Code
-----------
def say_hello(input_func):
    name = input_func()
    return "Hello " + name

def prompt_for_name():
    return raw_input("What is your name? ")

print say_hello(prompt_for_name)

Testing
-----------
def test_say_hello():
    output = say_hello(lambda: "Random Name")
    assert(output == "Hello Random Name")


OR

Code
-----------
def say_hello():
    if __name__ == '__main__':
        name = raw_input("What is your name? ")
    else:
        name = 'Random Name'
    return "Hello" + name

Testing
-----------
def test_say_hello():
    output = say_hello()
    assert(output == "Hello Random Name")