def evaluate_increment(lower_boundary, upper_boundary):
    lower_boundary_height = evaluate_function(lower_boundary)
    upper_boundary_height = evaluate_function(upper_boundary)
    print ('lower_value = ', lower_boundary_height)
    print ('upper_value = ', upper_boundary_height)
    increment_area = ((lower_boundary_height + upper_boundary_height)/2) * (upper_boundary - lower_boundary)
    return increment_area
def evaluate_increment(lower_boundary, upper_boundary):
    lower_boundary_height = evaluate_function(lower_boundary)
    upper_boundary_height = evaluate_function(upper_boundary)
    print('lower_value = ', lower_boundary_height)
    print('upper_value = ', upper_boundary_height)
    increment_area = ((lower_boundary_height + upper_boundary_height) /
                      2) * (upper_boundary - lower_boundary)
    return increment_area
def test_evaluate_function():
    """
    the function should evaluate the expression
    """
    assert evaluate_function(0) == 3

    assert evaluate_function(3) == 12

    assert evaluate_function(5) == 28
def test_evaluate_function():
    """
    the function should evaluate the expression
    """
    assert evaluate_function(0) == 3

    assert evaluate_function(3) == 12

    assert evaluate_function(5) == 28