PriceRule + tests

Siddharta Govindaraj · Siddharta Govindaraj · commit e8433faf6f44 · 2015-03-23T10:36:10.000+05:30
diff --git a/stock_alerter/rule.py b/stock_alerter/rule.py
@@ -0,0 +1,17 @@
+class PriceRule:
+    """PriceRule is a rule that triggers when a stock price satisfies a
+    condition (usually greater, equal or lesser than a given value)"""
+
+    def __init__(self, symbol, condition):
+        self.symbol = symbol
+        self.condition = condition
+
+    def matches(self, exchange):
+        try:
+            stock = exchange[self.symbol]
+        except KeyError:
+            return False
+        return self.condition(stock) if stock.price else False
+
+    def depends_on(self):
+        return {self.symbol}
diff --git a/stock_alerter/tests/test_rule.py b/stock_alerter/tests/test_rule.py
@@ -0,0 +1,34 @@
+import unittest
+from datetime import datetime
+
+from ..stock import Stock
+from ..rule import PriceRule
+
+
+class PriceRuleTest(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        goog = Stock("GOOG")
+        goog.update(datetime(2014, 2, 10), 11)
+        cls.exchange = {"GOOG": goog}
+
+    def test_a_PriceRule_matches_when_it_meets_the_condition(self):
+        rule = PriceRule("GOOG", lambda stock: stock.price > 10)
+        self.assertTrue(rule.matches(self.exchange))
+
+    def test_a_PriceRule_is_False_if_the_condition_is_not_met(self):
+        rule = PriceRule("GOOG", lambda stock: stock.price < 10)
+        self.assertFalse(rule.matches(self.exchange))
+
+    def test_a_PriceRule_is_False_if_the_stock_is_not_in_the_exchange(self):
+        rule = PriceRule("MSFT", lambda stock: stock.price > 10)
+        self.assertFalse(rule.matches(self.exchange))
+
+    def test_a_PriceRule_is_False_if_the_stock_hasnt_got_an_update_yet(self):
+        self.exchange["AAPL"] = Stock("AAPL")
+        rule = PriceRule("AAPL", lambda stock: stock.price > 10)
+        self.assertFalse(rule.matches(self.exchange))
+
+    def test_a_PriceRule_only_depends_on_its_stock(self):
+        rule = PriceRule("MSFT", lambda stock: stock.price > 10)
+        self.assertEqual({"MSFT"}, rule.depends_on())
