Generic data type functionality implemented. All tests were refactored to reflect this, and some chromosome tests were rewritten with more rigorous assertions.

20 files changed, 182 insertions, 170 deletions

diff --git a/src/jcgp/CGP.java b/src/jcgp/CGP.java
index 6cf5429..d2be161 100644
--- a/src/jcgp/CGP.java
+++ b/src/jcgp/CGP.java
@@ -24,9 +24,13 @@ public final class CGP {
 	public CGP() {
 		initialise();
 
-		fitnessFunction.evaluate(population);
-
-		ea.evolve(population, mutator);
+		for (int i = 0; i < Parameters.getTotalGenerations(); i++) {
+			Parameters.setCurrentGeneration(i);
+			fitnessFunction.evaluate(population);
+			ea.evolve(population, mutator);
+		}
+		
+		
 	}
 
 	/**
@@ -51,7 +55,7 @@ public final class CGP {
 		Parameters.setMaxArity(functionSet.getMaxArity());
 		
 		// initialise fitness function and truth table
-		TruthTable.setTestCases(new TestCase(new int[] {2, 5, 4}, new int[] {1, 10, 15}));
+		TruthTable.setTestCases(new TestCase(new Object[] {2, 5, 4}, new Object[] {1, 10, 15}));
 		fitnessFunction = new TruthTableEvaluator();
 
 		// initialise EA
diff --git a/src/jcgp/Parameters.java b/src/jcgp/Parameters.java
index 2a417db..26eb61c 100644
--- a/src/jcgp/Parameters.java
+++ b/src/jcgp/Parameters.java
@@ -5,7 +5,7 @@ public class Parameters {
 	private static int rows, columns, inputs, outputs, levelsBack, 
 					   mutationRate, populationSize, totalGenerations,
 					   currentGeneration = 0, totalRuns, currentRun = 0,
-					   maxArity;
+					   maxArity, maxFitness;
 
 	public static int getRows() {
 		return rows;
@@ -58,6 +58,10 @@ public class Parameters {
 	public static int getMaxArity() {
 		return maxArity;
 	}
+	
+	public static int getMaxFitness() {
+		return maxFitness;
+	}
 
 	public static void setRows(int rows) {
 		Parameters.rows = rows;
@@ -111,4 +115,8 @@ public class Parameters {
 		Parameters.maxArity = maxArity;
 	}
 	
+	public static void setMaxFitness(int maxFitness) {
+		Parameters.maxFitness = maxFitness;
+	}
+	
 }
diff --git a/src/jcgp/ea/StandardEA.java b/src/jcgp/ea/StandardEA.java
index f401d9c..b34c421 100644
--- a/src/jcgp/ea/StandardEA.java
+++ b/src/jcgp/ea/StandardEA.java
@@ -6,8 +6,11 @@ import jcgp.population.Population;
 public class StandardEA implements EvolutionaryAlgorithm {
 
 	@Override
-	public void evolve(Population population, Mutator mutator) {		
+	public void evolve(Population population, Mutator mutator) {	
+		Chromosome select;
 		for (Chromosome chromosome : population) {
+			
+			
 			mutator.mutate(chromosome);
 		}
 	}
diff --git a/src/jcgp/fitness/TestCase.java b/src/jcgp/fitness/TestCase.java
index 95129c6..4c10de7 100644
--- a/src/jcgp/fitness/TestCase.java
+++ b/src/jcgp/fitness/TestCase.java
@@ -4,10 +4,10 @@ import jcgp.Parameters;
 
 public class TestCase {
 
-	private int[] inputs;
-	private int[] outputs;
+	private Object[] inputs;
+	private Object[] outputs;
 	
-	public TestCase(int[] inputs, int[] outputs) throws ParameterMismatchException {
+	public TestCase(Object[] inputs, Object[] outputs) throws ParameterMismatchException {
 		if (inputs.length == Parameters.getInputs()) {
 			this.inputs = inputs;
 		} else {
@@ -22,19 +22,19 @@ public class TestCase {
 		
 	}
 	
-	public int getInput(int index) {
+	public Object getInput(int index) {
 		return inputs[index];
 	}
 	
-	public int getOutput(int index) {
+	public Object getOutput(int index) {
 		return outputs[index];
 	}
 	
-	public int[] getInputs() {
+	public Object[] getInputs() {
 		return inputs;
 	}
 	
-	public int[] getOutputs() {
+	public Object[] getOutputs() {
 		return outputs;
 	}
 	
diff --git a/src/jcgp/fitness/TruthTableEvaluator.java b/src/jcgp/fitness/TruthTableEvaluator.java
index 987ea4c..4c26d60 100644
--- a/src/jcgp/fitness/TruthTableEvaluator.java
+++ b/src/jcgp/fitness/TruthTableEvaluator.java
@@ -19,6 +19,7 @@ public class TruthTableEvaluator implements FitnessFunction {
 					}
 				}
 				chromosome.setFitness(fitness);
+				System.out.println("Fitness: " + fitness);
 			}
 		}
 	}
diff --git a/src/jcgp/function/Addition.java b/src/jcgp/function/Addition.java
index 45a8d35..f40bc24 100644
--- a/src/jcgp/function/Addition.java
+++ b/src/jcgp/function/Addition.java
@@ -3,19 +3,23 @@ package jcgp.function;
 import jcgp.population.Connection;
 
 public class Addition extends Function {
+	
+	private int arity = 2;
 
 	@Override
-	public int run(Connection... connections) {
-		if (connections.length > 0) {
-			return connections[0].getValue() + connections[1].getValue();
+	public Object run(Connection... connections) {
+		if (connections.length < arity) {
+			throw new InvalidArgumentsException("Not enough connections were given.");
+		} else if (connections[0].getValue() instanceof Integer) {
+			return ((Integer) connections[0].getValue()) + ((Integer) connections[1].getValue());
 		} else {
-			throw new InsufficientArgumentsException();
+			throw new InvalidArgumentsException("Wrong data type, this function takes Integer.");
 		}
 	}
 
 	@Override
 	public int getArity() {
-		return 2;
+		return arity;
 	}
 
 }
diff --git a/src/jcgp/function/Function.java b/src/jcgp/function/Function.java
index 4900c68..118131a 100644
--- a/src/jcgp/function/Function.java
+++ b/src/jcgp/function/Function.java
@@ -4,8 +4,8 @@ import jcgp.population.Connection;
 import jcgp.population.InsufficientConnectionsException;
 
 public abstract class Function {
-	
-	public abstract int run(Connection ... connections) throws InsufficientConnectionsException;
+		
+	public abstract Object run(Connection ... connections) throws InsufficientConnectionsException;
 	
 	public abstract int getArity();
 	
diff --git a/src/jcgp/function/InsufficientArgumentsException.java b/src/jcgp/function/InsufficientArgumentsException.java
deleted file mode 100644
index a591b20..0000000
--- a/src/jcgp/function/InsufficientArgumentsException.java
+++ /dev/null
@@ -1,10 +0,0 @@
-package jcgp.function;
-
-public class InsufficientArgumentsException extends RuntimeException {
-
-	/**
-	 * 
-	 */
-	private static final long serialVersionUID = 2675108124600817777L;
-
-}
diff --git a/src/jcgp/function/InvalidArgumentsException.java b/src/jcgp/function/InvalidArgumentsException.java
new file mode 100644
index 0000000..cf55937
--- /dev/null
+++ b/src/jcgp/function/InvalidArgumentsException.java
@@ -0,0 +1,20 @@
+package jcgp.function;
+
+public class InvalidArgumentsException extends RuntimeException {
+
+	/**
+	 * 
+	 */
+	private static final long serialVersionUID = 2675108124600817777L;
+	private String reason;
+	
+	public InvalidArgumentsException(String reason) {
+		super();
+		this.reason = reason;
+	}
+	
+	public String getReason() {
+		return reason;
+	}
+
+}
diff --git a/src/jcgp/function/Subtraction.java b/src/jcgp/function/Subtraction.java
index 8f107b1..d785614 100644
--- a/src/jcgp/function/Subtraction.java
+++ b/src/jcgp/function/Subtraction.java
@@ -4,18 +4,22 @@ import jcgp.population.Connection;
 
 public class Subtraction extends Function {
 
+	private int arity = 2;
+
 	@Override
-	public int run(Connection... connections) {
-		if (connections.length > 1) {
-			return connections[0].getValue() - connections[1].getValue();
+	public Object run(Connection... connections) {
+		if (connections.length < arity) {
+			throw new InvalidArgumentsException("Not enough connections were given.");
+		} else if (connections[0].getValue() instanceof Integer) {
+			return ((Integer) connections[0].getValue()) - ((Integer) connections[1].getValue());
 		} else {
-			throw new InsufficientArgumentsException();
+			throw new InvalidArgumentsException("Wrong data type, this function takes Integer.");
 		}
 	}
 
 	@Override
 	public int getArity() {
-		return 2;
+		return arity;
 	}
 
 }
diff --git a/src/jcgp/population/Chromosome.java b/src/jcgp/population/Chromosome.java
index f61b780..12a8978 100644
--- a/src/jcgp/population/Chromosome.java
+++ b/src/jcgp/population/Chromosome.java
@@ -158,7 +158,7 @@ public class Chromosome {
 	 * @param values
 	 * @throws ParameterMismatchException
 	 */
-	public void setInputs(int ... values) throws ParameterMismatchException {
+	public void setInputs(Object ... values) throws ParameterMismatchException {
 		// if the values provided don't match the specified number of inputs, the user should be warned
 		if (values.length == inputs.length) {
 			// set inputs for evaluation
diff --git a/src/jcgp/population/Connection.java b/src/jcgp/population/Connection.java
index 3312de3..ff11d7c 100644
--- a/src/jcgp/population/Connection.java
+++ b/src/jcgp/population/Connection.java
@@ -2,6 +2,6 @@ package jcgp.population;
 
 public interface Connection {
 
-	public int getValue();
+	public Object getValue();
 
 }
diff --git a/src/jcgp/population/Input.java b/src/jcgp/population/Input.java
index ee008ce..2154dd9 100644
--- a/src/jcgp/population/Input.java
+++ b/src/jcgp/population/Input.java
@@ -2,18 +2,19 @@ package jcgp.population;
 
 public class Input implements Connection {
 	
-	private int value = 0, index;
+	private Object value = 0;
+	private int index;
 	
 	public Input(int index) {
 		this.index = index;
 	}
 	
-	public void setValue(int newValue) {
+	public void setValue(Object newValue) {
 		value = newValue;
 	}
 
 	@Override
-	public int getValue() {
+	public Object getValue() {
 		return value;
 	}
 
diff --git a/src/jcgp/population/Node.java b/src/jcgp/population/Node.java
index b2e29df..e58c1a4 100644
--- a/src/jcgp/population/Node.java
+++ b/src/jcgp/population/Node.java
@@ -23,7 +23,7 @@ public class Node implements MutableElement, Connection {
 	}
 
 	@Override
-	public int getValue() {
+	public Object getValue() {
 		return function.run(Arrays.copyOfRange(connections, 0, function.getArity()));
 	}
 
diff --git a/src/jcgp/population/Output.java b/src/jcgp/population/Output.java
index f0bcbbf..dae7278 100644
--- a/src/jcgp/population/Output.java
+++ b/src/jcgp/population/Output.java
@@ -13,7 +13,7 @@ public class Output implements MutableElement {
 		this.index = index;
 	}
 
-	public int calculate() {
+	public Object calculate() {
 		return source.getValue();
 	}
 
diff --git a/src/jcgp/tests/ChromosomeTests.java b/src/jcgp/tests/ChromosomeTests.java
index d2407a6..8092d60 100644
--- a/src/jcgp/tests/ChromosomeTests.java
+++ b/src/jcgp/tests/ChromosomeTests.java
@@ -6,7 +6,6 @@ import java.util.Random;
 
 import jcgp.Parameters;
 import jcgp.Utilities;
-import jcgp.fitness.ParameterMismatchException;
 import jcgp.function.Addition;
 import jcgp.function.FunctionSet;
 import jcgp.function.Subtraction;
@@ -31,8 +30,7 @@ import org.junit.Test;
  *  - It should be able to return a random connection.
  *  - It should contain a freely modifiable fitness value.
  *  - For truth table evaluations, it should be able to have its inputs set.
- *  - For truth table evaluations, the output should return a value according to what
- *    it is set to.
+ *  - For truth table evaluations, the output should return a value according to the inputs.
  *  - It should feature a clone constructor, which creates a deep copy of a 
  *    specified Chromosome object.
  *  - It should be able to return a list of active nodes.
@@ -40,7 +38,6 @@ import org.junit.Test;
  *    to it.
  *  - Same as above, but only looking at the active portion of a chromosome.
  *  
- *  TODO: bashing (strange value ranges, etc)
  *  
  *  WARNING: changing parameters may cause the tests to incorrectly fail!
  * 
@@ -60,19 +57,19 @@ public class ChromosomeTests {
 		Utilities.setResources(new Random(1234), functionSet);
 
 		// initialise parameters
-		Parameters.setColumns(30);
-		Parameters.setRows(20);
-		Parameters.setInputs(2);
-		Parameters.setOutputs(4);
-		Parameters.setLevelsBack(1);
 		Parameters.setMutationRate(10);
-		Parameters.setTotalGenerations(100);
+		Parameters.setTotalGenerations(10);
 		Parameters.setTotalRuns(5);
 		Parameters.setMaxArity(functionSet.getMaxArity());
 	}
 
 	@Before
 	public void setUp() throws Exception {
+		Parameters.setColumns(10);
+		Parameters.setRows(2);
+		Parameters.setInputs(2);
+		Parameters.setOutputs(4);
+		Parameters.setLevelsBack(10);
 		chromosome = new Chromosome();
 	}
 
@@ -81,7 +78,6 @@ public class ChromosomeTests {
 	 */
 	@Test
 	public void cloneTest() {
-		int[] testInputs;
 		// create a clone, check to see if it really is a clone
 		Chromosome clone = new Chromosome(chromosome);
 
@@ -146,29 +142,26 @@ public class ChromosomeTests {
 			}
 		}
 
-		// set input values
-		testInputs = new int[Parameters.getInputs()];
-		for (int i = 0; i < Parameters.getInputs(); i++) {
-			testInputs[i] = (i + 1) * 2 - 3;
-		}
-		chromosome.setInputs(testInputs);
-		clone.setInputs(testInputs);
+		// check cloning given a known topology
+		chromosome = createKnownConfiguration();
+		clone = new Chromosome(chromosome);
+		
+		Integer[] testInputs = new Integer[] {5, 8, 4};
+		chromosome.setInputs((Object[]) testInputs);
+		clone.setInputs((Object[]) testInputs);
 
 		// check that both chromosomes have the same outputs
 		for (int i = 0; i < Parameters.getOutputs(); i++) {
-			assertTrue("Incorrect output returned.", chromosome.getOutput(i).calculate() == 
-					clone.getOutput(i).calculate());
+			assertTrue("Incorrect output returned", ((Integer) chromosome.getOutput(i).calculate()) == ((Integer) clone.getOutput(i).calculate()));
 		}
 
-		// mutate an active node in clone, check that the same node in chromosome produces a different output
-		// NOTE: given a small grid this mutation may actually pick the same connection (causing no effective change) and therefore the test would fail.
-		Node node = clone.getActiveNodes().get(Utilities.getRandomInt(clone.getActiveNodes().size()));
-		node.setConnection(clone.getRandomConnection(node.getColumn()));
+		// mutate an output in clone, check that the same node in chromosome produces a different output
+		clone.getOutput(1).setConnection(clone.getInput(2));
 
-		assertTrue("Mutation affected both nodes in both chromosomes.", node.getValue() != chromosome.getNode(node.getRow(), node.getColumn()).getValue());
+		assertTrue("Mutation affected nodes in both chromosomes.",
+				clone.getOutput(1).calculate() != chromosome.getOutput(1).calculate());
 
 	}
-
 	/**
 	 * 
 	 */
@@ -217,7 +210,6 @@ public class ChromosomeTests {
 
 		System.out.println(connectionOutOfRange + " nodes that disrespected levels back were picked.");
 	}
-
 	/**
 	 * 
 	 */
@@ -249,27 +241,28 @@ public class ChromosomeTests {
 	 */
 	@Test
 	public void getOutputsTest() {
-		// connect outputs to inputs, check that calculated outputs return input values
-		for (int i = 0; i < Parameters.getOutputs(); i++) {
-			chromosome.getOutput(i).setConnection(chromosome.getInput(i % Parameters.getInputs()));
-			assertTrue("Incorrect output returned.", chromosome.getOutput(i).calculate() == 
-					chromosome.getInput(i % Parameters.getInputs()).getValue());
-		}
+		chromosome = createKnownConfiguration();
+
+		chromosome.setInputs(5, 8, 4);
+
+		// with this configuration, the outputs should be 13 and 25.
+		assertTrue("Incorrect output returned.", (Integer) chromosome.getOutput(0).calculate() == 13);
+		assertTrue("Incorrect output returned.", (Integer) chromosome.getOutput(1).calculate() == 25);
 	}
 
 	/**
-	 * @throws ParameterMismatchException
+	 * 
 	 */
 	@Test
-	public void setInputTest() throws ParameterMismatchException {
+	public void setInputTest() {
 		// set input values, check that acquired values are correct
-		int[] testInputs = new int[Parameters.getInputs()];
+		Integer[] testInputs = new Integer[Parameters.getInputs()];
 		for (int i = 0; i < Parameters.getInputs(); i++) {
 			testInputs[i] = i * 2 - 3;
 		}
-		chromosome.setInputs(testInputs);
+		chromosome.setInputs((Object[]) testInputs);
 		for (int i = 0; i < Parameters.getInputs(); i++) {
-			assertTrue("Incorrect input returned.", chromosome.getInput(i).getValue() == i * 2 - 3);
+			assertTrue("Incorrect input returned.", ((Integer) chromosome.getInput(i).getValue()) == i * 2 - 3);
 		}
 	}
 
@@ -294,20 +287,15 @@ public class ChromosomeTests {
 	public void activeNodeTest() {
 		// active node detection happens recursively, the user only calls a single method
 		// set connections to a known configuration
-		for (int i = 0; i < Parameters.getOutputs(); i++) {
-			chromosome.getOutput(i).setConnection(chromosome.getNode(0, 0));
-		}
-
-		chromosome.getNode(0, 0).setConnection(chromosome.getInput(0));
-
-		assertTrue("Active node not in list.", chromosome.getActiveNodes().contains(chromosome.getNode(0, 0)));
-
-		// change outputs, print list
-		chromosome.getOutput(0).setConnection(chromosome.getNode(0, Parameters.getColumns() - 1));
-
-		System.out.println("Active connections: " + chromosome.getActiveNodes().toString() + "\n");
+		chromosome = createKnownConfiguration();
+		
+		assertTrue("Active node missing from list.", chromosome.getActiveNodes().contains(chromosome.getNode(0, 0)));
+		assertTrue("Active node missing from list.", chromosome.getActiveNodes().contains(chromosome.getNode(1, 1)));
+		assertTrue("Active node missing from list.", chromosome.getActiveNodes().contains(chromosome.getNode(1, 2)));
+		
+		assertTrue("List has the wrong number of nodes.", chromosome.getActiveNodes().size() == 3);
 	}
-	
+
 	/**
 	 * 
 	 */
@@ -317,12 +305,12 @@ public class ChromosomeTests {
 		Chromosome c = new Chromosome(chromosome);
 		assertTrue("Active nodes did not match.", chromosome.compareActiveTo(c));
 		assertTrue("Symmetry not obeyed.", c.compareActiveTo(chromosome));
-		
+
 		// create a new random chromosome, this time they should not match
 		c = new Chromosome();
 		assertTrue("Active nodes did match.", !chromosome.compareActiveTo(c));
 	}
-	
+
 	/**
 	 * 
 	 */
@@ -332,9 +320,37 @@ public class ChromosomeTests {
 		Chromosome c = new Chromosome(chromosome);
 		assertTrue("Chromosomes did not match.", chromosome.compareTo(c));
 		assertTrue("Symmetry not obeyed.", c.compareTo(chromosome));
-		
+
 		// create a new random chromosome, this time they should not match
 		c = new Chromosome();
 		assertTrue("Chromosomes did match.", !chromosome.compareTo(c));
 	}
+	/**
+	 * Utility for creating a chromosome of known configuration.
+	 * Topology is 3x3, with 3 inputs and 2 outputs.
+	 * Given inputs 5, 8 and 4 outputs should be 13 and 25.
+	 * 
+	 * Active nodes (r, c): [0, 0], [1, 1], [1, 2]
+	 * 
+	 * @return the configured chromosome
+	 */
+	private Chromosome createKnownConfiguration() {
+		// with a small topology, build a chromosome of known connections and check outputs
+		Parameters.setColumns(3);
+		Parameters.setRows(3);
+		Parameters.setInputs(3);
+		Parameters.setOutputs(2);
+		Parameters.setLevelsBack(3);
+
+		Chromosome c = new Chromosome();
+
+		c.getNode(0, 0).initialise(Utilities.getFunction(0), c.getInput(0), c.getInput(1));
+		c.getNode(1, 1).initialise(Utilities.getFunction(0), c.getNode(0, 0), c.getInput(1));
+		c.getNode(1, 2).initialise(Utilities.getFunction(0), c.getNode(1, 1), c.getInput(2));
+
+		c.getOutput(0).setConnection(c.getNode(0, 0));
+		c.getOutput(1).setConnection(c.getNode(1, 2));
+
+		return c;
+	}
 }
diff --git a/src/jcgp/tests/InputTests.java b/src/jcgp/tests/InputTests.java
index 3803990..51d58d2 100644
--- a/src/jcgp/tests/InputTests.java
+++ b/src/jcgp/tests/InputTests.java
@@ -35,7 +35,7 @@ public class InputTests {
 		// assign a value to input, check that the returned value is correct
 		input.setValue(inputValue);
 
-		assertTrue("Incorrect value returned.", input.getValue() == inputValue);
+		assertTrue("Incorrect value returned.", ((Integer) input.getValue()) == inputValue);
 	}
 
 	@Test
diff --git a/src/jcgp/tests/NodeTests.java b/src/jcgp/tests/NodeTests.java
index 5b378d2..9ea6769 100644
--- a/src/jcgp/tests/NodeTests.java
+++ b/src/jcgp/tests/NodeTests.java
@@ -6,11 +6,11 @@ import java.util.Random;
 
 import jcgp.Parameters;
 import jcgp.Utilities;
+import jcgp.function.Addition;
 import jcgp.function.Function;
-import jcgp.function.InsufficientArgumentsException;
+import jcgp.function.Subtraction;
 import jcgp.population.Chromosome;
 import jcgp.population.Connection;
-import jcgp.population.InsufficientConnectionsException;
 import jcgp.population.Node;
 
 import org.junit.Before;
@@ -63,44 +63,25 @@ public class NodeTests {
 	public void setUp() throws Exception {
 		node = new Node(chromosome, 0, 0);
 		// make node with anonymous addition function and hard-coded value connections
-		node.initialise(new Function() {
-			private int arity = 2;
+		node.initialise(new Addition(),
+				new Connection[]{new Connection() {
 
-			@Override
-			public int run(Connection... connections) {
-
-				// add together the first n inputs if they exist, else throw exception
-				if (connections.length >= arity) {
-					return connections[0].getValue() + connections[1].getValue();
-				} else {
-					throw new InsufficientArgumentsException();
-				}
-			}
+					@Override
+					public Object getValue() {
+						// hardcode a value
+						return arg1;
+					}
 
-			@Override
-			public int getArity() {
-				// addition with arity 2
-				return arity;
-			}
+				},
+				new Connection() {
 
-		}, new Connection[]{new Connection() {
+					@Override
+					public Object getValue() {
+						// hardcode a value
+						return arg2;
+					}
 
-			@Override
-			public int getValue() {
-				// hardcode a value
-				return arg1;
-			}
-
-		},
-		new Connection() {
-
-			@Override
-			public int getValue() {
-				// hardcode a value
-				return arg2;
-			}
-
-		}});
+				}});
 	}
 
 	@Test
@@ -115,8 +96,7 @@ public class NodeTests {
 		Function f = new Function() {
 
 			@Override
-			public int run(Connection... connections)
-					throws InsufficientConnectionsException {
+			public Object run(Connection... connections) {
 				// blank
 				return 0;
 			}
@@ -133,36 +113,19 @@ public class NodeTests {
 		// check that the function returned by the node is f
 		assertTrue("Incorrect function returned.", node.getFunction() == f);
 		// check that it outputs 0 as it should
-		assertTrue("Incorrect function output.", node.getValue() == 0);
+		assertTrue("Incorrect function output.", ((Integer) node.getValue()) == 0);
 	}
 
 	@Test
 	public void evaluationTest() {
 		// check that addition is working
-		assertTrue("Node did not return expected value (sum of arguments).", node.getValue() == arg1 + arg2);
+		assertTrue("Node did not return expected value (sum of arguments). Output was: " + ((int) node.getValue()), 
+				((int) node.getValue()) == arg1 + arg2);
 
 		// put in a different function, check the output has changed appropriately
-		node.setFunction(new Function() {
+		node.setFunction(new Subtraction());
 
-			private int arity = 2;
-
-			@Override
-			public int run(Connection... connections) throws InsufficientConnectionsException {
-				// add together the first n inputs if they exist, else throw exception
-				if (connections.length >= arity) {
-					return connections[0].getValue() - connections[1].getValue();
-				} else {
-					throw new InsufficientArgumentsException();
-				}
-			}
-
-			@Override
-			public int getArity() {
-				return arity;
-			}
-		});
-
-		assertTrue("Node did not return expected value (difference of arguments).", node.getValue() == arg1 - arg2);
+		assertTrue("Node did not return expected value (difference of arguments).", ((Integer) node.getValue()) == arg1 - arg2);
 
 	}
 
@@ -173,7 +136,7 @@ public class NodeTests {
 		conn0 = new Connection() {
 
 			@Override
-			public int getValue() {
+			public Object getValue() {
 				// blank
 				return 0;
 			}
@@ -182,31 +145,31 @@ public class NodeTests {
 		conn1 = new Connection() {
 
 			@Override
-			public int getValue() {
+			public Object getValue() {
 				// blank
 				return 0;
 			}
 
 		};
 		node.initialise(null, conn0, conn1);
-		
+
 		assertTrue("Connection 0 is incorrect.", node.getConnection(0) == conn0);
 		assertTrue("Connection 1 is incorrect.", node.getConnection(1) == conn1);
-		
+
 		// make yet another connection, set it randomly, check that it is one of the node's connections
 		conn2 = new Connection() {
 
 			@Override
-			public int getValue() {
+			public Object getValue() {
 				// blank
 				return 0;
 			}
 		};
 		node.setConnection(conn2);
-		
+
 		assertTrue("Connection was not found in node.", node.getConnection(0) == conn2 || node.getConnection(1) == conn2);
-		
+
 	}
-	
+
 
 }
diff --git a/src/jcgp/tests/OutputTests.java b/src/jcgp/tests/OutputTests.java
index 04eac7f..c877c03 100644
--- a/src/jcgp/tests/OutputTests.java
+++ b/src/jcgp/tests/OutputTests.java
@@ -64,13 +64,13 @@ public class OutputTests {
 		output.setConnection(new Connection() {
 
 			@Override
-			public int getValue() {
+			public Object getValue() {
 				// test value
 				return outputValue;
 			}
 		});
 
-		assertTrue("Incorrect evaluation.", output.calculate() == outputValue);
+		assertTrue("Incorrect evaluation.", ((Integer) output.calculate()) == outputValue);
 	}
 
 	@Test
@@ -79,7 +79,7 @@ public class OutputTests {
 		Connection newConn = new Connection() {
 
 			@Override
-			public int getValue() {
+			public Object getValue() {
 				// blank
 				return 0;
 			}
diff --git a/src/jcgp/tests/PopulationTests.java b/src/jcgp/tests/PopulationTests.java
index a8f55a2..bb8fece 100644
--- a/src/jcgp/tests/PopulationTests.java
+++ b/src/jcgp/tests/PopulationTests.java
@@ -170,7 +170,5 @@ public class PopulationTests {
 				}
 			}
 		}
-
 	}
-
 }