Finished Memory tests.

Added comment to memory class.
Added convenient method to memory class.

hardware/memory.py

@@ -3,23 +3,53 @@
 class Memory:
     def __init__(self,length=1024):
         self.cells = []
-        for i in length:
+        for i in range(length):
             self.cells.append(Cell())
 
-    def length(self):
+    def __len__(self):
         return len(self.cells)
 
+    def length(self):
+        #Return the size of the memory or number of cells
+        return len(self)
+
+    def cellAt(self,index):
+        #Returns the cell at position 'index'
+        try:
+            return self.cells[index]
+        except IndexError:
+            raise OutOfRange()
+
     def write(self,index,data):
-        cell = self.cells[index]
+        #Writes the 'data' in cell at position 'index'
+        cell = self.cellAt(index)
         cell.write(data)
+
+    def onUse(self,index):
+        #Sets on use the cell at position 'index'
+        cell = self.cellAt(index)
         cell.onUse()
 
+    def release(self,index):
+        #See 'free' method
+        self.free(index)
+
+    def free(self,index):
+        #Release the cell at position 'index'
+        cell = self.cellAt(index)
+        cell.free()
+
     def read(self,index):
-        cell =  self.cells[index]
+        #Returns the data of the cell at positioin 'index'
+        cell =  self.cellAt(index)
         return cell.read()
 
     def isInUse(self,index):
-        cell = self.cells[index]
+        """
+        Returns True if the cell at position 'index' has been setted as 'onUse',
+          otherwise returns False
+        """
+        cell = self.cellAt(index)
         return cell.isInUse()
 
 class Cell:
@@ -42,3 +72,8 @@ def onUse(self):
     def free(self):
         self.__inUse=False
 
+#Exceptions
+
+class OutOfRange(Exception):
+    def __str__(self):
+        return "there isn't a cell on this 'index'"

test/cellTest.py

@@ -4,7 +4,7 @@
 from mockito import *
 from hardware.memory import Cell
 
-class TestCell(unittest.TestCase):
+class CellTest(unittest.TestCase):
 
     def setUp(self):
         self.cell = Cell()
@@ -40,5 +40,5 @@ def test_WhenSetFreeThenIsInUseReturnsFalse(self):
 
         self.assertFalse(self.cell.isInUse())
 
-suite = unittest.TestLoader().loadTestsFromTestCase(TestCell)
+suite = unittest.TestLoader().loadTestsFromTestCase(CellTest)
 unittest.TextTestRunner(verbosity=2).run(suite)