Automated Testing: Parameterized Test

In the previous post, I introduced basic of Unit Testing.
Next I introduce parameterized testing.
Before explaning parameterized testing, let's define a simple service class which uses ExchangeRateApi calss.

package com.dukesoftware.exchangerate.service;

import java.util.HashMap;
import java.util.Map;

import com.dukesoftware.exchangerate.api.ExchangeRateApi;
import com.dukesoftware.exchangerate.api.Rate;

public class PriceCalculator {

    private final ExchangeRateApi api;
    private final Map<String, Rate> map = new HashMap<>();
    private final static double FEE_RATE = 0.05;

    public PriceCalculator(ExchangeRateApi api) {
        this.api = api;
    }
    
    public void initialize()
    {
    }
    
    public void shutdown()
    {
        this.map.clear();
    }

    public double calculatePrice(double price, String ccy1, String ccy2)
    {
        Rate rate = this.map.get(ccy1+":"+ccy2);
        if(rate == null)
        {
            // caching
            rate = this.api.getRate(ccy1, ccy2);
            this.map.put(ccy1+":"+ccy2, rate);
        }
    
        return rate.getValue() * (price * (1 + FEE_RATE));
    }
    
}

If you would like to test this PriceCalculator class by a bunch of currency combination, you can write test for each currency combination like...

package com.dukesoftware.exchangerate.service;

import junit.framework.Assert;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.dukesoftware.exchangerate.api.YahooExchangeRateApi;
import com.dukesoftware.exchangerate.service.PriceCalculator;

// TODO should use "Parameterized Test"
public class PriceCalculatorNotUsingParameterizedTest {

    private PriceCalculator service;
    
    @Before
    public void setUp()
    {
        // inject
        this.service = new PriceCalculator(new YahooExchangeRateApi());
        this.service.initialize();
    }
    
    @After
    public void tearDown()
    {
        this.service.shutdown();
    }
    
    @Test
    public void testCalculateJPYtoUSD()
    {
        double priceUSD = this.service.calculatePrice(10000, "JPY", "USD");
        
        Assert.assertEquals(100, priceUSD, 0.0001);
    }
    
    @Test
    public void testCalculatePHPtoUSD()
    {
        double priceUSD = this.service.calculatePrice(10000, "PHP", "USD");
        
        Assert.assertEquals(100, priceUSD, 0.0001);
    }
    
    @Test
    public void testCalculateHKDtoUSD()
    {
        double priceUSD = this.service.calculatePrice(10000, "HKD", "USD");
        
        Assert.assertEquals(100, priceUSD, 0.0001);
    }
    
    @Test
    public void testCalculateCHFtoUSD()
    {
        double priceUSD = this.service.calculatePrice(10000, "CHF", "USD");
        
        Assert.assertEquals(100, priceUSD, 0.0001);
    }

}

This is fine but, as you can see, a lot of part is duplicated.
In order to reduce this kind of duplication, we can use parameterized test.
You can write the parameterized test for above case by using @Parameters annotation.
Medthod annotated by @Parametrized should return parametrs formatted as Collection<Object[]&. Each Object[] indicates each test entry.
Please see below code.

package com.dukesoftware.exchangerate.service;

import java.util.Arrays;
import java.util.Collection;

import junit.framework.Assert;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;

import com.dukesoftware.exchangerate.api.YahooExchangeRateApi;
import com.dukesoftware.exchangerate.service.PriceCalculator;

@RunWith(Parameterized.class)
public class PriceCalculatorParameterizedTest {

    // write parameters here...
    @Parameters
    public static Collection<Object[]> parameters()
    {
        return Arrays.asList(
                new Object[][]{
                        { 100,   1.0395, "JPY", "USD"},
                        { 100,   2.4045, "PHP", "USD"},
                        { 10000, 1.05,   "IDR", "USD"}
                });
    }
    
    private PriceCalculator service;
    
    private final double price;
    private final double expectedPrice;
    private final String ccy1;
    private final String ccy2;
    
    public PriceCalculatorParameterizedTest(double price, double expectedPrice, String ccy1, String ccy2)
    {
        this.price = price;
        this.expectedPrice = expectedPrice;
        this.ccy1 = ccy1;
        this.ccy2 = ccy2;
    }
    
    @Before
    public void setUp()
    {
        // inject
        this.service = new PriceCalculator(new YahooExchangeRateApi());
        this.service.initialize();
    }
    
    @After
    public void tearDown()
    {
        this.service.shutdown();
    }
    
    @Test
    public void testCalculatePrice()
    {
        double actualPrice = this.service.calculatePrice(price, ccy1, ccy2);
        Assert.assertEquals(expectedPrice, actualPrice, 0.00001);
    }
}

After applying parameterized test, code readability is up, dupliaction is reduced, and Easy to add new combination of parameters :) Only disadvantedge of parameterized test is that each test doesn't have human readable name (still in JUnit4.8). I have seen someone enhance the JUnit library and make each test be able to have name.
(And I think JUnit team is working for this problem.)