Java implementation of http://codekata.pragprog.com/2007/01/kata_eighteen_t.html using BDD

Dependencies.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

public class Dependencies {

	Map <String, Collection <String>> dependencyMap = new HashMap <String, Collection <String>>();

	public void addDirect( String target, String... deps ) {

		dependencyMap.put( target, Arrays.asList( deps ) );
	}

	public Collection <String> depsFor( String string ) {

		return depsFor( string, new ArrayList <String>() );
	}

	private Collection <String> depsFor( String target, ArrayList <String> transitive ) {

		Collection <String> directDependencies = directDependendcies( target );
		if ( directDependencies == null ) {
			return transitive;
		}
		for ( String dep : directDependencies ) {
			if ( !transitive.contains( dep ) ) {
				transitive.add( dep );
				transitive.addAll( depsFor( dep, transitive ) );
			}
		}
		return transitive;
	}

	private Collection <String> directDependendcies( String target ) {

		Collection <String> directDependencies = dependencyMap.get( target );
		return directDependencies;
	}

	public static boolean hasEquivalentDeps( Collection <String> left, Collection <String> right ) {

		if ( left.containsAll( right ) && right.containsAll( left ) ) {
			return true;
		}
		return false;
	}
}

WhenCalculatingDependencies.java

import java.util.Arrays;

import junit.framework.Assert;

import org.junit.Test;

public class WhenCalculatingDependencies {

	@Test
	public void shouldBeAbleToRememberFirstLevel() {

		Dependencies dependencies = new Dependencies();
		dependencies.addDirect( "A", "B", "C" );
		Assert.assertTrue( Dependencies.hasEquivalentDeps( Arrays.asList( "B", "C" ), dependencies.depsFor( "A" ) ) );
		dependencies.addDirect( "D", "C", "E" );
		Assert.assertTrue( Dependencies.hasEquivalentDeps( Arrays.asList( "C", "E" ), dependencies.depsFor( "D" ) ) );
	}

	@Test
	public void shouldNotCareAboutOrder() {

		Dependencies dependencies = new Dependencies();
		dependencies.addDirect( "A", "B", "C" );
		Assert.assertTrue( Dependencies.hasEquivalentDeps( Arrays.asList( "C", "B" ), dependencies.depsFor( "A" ) ) );
	}

	// case sensitivity

	@Test
	public void shouldBeAbleToCalculateTransitiveDependencies_2levels() throws Exception {

		Dependencies dependencies = new Dependencies();
		dependencies.addDirect( "A", "B", "C" );
		dependencies.addDirect( "B", "C", "E" );
		Assert.assertTrue( "B, C, E for A", Dependencies.hasEquivalentDeps( Arrays.asList( "B", "C", "E" ), dependencies.depsFor( "A" ) ) );
	}

	@Test
	public void shouldBeAbleToCalculateTransitiveDependencies_3levels() throws Exception {

		Dependencies dependencies = new Dependencies();
		dependencies.addDirect( "A", "B", "C" );
		dependencies.addDirect( "B", "C", "E" );
		dependencies.addDirect( "E", "G" );
		Assert.assertTrue( "B, C, E, G for A", Dependencies.hasEquivalentDeps( Arrays.asList( "B", "C", "E", "G" ), dependencies.depsFor( "A" ) ) );
	}

	@Test
	public void shouldBeAbleToCalculateTransitiveDependencies_Nlevels() throws Exception {

		Dependencies dependencies = new Dependencies();
		dependencies.addDirect( "A", "B", "C" );
		dependencies.addDirect( "B", "C", "E" );
		dependencies.addDirect( "C", "G" );
		dependencies.addDirect( "D", "A", "F" );
		dependencies.addDirect( "E", "F" );
		dependencies.addDirect( "F", "H" );
		Assert.assertTrue( Dependencies.hasEquivalentDeps( Arrays.asList( "B", "C", "E", "F", "G", "H" ), dependencies.depsFor( "A" ) ) );
		Assert.assertTrue( Dependencies.hasEquivalentDeps( Arrays.asList( "C", "E", "F", "G", "H" ), dependencies.depsFor( "B" ) ) );
		Assert.assertTrue( Dependencies.hasEquivalentDeps( Arrays.asList( "G" ), dependencies.depsFor( "C" ) ) );
		Assert.assertTrue( Dependencies.hasEquivalentDeps( Arrays.asList( "A", "B", "C", "E", "F", "G", "H" ), dependencies.depsFor( "D" ) ) );
		Assert.assertTrue( Dependencies.hasEquivalentDeps( Arrays.asList( "F", "H" ), dependencies.depsFor( "E" ) ) );
		Assert.assertTrue( Dependencies.hasEquivalentDeps( Arrays.asList( "H" ), dependencies.depsFor( "F" ) ) );
	}

	@Test
	public void shouldBeAbleToHandleCircularDependencies_level0() throws Exception {

		Dependencies dependencies = new Dependencies();
		dependencies.addDirect( "a", "a" );
		Assert.assertTrue( Dependencies.hasEquivalentDeps( Arrays.asList( "a" ), dependencies.depsFor( "a" ) ) );
	}

	@Test
	public void shouldBeAbleToHandleCircularDependencies_level1() throws Exception {

		Dependencies dependencies = new Dependencies();
		dependencies.addDirect( "a", "b" );
		dependencies.addDirect( "b", "a" );
		Assert.assertTrue( Dependencies.hasEquivalentDeps( Arrays.asList( "a", "b" ), dependencies.depsFor( "a" ) ) );
	}
}