Add tests for CustomDecimalField

gracedb/api/v1/tests/test_fields.py

+from __future__ import absolute_import
+import decimal
+import math
+
+from django.test import SimpleTestCase
+
+from ..fields import CustomDecimalField
+
+
+class TestCustomDecimalField(SimpleTestCase):
+    """
+    Test different conversions of floats to decimal.Decimals using
+    CustomDecimalField. This class is only different from the default
+    DecimalField provided by rest_framework for floats, so we don't need to
+    test other data types.
+    """
+
+    def test_lots_of_floats(self):
+        # Setup
+        DECIMAL_PLACES = 6
+        raw_int = 1234567890
+
+        MAX_DIGITS = int(math.ceil(math.log10(raw_int))) + DECIMAL_PLACES
+        df = CustomDecimalField(MAX_DIGITS, DECIMAL_PLACES)
+        for exp in range(0, DECIMAL_PLACES):
+            for num in range(0, 10):
+                decimal_places_as_int = num * (10**exp)
+                raw_float = raw_int + decimal_places_as_int * \
+                    (10**(-1*DECIMAL_PLACES))
+                raw_str = str(raw_int) + '.' + '{{:0>{dp}}}'.format(
+                    dp=DECIMAL_PLACES).format(decimal_places_as_int)
+                output = df.to_internal_value(raw_float)
+                self.assertEqual(output.to_eng_string(), raw_str)
+