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Author: Jivan052

src/test/java/com/thealgorithms/backtracking/DijkstraAlgorithmTest.java

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+package com.thealgorithms.backtracking;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+public class DijkstraTest {
+
+    @Test
+    void testSingleNodeGraph() {
+        // Test case where graph has a single node
+        List<List<Dijkstra.Edge>> graph = new ArrayList<>();
+        graph.add(new ArrayList<>());
+
+        Dijkstra dijkstra = new Dijkstra();
+        int[] result = dijkstra.dijkstra(graph, 0);
+
+        // Since it's the only node, the distance to itself is 0
+        assertArrayEquals(new int[]{0}, result);
+    }
+
+    @Test
+    void testDisconnectedGraph() {
+        // Test case where graph is disconnected
+        int V = 3;  // 3 nodes in the graph
+        List<List<Dijkstra.Edge>> graph = new ArrayList<>();
+        for (int i = 0; i < V; i++) {
+            graph.add(new ArrayList<>());
+        }
+
+        Dijkstra dijkstra = new Dijkstra();
+        int[] result = dijkstra.dijkstra(graph, 0);
+
+        // Node 0 can only reach itself, others should be unreachable (infinity)
+        assertArrayEquals(new int[]{0, Integer.MAX_VALUE, Integer.MAX_VALUE}, result);
+    }
+
+    @Test
+    void testSimpleGraph() {
+        // Test case for a simple connected graph
+        int V = 4;
+        List<List<Dijkstra.Edge>> graph = new ArrayList<>();
+        for (int i = 0; i < V; i++) {
+            graph.add(new ArrayList<>());
+        }
+
+        // Add edges to the graph
+        graph.get(0).add(new Dijkstra.Edge(1, 1));
+        graph.get(0).add(new Dijkstra.Edge(2, 4));
+        graph.get(1).add(new Dijkstra.Edge(2, 2));
+        graph.get(1).add(new Dijkstra.Edge(3, 6));
+        graph.get(2).add(new Dijkstra.Edge(3, 3));
+
+        Dijkstra dijkstra = new Dijkstra();
+        int[] result = dijkstra.dijkstra(graph, 0);
+
+        // Expected shortest distances from node 0 to all other nodes
+        assertArrayEquals(new int[]{0, 1, 3, 6}, result);
+    }
+
+    @Test
+    void testInvalidSourceNode() {
+        int V = 3;
+        List<List<Dijkstra.Edge>> graph = new ArrayList<>();
+        for (int i = 0; i < V; i++) {
+            graph.add(new ArrayList<>());
+        }
+
+        Dijkstra dijkstra = new Dijkstra();
+
+        assertThrows(IndexOutOfBoundsException.class, () -> {
+            dijkstra.dijkstra(graph, 5);  
+        });
+    }
+
+    @Test
+    void testCyclicGraph() {
+        // Test case for a cyclic graph
+        int V = 3;
+        List<List<Dijkstra.Edge>> graph = new ArrayList<>();
+        for (int i = 0; i < V; i++) {
+            graph.add(new ArrayList<>());
+        }
+
+        graph.get(0).add(new Dijkstra.Edge(1, 2));
+        graph.get(1).add(new Dijkstra.Edge(2, 3));
+        graph.get(2).add(new Dijkstra.Edge(0, 4));
+
+        Dijkstra dijkstra = new Dijkstra();
+        int[] result = dijkstra.dijkstra(graph, 0);
+
+        assertArrayEquals(new int[]{0, 2, 5}, result);
+    }
+}