WiP: Convert camera tests to Hypothesis

ppb/testutils.py

@@ -1,11 +1,29 @@
 import time
 from typing import Callable
 
+from hypothesis import strategies as st
+
+from ppb import Vector
 from ppb.engine import GameEngine
 from ppb.events import Quit
 from ppb.systems import System
 
 
+def integer_vectors(min_value=None, max_value=None):
+    return st.builds(
+        Vector,
+        st.integers(min_value=min_value, max_value=max_value),
+        st.integers(min_value=min_value, max_value=max_value),
+    )
+
+def vectors(max_magnitude=1e75):
+    return st.builds(
+        Vector,
+        st.floats(min_value=-max_magnitude, max_value=max_magnitude),
+        st.floats(min_value=-max_magnitude, max_value=max_magnitude),
+    )
+
+
 class Failer(System):
 
     def __init__(self, *, fail: Callable[[GameEngine], bool], message: str,

requirements-tests.txt

@@ -1 +1,2 @@
+hypothesis
 pytest

tests/test_camera.py

@@ -1,21 +1,30 @@
+from hypothesis import given, note, strategies as st
+
 from ppb import BaseSprite
 from ppb import Vector
 from ppb.camera import Camera
+from ppb.testutils import integer_vectors, vectors
+
+
+ONE_K = 1024
+ONE_M = ONE_K * ONE_K
 
 
-def test_camera_move():
-    cam = Camera()
-    cam.position = Vector(500, 500)
-    assert cam.position == Vector(500, 500)
-    cam.position += Vector(100, 100)
-    assert cam.position == Vector(600, 600)
+def cameras():
+    return st.builds(
+        lambda offset, diagonal: Camera(viewport=(*offset, *(offset+diagonal))),
+        integer_vectors(min_value=-ONE_M, max_value=ONE_M),
+        integer_vectors(min_value=2, max_value=ONE_M),
+    )
 
 
-def test_camera_viewport():
-    cam = Camera(viewport=(0, 0, 800, 600))
-    assert cam.point_in_viewport(Vector(400, 400))
-    assert not cam.point_in_viewport(Vector(900, 600))
-    assert cam.viewport_offset == Vector(400, 300)
+@given(diagonal=integer_vectors(min_value=2, max_value=ONE_M))
+def test_camera_viewport(diagonal: Vector):
+    x, y = diagonal
+    cam = Camera(viewport=(0, 0, x, y))
+    assert cam.point_in_viewport(0.5 * diagonal)
+    assert not cam.point_in_viewport(diagonal + (100, 100))
+    assert cam.viewport_offset == 0.5 * diagonal
 
 
 def test_camera_point_in_viewport_not_at_origin():
@@ -26,6 +35,13 @@ def test_camera_point_in_viewport_not_at_origin():
     assert not cam.point_in_viewport(Vector(901, 600))
 
 
+@given(cam=cameras(), v=vectors())
+def test_camera_roundtrip_frame_viewport(cam: Camera, v: Vector):
+    """Check that Camera.translate_to_{frame,viewport} are inverse of one another."""
+    assert cam.translate_to_frame(cam.translate_to_viewport(v)).isclose(v)
+    assert cam.translate_to_viewport(cam.translate_to_frame(v)).isclose(v)
+
+
 def test_camera_translate_to_frame():
     cam = Camera(viewport=(0, 0, 800, 600), pixel_ratio=80)
     assert cam.position == Vector(0, 0)
@@ -70,4 +86,4 @@ def test_viewport_change_affects_frame_height():
     cam = Camera(viewport=(0, 0, 800, 600), pixel_ratio=80)
     assert cam.frame_left == -5
     cam.viewport_width = 400
-    assert cam.frame_left == -2.5
+    assert cam.frame_left == -2.5