How to test collections in Junit (Java)

Question

I need to implement a sparse graph and do some junit tests on it.

This is my graph class:

package graphs;
import java.util.Collection;
import java.util.HashMap;
public class SparseGraph<V, E> implements Graph<V, E> {
    HashMap<V, HashMap<V, E>> node;
    public SparseGraph() {
        node = new HashMap<>();
    }
    @Override
    public boolean addVertex(V vertex) {
        if (hasVertex(vertex)) {
            return false;
        }
        else {
            node.put(vertex, new HashMap());
        }
        return true;
    }
    @Override
    public boolean addEdge(V vertex1, V vertex2, E data) {
        if (!hasVertex(vertex1) || !hasVertex(vertex2)) {
            return false;
        }
        if (hasEdge(vertex1, vertex2) && getData(vertex1, vertex2).equals(data)) {
            return false;
        }
        else if (hasEdge(vertex1, vertex2) && !getData(vertex1, vertex2).equals(data)) {
            node.get(vertex1).put(vertex2, data);
            return true;
        }
        else {
            (node.get(vertex1)).put(vertex2, data);
        }
        return true;
    }
    @Override
    public boolean hasVertex(V vertex) {
        if (vertex == null) return false;
        return (node.containsKey(vertex));
    }
    @Override
    public boolean hasEdge(V vertex1, V vertex2) {
        if (!hasVertex(vertex1) || !hasVertex(vertex2)) return false;
        if (node.get(vertex1).containsKey(vertex2)) {
            return true;
        }
        return false;
    }
    @Override
    public E getData(V vertex1, V vertex2) {
        if (!hasVertex(vertex1) || !hasVertex(vertex2)) return null;
        return node.get(vertex1).get(vertex2);
    }
    @Override
    public Collection<V> getVertices() {
        return node.keySet();
    }
    @Override
    public Collection<V> getNeighbors(V vertex) {
        if (!hasVertex(vertex))
            return null;
        else
            return node.get(vertex).keySet();
    }
}// end class

and this is my test:

public void testGetVertices() {
    SparseGraph instance = new SparseGraph();
    instance.addVertex("A");
    instance.addVertex("B");
    instance.addVertex("C");
    instance.addVertex("D");
    instance.addVertex("E");
    //assertEquals("[D, E, A, B, C]",instance.getVertices());
}

My question is, how can I create a test that checks if all vertices are present in my Collection?

I tried comparing a string with the keySet, but the error was that is expected a string but method assertEquals gets a keySet.

Answer 1

There are many ways of testing this. The most basic one is to do a contains for each element but JUnit has more elegant ways. You can use assertThat() together with the Hamcrest

assertThat(instance.getVertices(), containsInAnyOrder("A", "B", "C", "D", "E"));

use following imports:

import static org.junit.Assert.assertThat;
import static org.hamcrest.CoreMatchers.hasItems;
import static org.hamcrest.Matchers.containsInAnyOrder;

Answer 2

I'd iterate over the graph and check to see if each one appears in a List of expected values.

Answer 3

A JUnit-Test with plain Java would look like this:

assertEquals(5, instance.getVertices().size());
assertTrue(instance.getVertices().hasVertex("A"));
assertTrue(instance.getVertices().hasVertex("B"));
assertTrue(instance.getVertices().hasVertex("C"));
assertTrue(instance.getVertices().hasVertex("D"));
assertTrue(instance.getVertices().hasVertex("E"));