Add tests, fix removeEdge bug in MatrixGraphs (#5968)

src/test/java/com/thealgorithms/datastructures/graphs/MatrixGraphsTest.java

@@ -0,0 +1,140 @@
+package com.thealgorithms.datastructures.graphs;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+class MatrixGraphsTest {
+
+    @Test
+    void testGraphConstruction() {
+        AdjacencyMatrixGraph graph = new AdjacencyMatrixGraph(5);
+        assertEquals(5, graph.numberOfVertices());
+        assertEquals(0, graph.numberOfEdges());
+    }
+
+    @Test
+    void testAddEdge() {
+        AdjacencyMatrixGraph graph = new AdjacencyMatrixGraph(5);
+        assertTrue(graph.addEdge(0, 1));
+        assertTrue(graph.edgeDoesExist(0, 1));
+        assertTrue(graph.edgeDoesExist(1, 0));
+        assertEquals(1, graph.numberOfEdges());
+
+        // Adding the same edge again should return false
+        assertFalse(graph.addEdge(0, 1));
+        assertFalse(graph.addEdge(5, 1));
+        assertFalse(graph.addEdge(-1, 1));
+    }
+
+    @Test
+    void testRemoveEdge() {
+        AdjacencyMatrixGraph graph = new AdjacencyMatrixGraph(5);
+        graph.addEdge(0, 1);
+        graph.addEdge(1, 2);
+
+        assertTrue(graph.removeEdge(0, 1));
+        assertFalse(graph.edgeDoesExist(0, 1));
+        assertFalse(graph.edgeDoesExist(1, 0));
+        assertEquals(1, graph.numberOfEdges());
+
+        assertFalse(graph.removeEdge(0, 3));
+        assertFalse(graph.removeEdge(5, 1));
+        assertFalse(graph.removeEdge(-1, 1));
+    }
+
+    @Test
+    void testVertexDoesExist() {
+        AdjacencyMatrixGraph graph = new AdjacencyMatrixGraph(5);
+        assertTrue(graph.vertexDoesExist(0));
+        assertTrue(graph.vertexDoesExist(4));
+        assertFalse(graph.vertexDoesExist(5));
+        assertFalse(graph.vertexDoesExist(-1));
+    }
+
+    @Test
+    void testDepthFirstOrder() {
+        AdjacencyMatrixGraph graph = new AdjacencyMatrixGraph(5);
+        graph.addEdge(0, 1);
+        graph.addEdge(0, 2);
+        graph.addEdge(1, 3);
+        graph.addEdge(2, 4);
+
+        List<Integer> dfs = graph.depthFirstOrder(0);
+        assertEquals(5, dfs.size());
+        assertEquals(0, dfs.getFirst());
+
+        assertTrue(dfs.containsAll(Arrays.asList(0, 1, 2, 3, 4)));
+
+        List<Integer> emptyDfs = graph.depthFirstOrder(5);
+        assertTrue(emptyDfs.isEmpty());
+    }
+
+    @Test
+    void testBreadthFirstOrder() {
+        AdjacencyMatrixGraph graph = new AdjacencyMatrixGraph(5);
+        graph.addEdge(0, 1);
+        graph.addEdge(0, 2);
+        graph.addEdge(1, 3);
+        graph.addEdge(2, 4);
+
+        List<Integer> bfs = graph.breadthFirstOrder(0);
+        assertEquals(5, bfs.size());
+        assertEquals(0, bfs.getFirst());
+
+        assertTrue(bfs.containsAll(Arrays.asList(0, 1, 2, 3, 4)));
+
+        List<Integer> emptyBfs = graph.breadthFirstOrder(5);
+        assertTrue(emptyBfs.isEmpty());
+    }
+
+    @Test
+    void testToString() {
+        AdjacencyMatrixGraph graph = new AdjacencyMatrixGraph(3);
+        graph.addEdge(0, 1);
+        graph.addEdge(1, 2);
+
+        String expected = "    0 1 2  \n"
+            + "0 : 0 1 0 \n"
+            + "1 : 1 0 1 \n"
+            + "2 : 0 1 0 \n";
+
+        assertEquals(expected, graph.toString());
+    }
+
+    @Test
+    void testCyclicGraph() {
+        AdjacencyMatrixGraph graph = new AdjacencyMatrixGraph(4);
+        graph.addEdge(0, 1);
+        graph.addEdge(1, 2);
+        graph.addEdge(2, 3);
+        graph.addEdge(3, 0);
+
+        List<Integer> dfs = graph.depthFirstOrder(0);
+        List<Integer> bfs = graph.breadthFirstOrder(0);
+
+        assertEquals(4, dfs.size());
+        assertEquals(4, bfs.size());
+        assertTrue(dfs.containsAll(Arrays.asList(0, 1, 2, 3)));
+        assertTrue(bfs.containsAll(Arrays.asList(0, 1, 2, 3)));
+    }
+
+    @Test
+    void testDisconnectedGraph() {
+        AdjacencyMatrixGraph graph = new AdjacencyMatrixGraph(5);
+        graph.addEdge(0, 1);
+        graph.addEdge(2, 3);
+
+        List<Integer> dfs = graph.depthFirstOrder(0);
+        List<Integer> bfs = graph.breadthFirstOrder(0);
+
+        assertEquals(2, dfs.size());
+        assertEquals(2, bfs.size());
+        assertTrue(dfs.containsAll(Arrays.asList(0, 1)));
+        assertTrue(bfs.containsAll(Arrays.asList(0, 1)));
+    }
+}