fix for get_x_bits plus tests

probables/utilities.py

@@ -23,5 +23,5 @@ def get_x_bits(num, max_bits, num_bits, right_bits=True):
     bits = bin(num).lstrip('0b')
     bits = bits.zfill(max_bits)
     if right_bits:
-        return int(bits[num_bits:], 2)
+        return int(bits[-num_bits:], 2)
     return int(bits[:num_bits], 2)

tests/test_utilities.py

@@ -0,0 +1,71 @@
+from __future__ import (unicode_literals, absolute_import, print_function)
+import unittest
+import os
+
+from . utilities import (different_hash)
+from probables.utilities import (is_hex_string, is_valid_file, get_x_bits)
+
+class TestProbablesUtilities(unittest.TestCase):
+
+    def test_is_hex(self):
+        ''' test the is valid hex function '''
+        self.assertTrue(is_hex_string('1234678909abcdef'))
+        self.assertTrue(is_hex_string('1234678909ABCDEF'))
+        self.assertFalse(is_hex_string('1234678909abcdfq'))
+        self.assertFalse(is_hex_string('1234678909ABCDEFQ'))
+
+    def test_is_valid_file(self):
+        ''' test the is valid file function '''
+        self.assertFalse(is_valid_file(None))
+        self.assertFalse(is_valid_file('./file_doesnt_exist.txt'))
+        filename = './create_this_file.txt'
+        with open(filename, 'w'):
+            pass
+        self.assertTrue(is_valid_file(filename))
+        os.remove(filename)
+
+    def test_get_x_bits(self):
+        ''' test the get x bits function '''
+        for i in range(8):
+            res = get_x_bits(i, 4, 2, True)
+            self.assertEqual(res, i % 4)
+        for i in range(8):
+            res = get_x_bits(i, 4, 2, False)
+            if i < 4:
+                self.assertEqual(res, 0)
+            else:
+                self.assertEqual(res, 1)
+
+    def test_get_x_bits_large(self):
+        ''' test it on much larger numbers '''
+        res = different_hash('this is a test', 1)[0]
+        # 1010100101011011100100010101010011110000001010011010000101001011
+        t1 = get_x_bits(res, 64, 32, True)
+        t2 = get_x_bits(res, 64, 32, False)
+        self.assertEqual(4029260107, t1)
+        self.assertEqual(2841350484, t2)
+
+        t1 = get_x_bits(res, 64, 16, True)
+        t2 = get_x_bits(res, 64, 16, False)
+        self.assertEqual(41291, t1)
+        self.assertEqual(43355, t2)
+
+        t1 = get_x_bits(res, 64, 8, True)
+        t2 = get_x_bits(res, 64, 8, False)
+        self.assertEqual(75, t1)
+        self.assertEqual(169, t2)
+
+        t1 = get_x_bits(res, 64, 4, True)
+        t2 = get_x_bits(res, 64, 4, False)
+        self.assertEqual(11, t1)
+        self.assertEqual(10, t2)
+
+        t1 = get_x_bits(res, 64, 2, True)
+        t2 = get_x_bits(res, 64, 2, False)
+        self.assertEqual(3, t1)
+        self.assertEqual(2, t2)
+
+        t1 = get_x_bits(res, 64, 1, True)
+        t2 = get_x_bits(res, 64, 1, False)
+        self.assertEqual(1, t1)
+        self.assertEqual(1, t2)