Some more tests, doc

pyramid/arima/tests/test_arima.py

@@ -233,6 +233,13 @@ def test_many_orders():
                suppress_warnings=True, stepwise=True)
 
 
+def test_small_samples():
+    # if n_samples < 10, test the new starting p, d, Q
+    samp = lynx[:8]
+    auto_arima(samp, suppress_warnings=True, stepwise=True,
+               error_action='ignore')
+
+
 def test_with_seasonality1():
     fit = ARIMA(order=(1, 1, 1),
                 seasonal_order=(0, 1, 1, 12),

pyramid/arima/tests/test_stationarity.py

@@ -1,4 +1,4 @@
-# stationarity tests
+# stationarity/seasonality tests
 
 from __future__ import absolute_import
 from numpy.testing import assert_array_almost_equal, assert_almost_equal
@@ -114,6 +114,16 @@ def test_ch_test():
     # this won't even go thru because n < 2 * m + 5:
     assert CHTest(m=365).estimate_seasonal_differencing_term(austres) == 0
 
+    # change the length to be longer so we can actually test the end case
+    aus_list = austres.tolist()  # type: list
+    y = np.asarray(aus_list * 10)  # type: np.ndarray
+
+    # y len is now 1760, which is > 2 * m + 5, but idk what to assert
+    CHTest(m=365).estimate_seasonal_differencing_term(y)
+
+    # what if m > 365???
+    CHTest(m=366).estimate_seasonal_differencing_term(y)
+
 
 def test_ch_base():
     test = CHTest(m=2)

pyramid/utils/array.py

@@ -200,6 +200,28 @@ def is_iterable(x):
     x : str, iterable or object
         The object in question.
 
+    Examples
+    --------
+    Strings and other objects are not iterable:
+
+    >>> x = "not me"
+    >>> y = 123
+    >>> any(is_iterable(v) for v in (x, y))
+    False
+
+    Tuples, lists and other structures with ``__iter__`` are:
+
+    >>> x = ('a', 'tuple')
+    >>> y = ['a', 'list']
+    >>> all(is_iterable(v) for v in (x, y))
+    True
+
+    This even applies to numpy arrays:
+
+    >>> import numpy as np
+    >>> is_iterable(np.arange(10))
+    True
+
     Returns
     -------
     isiter : bool