Added badly constructed range handling

sqlalchemy_utils/__init__.py

@@ -6,6 +6,7 @@ from .types import (
     PhoneNumber,
     PhoneNumberType,
     NumberRange,
+    NumberRangeException,
     NumberRangeRawType,
     NumberRangeType
 )
@@ -20,6 +21,7 @@ __all__ = (
     InstrumentedList,
     Merger,
     NumberRange,
+    NumberRangeException,
     NumberRangeRawType,
     NumberRangeType,
     PhoneNumber,

sqlalchemy_utils/types.py

@@ -90,8 +90,18 @@ class NumberRangeType(types.TypeDecorator):
         return NumberRange.from_normalized_str(value)
 
 
+class NumberRangeException(Exception):
+    def __init__(self, min_value, max_value):
+        self.message = 'Min value %d is bigger than max value %d.' % (
+            min_value,
+            max_value
+        )
+
+
 class NumberRange(object):
     def __init__(self, min_value, max_value):
+        if min_value > max_value:
+            raise NumberRangeException(min_value, max_value)
         self.min_value = min_value
         self.max_value = max_value
 

tests/test_number_range.py

@@ -1,5 +1,6 @@
 import sqlalchemy as sa
-from sqlalchemy_utils import NumberRangeType, NumberRange
+from pytest import raises
+from sqlalchemy_utils import NumberRangeType, NumberRange, NumberRangeException
 from tests import DatabaseTestCase
 
 
@@ -34,3 +35,7 @@ class TestNumberRange(object):
 
     def test_str_representation(self):
         assert str(NumberRange(1, 3)) == '[1, 3]'
+
+    def test_raises_exception_for_badly_constructed_range(self):
+        with raises(NumberRangeException):
+            NumberRange(3, 2)