Add testing for preprocessing using hypothesis

skan/test/test_pre.py

@@ -0,0 +1,41 @@
+from scipy import special
+import numpy as np
+from hypothesis import given, strategies
+from hypothesis.extra.numpy import arrays
+
+from skan import pre
+
+def ball_volume(ndim, radius):
+    """Return the volume of a ball of dimension `ndim` and radius `radius`."""
+    n = ndim
+    r = radius
+    return np.pi ** (n / 2) / special.gamma(n / 2 + 1) * r ** n
+
+
+@given(strategies.integers(min_value=1, max_value=4),
+       strategies.integers(min_value=2, max_value=10))
+def test_hyperball_volume(ndim, radius):
+    theoretical_volume = ball_volume(ndim, radius)
+    approximate_volume = np.sum(pre.hyperball(ndim, radius))
+    np.testing.assert_allclose(approximate_volume, theoretical_volume,
+                               rtol=0.5)
+
+
+uint8s = strategies.integers(min_value=0, max_value=255)
+
+
+@given(image=arrays(dtype=np.uint8, shape=(15, 15)),
+       sigma=strategies.integers(min_value=0, max_value=3),
+       radius=strategies.integers(min_value=0, max_value=6))
+def test_threshold2d(image, sigma, radius):
+    radius = max(radius, 2 * sigma)
+    thresholded0 = pre.threshold(image, sigma=sigma, radius=radius)
+    assert thresholded0.dtype == bool
+    assert thresholded0.shape == image.shape
+    offset = np.random.randint(-15, 15)
+    thresholded1 = pre.threshold(image, sigma=sigma, radius=radius,
+                                 offset=offset)
+    if offset > 0:
+        assert np.all(thresholded1 <= thresholded0)
+    else:
+        assert np.all(thresholded1 >= thresholded0)

test-environment.yml

@@ -13,3 +13,5 @@ dependencies:
 - pytest>=3*
 - coverage>=4.0
 - pytest-cov>=2.2
+pip:
+  - hypothesis>=3.6

test-requirements.txt

@@ -1,3 +1,4 @@
 pytest>=3.0
 pytest-cov>=2.3
 coverage>=4.2
+hypothesis>=3.6