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eferro/specs/harry_potter_kata_spec.py

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+# -*- coding: utf-8 -*-
+
+from expects import *
+from hamcrest import *
+from doublex import *
+
+from collections import Counter
+
+UNIT_PRICE = 8
+BOOK1 = 'book1'
+BOOK2 = 'book2'
+BOOK3 = 'book3'
+
+def books_price(books):
+    discounts = {
+        2: 0.95,
+        3: 0.90,
+    }
+    book_counter = Counter(books)
+    differents = len(book_counter.keys())
+    repeated = len(books)-differents
+
+    return differents * discounts.get(differents, 1) * UNIT_PRICE + repeated * UNIT_PRICE
+
+with context('Harry Potter Kata'):
+
+    with describe('buying one by one'):
+        with it('the cost of the first is UNIT_PRICE'):
+            expect(books_price([BOOK1])).to(equal(UNIT_PRICE))
+        with it('the cost of the second is UNIT_PRICE'):
+            expect(books_price([BOOK2])).to(equal(UNIT_PRICE))
+
+    with describe('buying two'):
+        with it('the cost of two copys of the same book is twice the unit price'):
+            expect(books_price([BOOK1, BOOK1])).to(equal(16))
+            expect(books_price([BOOK2, BOOK2])).to(equal(16))
+
+        with it('the cost of two different books has a 5percent discount'):
+            expect(books_price([BOOK1, BOOK2])).to(equal(16*0.95))
+            expect(books_price([BOOK2, BOOK1])).to(equal(16*0.95))
+
+    with describe('buying three books'):
+        with it('the cost of three copies is 24'):
+            expect(books_price([BOOK1, BOOK1, BOOK1])).to(equal(24))
+
+        with describe('when two book are different'):
+            with it('the cost is 23.5 (two books with 5percent discount)'):
+                expect(books_price([BOOK1, BOOK1, BOOK2])).to(equal(16*0.95 + UNIT_PRICE))
+        with describe('when all are differents'):
+            with it('the cost is 21.6 (three books with 10percent discount)'):
+                expect(books_price([BOOK1, BOOK2, BOOK3])).to(equal(UNIT_PRICE * 3*0.90))
+
+    with describe('buing four books'):
+        with it('the cost of four copies is 32'):
+            expect(books_price([BOOK1, BOOK1, BOOK1, BOOK1])).to(equal(32))