implement pretty printing for IPython

...by implementing _repr_pretty_() which is used by IPython.lib.pretty.
add IPython test dependency so that this can be tested.

requirements-test.txt

@@ -1,3 +1,4 @@
 flake8
+IPython>=4.2.1
 pytest>=3
 pytest-cov

src/sanest/sanest.py

@@ -420,6 +420,15 @@ def _truncated_repr(self):
         return '{}.{.__name__}({})'.format(
             __package__, type(self), reprlib.repr(self._data))
 
+    def _repr_pretty_(self, p, cycle):
+        """Helper for pretty-printing in IPython."""
+        opening = '{}.{.__name__}('.format(__package__, type(self))
+        if cycle:  # pragma: no cover
+            p.text(opening + '...)')
+        else:
+            with p.group(len(opening), opening, ')'):
+                p.pretty(self._data)
+
     def __copy__(self):
         cls = type(self)
         obj = cls.__new__(cls)

test_sanest.py

@@ -9,6 +9,7 @@
 import sys
 import textwrap
 
+import IPython.lib.pretty
 import pytest
 
 import sanest
@@ -1659,3 +1660,9 @@ def dedent(s):
 def test_pretty_printing_pprint(input, expected):
     actual = pprint.pformat(input)
     assert actual == expected
+
+
+@pytest.mark.parametrize(('input', 'expected'), PRETTY_PRINT_SAMPLES)
+def test_pretty_printing_ipython(input, expected):
+    actual = IPython.lib.pretty.pretty(input)
+    assert actual == expected