3 simple test cases for Kruskal's algorithm for finding minimum spanning tree in a graph

MSTTest.java

import static org.junit.Assert.*;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Scanner;

import org.junit.Test;

public class MSTTest {

  public ArrayList<Graph> makeGraphList() {
		
		ArrayList<Graph> graphs = new ArrayList<Graph>();
		String text = "1 1 2 1#2 1 2 1 3 4 1#3 1 2 1 2 3 5 1 3 2#11 1 2 7 2 3 8 1 4 5 4 2 9 4 5 15 2 5 7 3 5 5 4 6 6 5 6 8 6 7 11 5 7 9";
		Scanner input = new Scanner(text);
		input.useDelimiter("#");
		String currentGraph;
		while (input.hasNext()) {
			currentGraph = input.next();
			graphs.add(new Graph(currentGraph));
		}
	
		input.close();
		return graphs;
	}
	
	@Test
	public void testSimpleTwoVertex() {
		ArrayList<Graph> graphs = makeGraphList();
		Collection<Edge> edgeList = MST.kruskals(graphs.get(0));
		assertNotNull(edgeList);
		assertEquals(1, edgeList.size());
		assertTrue(edgeList.contains(new Edge(new Vertex(1), new Vertex(2), 1)));
	}
	
	@Test
	public void testSimpleNotConnected() {
		ArrayList<Graph> graphs = makeGraphList();
		Collection<Edge> edgeList = MST.kruskals(graphs.get(1));
		assertNull(edgeList);
	}
	
	@Test
	public void testSimpleTriangle() {
		ArrayList<Graph> graphs = makeGraphList();
		Collection<Edge> edgeList = MST.kruskals(graphs.get(2));
		assertNotNull(edgeList);
		assertEquals(2, edgeList.size());
		assertTrue(edgeList.contains(new Edge(new Vertex(1), new Vertex(2), 1)));
		assertTrue(edgeList.contains(new Edge(new Vertex(1), new Vertex(3), 2)));
	}
}