tests: Add some optional hypothesis tests

.gitignore

@@ -18,6 +18,7 @@
 .cache
 MANIFEST
 dist
+.hypothesis
 
 # image files
 *.pdf

tests/test_hypothesis.py

@@ -0,0 +1,42 @@
+# -*- coding: utf-8 -*-
+
+import math
+
+import pytest
+import cairo
+
+pytest.importorskip("hypothesis")
+from hypothesis import given, strategies, assume
+
+
+@given(strategies.floats(), strategies.floats())
+def test_surface_set_device_scale(x_scale, y_scale):
+    assume(not any(math.isnan(v) for v in [x_scale, y_scale]))
+
+    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 10, 10)
+    try:
+        surface.set_device_scale(x_scale, y_scale)
+    except cairo.Error as e:
+        assert e.status == cairo.Status.INVALID_MATRIX
+    else:
+        assert surface.get_device_scale() == (x_scale, y_scale)
+
+
+@given(strategies.floats(), strategies.floats())
+def test_surface_set_device_offset(x_offset, y_offset):
+    assume(not any(math.isnan(v) for v in [x_offset, y_offset]))
+
+    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 10, 10)
+    surface.set_device_offset(x_offset, y_offset)
+
+
+@given(strategies.floats(), strategies.floats(), strategies.floats(),
+       strategies.floats())
+def test_surface_create_for_rectangle(x, y, w, h):
+    assume(not any(math.isnan(v) for v in [x, y, w, h]))
+
+    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 100, 100)
+    try:
+        surface.create_for_rectangle(x, y, w, h)
+    except cairo.Error as e:
+        assert e.status == cairo.Status.INVALID_SIZE