add a Cypher System dice rolling library method

not available to the bot, yet, but that's next

Signed-off-by: Brian S. Stephan <bss@incorporeal.org>

tests/test_dice_lib.py

@@ -0,0 +1,77 @@
+"""Tests for dice operations."""
+from unittest import mock
+
+from django.test import TestCase
+
+import dice.lib
+
+
+class DiceLibTestCase(TestCase):
+    """Test that a variety of dice rolls work as expected."""
+
+    def test_cypher_rolls(self):
+        """Roll a variety of Cypher System rolls."""
+        # simple task, simple check
+        with mock.patch('random.SystemRandom.randint', return_value=5):
+            result = dice.lib.cypher_roll(difficulty=1)
+        self.assertEqual(result, (5, 1, True, None))
+
+        # simple failure
+        with mock.patch('random.SystemRandom.randint', return_value=2):
+            result = dice.lib.cypher_roll(difficulty=1)
+        self.assertEqual(result, (2, 0, False, None))
+
+        # rolled a 1
+        with mock.patch('random.SystemRandom.randint', return_value=1):
+            result = dice.lib.cypher_roll(difficulty=1)
+        self.assertEqual(result, (1, None, False, 'a GM intrusion'))
+
+        # rolled a 17
+        with mock.patch('random.SystemRandom.randint', return_value=17):
+            result = dice.lib.cypher_roll(difficulty=1)
+        self.assertEqual(result, (17, 5, True, '+1 damage'))
+
+        # rolled a 18
+        with mock.patch('random.SystemRandom.randint', return_value=18):
+            result = dice.lib.cypher_roll(difficulty=1)
+        self.assertEqual(result, (18, 6, True, '+2 damage'))
+
+        # rolled a 19
+        with mock.patch('random.SystemRandom.randint', return_value=19):
+            result = dice.lib.cypher_roll(difficulty=1)
+        self.assertEqual(result, (19, 6, True, 'a minor effect'))
+
+        # rolled a 20
+        with mock.patch('random.SystemRandom.randint', return_value=20):
+            result = dice.lib.cypher_roll(difficulty=1)
+        self.assertEqual(result, (20, 6, True, 'a MAJOR EFFECT'))
+
+        # mods affect the result of what the roll beats
+        with mock.patch('random.SystemRandom.randint', return_value=2):
+            result = dice.lib.cypher_roll(difficulty=1, mods='-5')
+        self.assertEqual(result, (2, 5, True, None))
+
+        # complex mods
+        with mock.patch('random.SystemRandom.randint', return_value=2):
+            result = dice.lib.cypher_roll(difficulty=3, mods='+1-4')
+        self.assertEqual(result, (2, 3, True, None))
+
+        # complex mods
+        with mock.patch('random.SystemRandom.randint', return_value=2):
+            result = dice.lib.cypher_roll(difficulty=3, mods='-4+1')
+        self.assertEqual(result, (2, 3, True, None))
+
+        # ...even without a difficulty known
+        with mock.patch('random.SystemRandom.randint', return_value=2):
+            result = dice.lib.cypher_roll(mods='-5')
+        self.assertEqual(result, (2, 5, None, None))
+
+        # general "don't know the difficulty" kind of check
+        with mock.patch('random.SystemRandom.randint', return_value=10):
+            result = dice.lib.cypher_roll(mods='-2')
+        self.assertEqual(result, (10, 5, None, None))
+
+        # general "don't know the difficulty" kind of check in the other direction
+        with mock.patch('random.SystemRandom.randint', return_value=10):
+            result = dice.lib.cypher_roll(mods='2')
+        self.assertEqual(result, (10, 1, None, None))