Mock Object and Interface
- by tunl
I'm a newbie in Unit Test with Mock Object. I use EasyMock. I try to understand this example:
import java.io.IOException;
public interface ExchangeRate {
double getRate(String inputCurrency, String outputCurrency) throws IOException;
}
import java.io.IOException;
public class Currency {
private String units;
private long amount;
private int cents;
public Currency(double amount, String code) {
this.units = code;
setAmount(amount);
}
private void setAmount(double amount) {
this.amount = new Double(amount).longValue();
this.cents = (int) ((amount * 100.0) % 100);
}
public Currency toEuros(ExchangeRate converter) {
if ("EUR".equals(units)) return this;
else {
double input = amount + cents/100.0;
double rate;
try {
rate = converter.getRate(units, "EUR");
double output = input * rate;
return new Currency(output, "EUR");
} catch (IOException ex) {
return null;
}
}
}
public boolean equals(Object o) {
if (o instanceof Currency) {
Currency other = (Currency) o;
return this.units.equals(other.units)
&& this.amount == other.amount
&& this.cents == other.cents;
}
return false;
}
public String toString() {
return amount + "." + Math.abs(cents) + " " + units;
}
}
import junit.framework.TestCase;
import org.easymock.EasyMock;
import java.io.IOException;
public class CurrencyTest extends TestCase {
public void testToEuros() throws IOException {
Currency testObject = new Currency(2.50, "USD");
Currency expected = new Currency(3.75, "EUR");
ExchangeRate mock = EasyMock.createMock(ExchangeRate.class);
EasyMock.expect(mock.getRate("USD", "EUR")).andReturn(1.5);
EasyMock.replay(mock);
Currency actual = testObject.toEuros(mock);
assertEquals(expected, actual);
}
}
So, i wonder how to Currency use ExchangeRate in toEuros(..) method.
rate = converter.getRate(units, "EUR");
The behavior of getRate(..) method is not specified because ExchangeRate is an interface.
