path: Path, content: str) -> dict:
             if name not in pool:
                 pool[name] = []
             for i, existing in enumerate(pool[name]):
-                if type(existing) is type(node):
+                if isinstance(existing, type(node)):
                     pool[name][i] = node
                     break
             else:
diff --git a/tests/test_upstream_patches.py b/tests/test_upstream_patches.py
index 518b351..0d8ea57 100644
--- a/tests/test_upstream_patches.py
+++ b/tests/test_upstream_patches.py
@@ -127,14 +127,15 @@ def test_three_arg_range_explicit_step_preserved(self, tmp_path):
         assert "[0:1:2]" in out
 
     def test_three_arg_range_large_step_preserved(self, tmp_path):
-        # [0:5:1] means start=0, step=5, end=1 — semantically different from [0:5]
+        # [0:5:1] means start=0, step=5, end=1 — semantically different from [0:1]
+        # ([0:5] is a two-arg range: start=0, end=5, implicit step=1.)
         src = "x = [for (i=[0:5:1]) i];"
         out = parse_and_print(tmp_path / "t.scad", src)
         assert "[0:5:1]" in out
         assert "[0:5]" not in out
 
     def test_three_arg_range_negative_step_preserved(self, tmp_path):
-        # [10:0:-1] means start=10, step=0, end=-1 in internal storage
+        # [10:-1:0] means start=10, step=-1, end=0 in internal storage
         src = "x = [for (i=[10:-1:0]) i];"
         out = parse_and_print(tmp_path / "t.scad", src)
         assert "[10:-1:0]" in out