adjusting error bounds more

Author: pavelkomarov

pynumdiff/tests/test_diff_methods.py

@@ -225,7 +225,7 @@ def spline_irreg_step(*args, **kwargs): return splinediff(*args, **kwargs)
               [(0, 0), (3, 3), (0, 0), (3, 3)]],
     robustdiff: [[(-15, -15), (-14, -14), (0, -1), (0, 0)],
                  [(-14, -14), (-13, -14), (0, -1), (0, 0)],
-                 [(-14, -14), (-13, -14), (0, -1), (0, 0)],
+                 [(-14, -14), (-13, -13), (0, -1), (0, 0)],
                  [(-1, -1), (0, 0), (0, -1), (1, 0)],
                  [(0, 0), (1, 1), (0, 0), (1, 1)],
                  [(1, 1), (3, 3), (1, 1), (3, 3)]],