Make axisartist.clip_path pseudo-tests real.

The results seem to be acceptable.
matplotlib · efiring · Feb 9, 2018 · Dec 1, 2016 · Dec 1, 2016 · Dec 1, 2016
commit bc1bfab12150feaad88f0944dc1cda977452f577
diff --git a/lib/mpl_toolkits/axisartist/clip_path.py b/lib/mpl_toolkits/axisartist/clip_path.py
@@ -133,29 +133,3 @@ def clip_line_to_rect(xline, yline, bbox):
              if bbox.containsx(x)]
 
     return list(zip(lx4, ly4)), [c_left, c_bottom, c_right, c_top]
-
-
-if __name__ == "__main__":
-
-    import matplotlib.pyplot as plt
-
-    x = np.array([-3, -2, -1, 0., 1, 2, 3, 2, 1, 0, -1, -2, -3, 5])
-    #x = np.array([-3, -2, -1, 0., 1, 2, 3])
-    y = np.arange(len(x))
-    #x0 = 2
-
-    plt.plot(x, y, lw=1)
-
-    from matplotlib.transforms import Bbox
-    bb = Bbox.from_extents(-2, 3, 2, 12.5)
-    lxy, ticks = clip_line_to_rect(x, y, bb)
-    for xx, yy in lxy:
-        plt.plot(xx, yy, lw=1, color="g")
-
-    ccc = iter(["ro", "go", "rx", "bx"])
-    for ttt in ticks:
-        cc = next(ccc)
-        for (xx, yy), aa in ttt:
-            plt.plot([xx], [yy], cc)
-
-    #xlim(
diff --git a/lib/mpl_toolkits/tests/baseline_images/test_axisartist_clip_path/clip_path.png b/lib/mpl_toolkits/tests/baseline_images/test_axisartist_clip_path/clip_path.png
diff --git a/lib/mpl_toolkits/tests/test_axisartist_clip_path.py b/lib/mpl_toolkits/tests/test_axisartist_clip_path.py
@@ -0,0 +1,38 @@
+from __future__ import (absolute_import, division, print_function,
+                        unicode_literals)
+
+import six
+
+import numpy as np
+import matplotlib.pyplot as plt
+from matplotlib.testing.decorators import image_comparison
+from matplotlib.transforms import Bbox
+
+from mpl_toolkits.axisartist.clip_path import clip_line_to_rect
+
+
+@image_comparison(baseline_images=['clip_path'],
+                  extensions=['png'], style='default')
+def test_clip_path():
+    x = np.array([-3, -2, -1, 0., 1, 2, 3, 2, 1, 0, -1, -2, -3, 5])
+    y = np.arange(len(x))
+
+    fig, ax = plt.subplots()
+    ax.plot(x, y, lw=1)
+
+    bbox = Bbox.from_extents(-2, 3, 2, 12.5)
+    rect = plt.Rectangle(bbox.p0, bbox.width, bbox.height,
+                         facecolor='none', edgecolor='k', ls='--')
+    ax.add_patch(rect)
+
+    clipped_lines, ticks = clip_line_to_rect(x, y, bbox)
+    for lx, ly in clipped_lines:
+        ax.plot(lx, ly, lw=1, color='C1')
+        for px, py in zip(lx, ly):
+            assert bbox.contains(px, py)
+
+    ccc = iter(['C3o', 'C2x', 'C3o', 'C2x'])
+    for ttt in ticks:
+        cc = six.next(ccc)
+        for (xx, yy), aa in ttt:
+            ax.plot([xx], [yy], cc)