XpUg Coding Dojo: KataYahtzee in Ocp way

Xpug Coding Dojo: The OCP Kata

Randori

Costraints

The OCP Kata http://matteo.vaccari.name/blog/archives/293

0. Write the first failing test.

Then write a factory that returns an object, or an aggregate of objects, that make the test pass.

The factory should be limited to creating objects and linking them together. No conditionals allowed.

1. Write the next failing test.

2. Can you make it pass by changing the factory and/or creating a new class and nothing else?

If yes, great! Go back to 1.

If not, refactor until you can.

The refactoring should bring the system to a state where it’s possible to implement the next test just by changing the aggregate of objects that is returned by the factory.

Be careful not to implement new functionality; the current test should still fail.

An example

package xpug; import junit.framework.Assert; import org.junit.Test; public class AFizzbuzzer { @Test public void shouldReturnSameNumberForPlainNumber() { Fizzbuzzer fizzbuzzer = FizzbuzzerFactory.create(); Assert.assertEquals("1", fizzbuzzer.say(1)); Assert.assertEquals("2", fizzbuzzer.say(2)); } }

package xpug; public class FizzbuzzerFactory { public static Fizzbuzzer create() { return new Fizzbuzzer(); } }

package xpug; public class Fizzbuzzer { public String say(int digit){ return String.valueOf(digit); } }

@Test public void shouldReturnFizzForMultipleOfThree(){ Fizzbuzzer fizzbuzzer = FizzbuzzerFactory.create(); Assert.assertEquals("Fizz", fizzbuzzer.say(3)); Assert.assertEquals("Fizz", fizzbuzzer.say(6)); Assert.assertEquals("Fizz", fizzbuzzer.say(9)); }

package xpug; public interface Counter { public boolean canHandle(int digit); public String say(int digit); }

package xpug; public class Echo implements Counter { @Override public boolean canHandle(int digit) { return true; } @Override public String say(int digit) { return String.valueOf(digit); } }

package xpug; import java.util.List; public class Fizzbuzzer { private List<? extends Counter> counters; public Fizzbuzzer(List<? extends Counter> counters) { this.counters = counters; } public String say(int digit) { for (Counter counter : counters) if (counter.canHandle(digit)) return counter.say(digit); return ""; } }

package xpug; import java.util.Arrays; public class FizzbuzzerFactory { public static Fizzbuzzer create() { return new Fizzbuzzer(Arrays.asList( new Echo())); } }

@Test public void shouldReturnFizzForMultipleOfThree(){ Fizzbuzzer fizzbuzzer = FizzbuzzerFactory.create(); Assert.assertEquals("Fizz", fizzbuzzer.say(3)); Assert.assertEquals("Fizz", fizzbuzzer.say(6)); Assert.assertEquals("Fizz", fizzbuzzer.say(9)); }

package xpug; public class Fizz implements Counter { @Override public boolean canHandle(int digit) { return digit % 3 == 0; } @Override public String say(int digit) { return "Fizz"; } }

package xpug; import java.util.Arrays; public class FizzbuzzerFactory { public static Fizzbuzzer create() { return new Fizzbuzzer(Arrays.asList( new Fizz(), new Echo())); } }

... ... ... ... ... ... ...

package xpug; import java.util.Arrays; public class FizzbuzzerFactory { public static Fizzbuzzer create() { return new Fizzbuzzer(Arrays.asList( new Fizzbuzz(), new Buzz(), new Fizz(), new Echo())); } }

KataYahtzee

Let’s start!

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XpUg Coding Dojo: KataYahtzee in Ocp way

by giordano scalzo on Jan 29, 2010

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XpUg Coding Dojo: KataYahtzee in Ocp way — Presentation Transcript