Stack pers in py

#Stack class, unit tests below it (courtesy of Blake!) (to be put in their own file!)
class Stack:
    def __init__(self):
        """Cannot be initialized with data!"""
        self.m_data = []

    def size(self):
        """Returns the size of the stack"""
        return len(self.m_data)

    def is_empty(self):
        """Returns a bool showing whether or not the stack is empty"""
        if self.size() == 0:
            result = True
        else:
            result = False
        return result

    def push(self,input):
        """Pushes the next element onto the stack"""
        self.m_data.append(input)

    def peek(self):
        """Returns the last item on the stack"""
        return self.m_data[self.size()-1]

    def pop(self):
        """Returns the last item on the stack, and removes it from the stack"""
        return self.m_data.pop()


#unit tests (made by Blake)
import unittest
import Stack

class stackOperationMethods(unittest.TestCase):

    def test_returns_empty_stack(self):
        self.assertIsInstance(Stack.Stack(), Stack.Stack)

    def test_push_item(self):
        newStack = Stack.Stack()
        prePushSize = newStack.size()
        newStack.push(1)
        self.assertTrue(newStack.size() == prePushSize + 1)

    def test_pop(self):
        newStack = Stack.Stack()
        prePopSize = newStack.size()
        newStack.push(1)
        self.assertTrue(newStack.pop() == 1)
        self.assertTrue(newStack.size() == 0)

    def test_peek(self):
        newStack = Stack.Stack()
        prePeekSize = newStack.size()
        newStack.push(1)
        self.assertTrue(newStack.peek() == 1)
        self.assertTrue(newStack.size() == 1)

    def test_is_empty(self):
        newStack = Stack.Stack()
        self.assertTrue(newStack.is_empty() == True)
        newStack.push(1)
        self.assertFalse(newStack.is_empty() == True)
        newStack.pop()
        self.assertTrue(newStack.is_empty()== True)

    def test_size(self):
        newStack = Stack.Stack()
        for i in range(1,10):
            newStack.push(i)
        self.assertTrue(newStack.size() == 9)


if __name__ == "__main__":
    unittest.main()