MATLAB Programming Fundamentals - MathWorks

function price = lookupPrice(ticker,date)

% This method assumes you have installed and configured the

% Bloomberg software.

conn = blp;

data = history(conn,ticker,'LAST_PRICE',date-1,date);

price = data(end);

close(conn)

end

end

end

In this example, assume that the broker component has not been developed yet. Once it is

implemented, it will have a buy method that accepts a ticker symbol and a specified

number of shares to buy, and returns a status code. The mock for the broker component

uses an implicit interface, and does not derive from a superclass.

Component Under Test

In a file trader.m in your current working folder, create a simple day trading algorithm.

The trader function accepts as inputs a data service object that looks up the price of the

stock, a broker object that defines how the stock is bought, a ticker symbol, and a number

of shares to purchase. If the price from yesterday is less than the price two days ago,

instruct the broker to buy the specified number of shares.

function trader(dataService,broker,ticker,numShares)

yesterday = datetime('yesterday');

priceYesterday = dataService.lookupPrice(ticker,yesterday);

price2DaysAgo = dataService.lookupPrice(ticker,yesterday-days(1));

if priceYesterday < price2DaysAgo

broker.buy(ticker,numShares);

end

end

Mock Objects and Behavior Objects

The mock object is an implementation of the abstract methods and properties of the

interface specified by a superclass. You can also construct a mock without a superclass, in

which case the mock has an implicit interface. The mock object carries out the actions for

the component under test, such as calling a method or accessing a property.

33 Unit Testing