tests: Uniformize single-letter variable names

- x, y, ... are vectors
- l, m, ... are scalars

Closes #75

tests/test_vector2_normalize.py

@@ -5,9 +5,9 @@
 import ppb_vector
 
 
-@given(v=vectors())
-def test_normalize_length(v):
-    """v.normalize().length == 1 and v == v.length * v.normalize()"""
-    assume(v != (0, 0))
-    assert isclose(v.normalize().length, 1)
-    assert v.isclose(v.length * v.normalize())
+@given(x=vectors())
+def test_normalize_length(x):
+    """x.normalize().length == 1 and x == x.length * x.normalize()"""
+    assume(x != (0, 0))
+    assert isclose(x.normalize().length, 1)
+    assert x.isclose(x.length * x.normalize())

tests/test_vector2_rotate.py

@@ -94,24 +94,28 @@ def test_rotation_stability2(initial, angles):
     assert math.isclose(fellswoop.length, initial.length, rel_tol=1e-15)
 
 
-@given(a=vectors(), b=vectors(), l=floats(), angle=angles())
+@given(
+    x=vectors(), y=vectors(),
+    l=floats(),
+    angle=angles(),
+)
 # In this example:
-# * a * l == -b
+# * x * l == -y
 # * Rotation must not be an multiple of 90deg
 # * Must be sufficiently large
 @example(
-    a=Vector2(1e10, 1e10),
-    b=Vector2(1e19, 1e19),
+    x=Vector2(1e10, 1e10),
+    y=Vector2(1e19, 1e19),
     l=-1e9,
     angle=45,
 )
-def test_rotation_linearity(a, b, l, angle):
-    """(l*a + b).rotate is equivalent to l*a.rotate + b.rotate"""
-    inner = (l * a + b).rotate(angle)
-    outer = l * a.rotate(angle) + b.rotate(angle)
-    note(f"l * a + b: {l * a + b}")
-    note(f"l * a.rotate(): {l * a.rotate(angle)}")
-    note(f"b.rotate(): {b.rotate(angle)}")
+def test_rotation_linearity(x, y, l, angle):
+    """(l*x + y).rotate is equivalent to l*x.rotate + y.rotate"""
+    inner = (l * x + y).rotate(angle)
+    outer = l * x.rotate(angle) + y.rotate(angle)
+    note(f"l * x + y: {l * x + y}")
+    note(f"l * x.rotate(): {l * x.rotate(angle)}")
+    note(f"y.rotate(): {y.rotate(angle)}")
     note(f"Inner: {inner}")
     note(f"Outer: {outer}")
-    assert inner.isclose(outer, rel_to=[a, l * a, b])
+    assert inner.isclose(outer, rel_to=[x, l * x, y])

tests/test_vector2_scalar_multiplication.py

@@ -12,11 +12,15 @@ def test_scalar_coordinates(scalar: float, vector: Vector2):
     assert scalar * vector.y == (scalar * vector).y
 
 
-@given(x=floats(), y=floats(), v=vectors())
-def test_scalar_associative(x: float, y: float, v: Vector2):
-    """(x * y) * v == x * (y * v)"""
-    left  = (x * y) * v
-    right =  x * (y * v)
+@given(
+    l=floats(),
+    m=floats(),
+    x=vectors()
+)
+def test_scalar_associative(l: float, m: float, x: Vector2):
+    """(l * m) * x == l * (m * x)"""
+    left  = (l * m) * x
+    right =  l * (m * x)
     assert left.isclose(right)
 
 @given(l=floats(), x=vectors(), y=vectors())