Add tests for crontab changes.

Refs #603

docs/api.rst

@@ -1109,7 +1109,7 @@ Huey object
         of an unhandled exception in the parent task.
 
 
-.. py:function:: crontab(month='*', day='*', day_of_week='*', hour='*', minute='*')
+.. py:function:: crontab(month='*', day='*', day_of_week='*', hour='*', minute='*'[, strict=False])
 
     Convert a "crontab"-style set of parameters into a test function that will
     return ``True`` when a given ``datetime`` matches the parameters set forth in
@@ -1124,6 +1124,8 @@ Huey object
     - "m-n" = run every time m..n
     - "m,n" = run on m and n
 
+    :param bool strict: cause crontab to raise a ``ValueError`` if an input
+       does not match a supported input format.
     :rtype: a test function that takes a ``datetime`` and returns a boolean
 
     .. note::

huey/tests/test_crontab.py

@@ -118,3 +118,9 @@ def test_invalid_crontabs(self):
         self.assertRaises(ValueError, crontab, minute='61')
         self.assertRaises(ValueError, crontab, minute='0-61')
         self.assertRaises(ValueError, crontab, day_of_week='*/3')
+
+    def test_invalid_crontabs_2(self):
+        self.assertTrue(crontab(minute='*abc'))
+        invalid = ('abc', '*abc', 'a-b', '1-c', '0x9')
+        for i in invalid:
+            self.assertRaises(ValueError, crontab, minute=i, strict=True)