Update currency documentation and enhance pretty_price_range tests for consistency

Author: ahosgood

docs/currency.md

@@ -72,11 +72,11 @@ Formats a price range.
 from tna_utilities.currency import pretty_price_range
 
 print(pretty_price_range(5, 10))
-# £5.00 to £10
+# £5 to £10
 
 print(pretty_price_range(0, 15))
-# Free to £15.00
+# Free to £15
 
 print(pretty_price_range(10, 0))
-# From £10.00
+# From £10
 ```

tests/test_currency.py

@@ -88,6 +88,13 @@ def test_happy(self):
         self.assertEqual(pretty_price_range(5, 0), "From £5")
         self.assertEqual(pretty_price_range(5, 10), "£5 to £10")
         self.assertEqual(pretty_price_range(10, 5), "£5 to £10")
+        self.assertEqual(pretty_price_range(10, 0), "From £10")
+        self.assertEqual(pretty_price_range(0, 5, False), "Free to £5.00")
+        self.assertEqual(pretty_price_range(5, 10, False), "£5.00 to £10.00")
+        self.assertEqual(pretty_price_range(5, 0, False), "From £5.00")
+        self.assertEqual(pretty_price_range(5, 1, False), "£1.00 to £5.00")
+
+    def test_unhappy(self):
         with self.assertRaises(ValueError):
             pretty_price_range(5, "a")
         with self.assertRaises(TypeError):