diff --git a/data_structures/arrays/sudoku_solver.py b/data_structures/arrays/sudoku_solver.py
index 7e38e1465..fd1a4f3e3 100644
--- a/data_structures/arrays/sudoku_solver.py
+++ b/data_structures/arrays/sudoku_solver.py
@@ -23,7 +23,7 @@ unitlist = (
     + [cross(rs, cs) for rs in ("ABC", "DEF", "GHI") for cs in ("123", "456", "789")]
 )
 units = {s: [u for u in unitlist if s in u] for s in squares}
-peers = {s: set(sum(units[s], [])) - {s} for s in squares}  # noqa: RUF017
+peers = {s: {x for u in units[s] for x in u} - {s} for s in squares}
 
 
 def test():
@@ -172,7 +172,8 @@ def solved(values):
 
 def from_file(filename, sep="\n"):
     "Parse a file into a list of strings, separated by sep."
-    return open(filename).read().strip().split(sep)
+    with open(filename) as file:
+        return file.read().strip().split(sep)
 
 
 def random_puzzle(assignments=17):
diff --git a/geometry/geometry.py b/geometry/geometry.py
index 9e353dee1..a0be8eb3b 100644
--- a/geometry/geometry.py
+++ b/geometry/geometry.py
@@ -48,6 +48,18 @@ class Side:
     Side(length=5, angle=Angle(degrees=45.6), next_side=None)
     >>> Side(5, Angle(45.6), Side(1, Angle(2)))  # doctest: +ELLIPSIS
     Side(length=5, angle=Angle(degrees=45.6), next_side=Side(length=1, angle=Angle(d...
+    >>> Side(-1)
+    Traceback (most recent call last):
+        ...
+    TypeError: length must be a positive numeric value.
+    >>> Side(5, None)
+    Traceback (most recent call last):
+        ...
+    TypeError: angle must be an Angle object.
+    >>> Side(5, Angle(90), "Invalid next_side")
+    Traceback (most recent call last):
+        ...
+    TypeError: next_side must be a Side or None.
     """
 
     length: float
@@ -162,6 +174,19 @@ class Polygon:
 
     >>> Polygon()
     Polygon(sides=[])
+    >>> polygon = Polygon()
+    >>> polygon.add_side(Side(5)).get_side(0)
+    Side(length=5, angle=Angle(degrees=90), next_side=None)
+    >>> polygon.get_side(1)
+    Traceback (most recent call last):
+        ...
+    IndexError: list index out of range
+    >>> polygon.set_side(0, Side(10)).get_side(0)
+    Side(length=10, angle=Angle(degrees=90), next_side=None)
+    >>> polygon.set_side(1, Side(10))
+    Traceback (most recent call last):
+        ...
+    IndexError: list assignment index out of range
     """
 
     sides: list[Side] = field(default_factory=list)
@@ -207,6 +232,10 @@ class Rectangle(Polygon):
     30
     >>> rectangle_one.area()
     50
+    >>> Rectangle(-5, 10)
+    Traceback (most recent call last):
+        ...
+    TypeError: length must be a positive numeric value.
     """
 
     def __init__(self, short_side_length: float, long_side_length: float) -> None: