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refactor: Enhance docs, code, add tests in PageRank (#6642)
This commit is contained in:
Hardik Pawar
319
src/test/java/com/thealgorithms/others/PageRankTest.java
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319
src/test/java/com/thealgorithms/others/PageRankTest.java
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package com.thealgorithms.others;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertNotNull;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import org.junit.jupiter.api.Test;
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/**
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* Test class for PageRank algorithm implementation
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*
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* @author Hardvan
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*/
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class PageRankTest {
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private static final double EPSILON = 0.0001; // Tolerance for floating point comparisons
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/**
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* Test basic PageRank calculation with a simple 3-node graph
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* Graph: 1 -> 2, 2 -> 3, 3 -> 1
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*/
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@Test
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void testSimpleThreeNodeGraph() {
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PageRank pageRank = new PageRank(3);
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// Create a simple circular graph: 1 -> 2 -> 3 -> 1
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int[][] adjacencyMatrix = new int[10][10];
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adjacencyMatrix[1][2] = 1; // Node 1 links to Node 2
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adjacencyMatrix[2][3] = 1; // Node 2 links to Node 3
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adjacencyMatrix[3][1] = 1; // Node 3 links to Node 1
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pageRank.setAdjacencyMatrix(adjacencyMatrix);
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double[] result = pageRank.calculatePageRank(3);
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// All nodes should have equal PageRank in a circular graph
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assertNotNull(result);
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assertEquals(result[1], result[2], EPSILON);
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assertEquals(result[2], result[3], EPSILON);
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}
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/**
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* Test PageRank with a two-node graph where one node points to another
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*/
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@Test
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void testTwoNodeGraph() {
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PageRank pageRank = new PageRank(2);
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// Node 1 links to Node 2
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pageRank.setEdge(1, 2, 1);
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double[] result = pageRank.calculatePageRank(2);
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// Node 2 should have higher PageRank than Node 1 (after 2 iterations)
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assertNotNull(result);
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assertEquals(0.2775, result[2], EPSILON);
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assertEquals(0.15, result[1], EPSILON);
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}
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/**
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* Test PageRank with a single node (no links)
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*/
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@Test
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void testSingleNode() {
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PageRank pageRank = new PageRank(1);
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double[] result = pageRank.calculatePageRank(1);
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// Single node should have (1-d) = 0.15 after applying damping
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assertNotNull(result);
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assertEquals(0.15, result[1], EPSILON);
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}
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/**
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* Test PageRank with a hub-and-spoke configuration
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* Node 1 is the hub, pointing to nodes 2, 3, and 4
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*/
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@Test
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void testHubAndSpokeGraph() {
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PageRank pageRank = new PageRank(4);
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// Hub node (1) links to all other nodes
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pageRank.setEdge(1, 2, 1);
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pageRank.setEdge(1, 3, 1);
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pageRank.setEdge(1, 4, 1);
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// All spokes link back to hub
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pageRank.setEdge(2, 1, 1);
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pageRank.setEdge(3, 1, 1);
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pageRank.setEdge(4, 1, 1);
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double[] result = pageRank.calculatePageRank(4);
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assertNotNull(result);
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// Hub should have higher PageRank
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assertEquals(result[2], result[3], EPSILON);
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assertEquals(result[3], result[4], EPSILON);
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}
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/**
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* Test PageRank with multiple iterations
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*/
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@Test
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void testMultipleIterations() {
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PageRank pageRank = new PageRank(3);
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pageRank.setEdge(1, 2, 1);
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pageRank.setEdge(2, 3, 1);
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pageRank.setEdge(3, 1, 1);
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double[] result2Iterations = pageRank.calculatePageRank(3, 0.85, 2, false);
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double[] result5Iterations = pageRank.calculatePageRank(3, 0.85, 5, false);
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assertNotNull(result2Iterations);
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assertNotNull(result5Iterations);
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}
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/**
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* Test getPageRank method for individual node
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*/
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@Test
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void testGetPageRank() {
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PageRank pageRank = new PageRank(2);
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pageRank.setEdge(1, 2, 1);
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pageRank.calculatePageRank(2);
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double node1PageRank = pageRank.getPageRank(1);
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double node2PageRank = pageRank.getPageRank(2);
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assertEquals(0.15, node1PageRank, EPSILON);
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assertEquals(0.2775, node2PageRank, EPSILON);
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}
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/**
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* Test getAllPageRanks method
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*/
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@Test
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void testGetAllPageRanks() {
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PageRank pageRank = new PageRank(2);
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pageRank.setEdge(1, 2, 1);
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pageRank.calculatePageRank(2);
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double[] allPageRanks = pageRank.getAllPageRanks();
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assertNotNull(allPageRanks);
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assertEquals(0.15, allPageRanks[1], EPSILON);
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assertEquals(0.2775, allPageRanks[2], EPSILON);
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}
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/**
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* Test that self-loops are not allowed
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*/
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@Test
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void testNoSelfLoops() {
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PageRank pageRank = new PageRank(2);
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// Try to set a self-loop
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pageRank.setEdge(1, 1, 1);
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pageRank.setEdge(1, 2, 1);
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double[] result = pageRank.calculatePageRank(2);
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assertNotNull(result);
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// Self-loop should be ignored
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}
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/**
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* Test exception when node count is too small
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*/
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@Test
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void testInvalidNodeCountTooSmall() {
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assertThrows(IllegalArgumentException.class, () -> new PageRank(0));
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}
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/**
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* Test exception when node count is too large
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*/
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@Test
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void testInvalidNodeCountTooLarge() {
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assertThrows(IllegalArgumentException.class, () -> new PageRank(11));
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}
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/**
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* Test exception for invalid damping factor (negative)
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*/
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@Test
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void testInvalidDampingFactorNegative() {
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PageRank pageRank = new PageRank(2);
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pageRank.setEdge(1, 2, 1);
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assertThrows(IllegalArgumentException.class, () -> pageRank.calculatePageRank(2, -0.1, 2, false));
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}
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/**
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* Test exception for invalid damping factor (greater than 1)
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*/
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@Test
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void testInvalidDampingFactorTooLarge() {
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PageRank pageRank = new PageRank(2);
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pageRank.setEdge(1, 2, 1);
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assertThrows(IllegalArgumentException.class, () -> pageRank.calculatePageRank(2, 1.5, 2, false));
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}
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/**
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* Test exception for invalid iterations (less than 1)
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*/
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@Test
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void testInvalidIterations() {
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PageRank pageRank = new PageRank(2);
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pageRank.setEdge(1, 2, 1);
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assertThrows(IllegalArgumentException.class, () -> pageRank.calculatePageRank(2, 0.85, 0, false));
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}
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/**
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* Test exception when getting PageRank for invalid node
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*/
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@Test
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void testGetPageRankInvalidNode() {
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PageRank pageRank = new PageRank(2);
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pageRank.calculatePageRank(2);
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assertThrows(IllegalArgumentException.class, () -> pageRank.getPageRank(3));
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}
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/**
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* Test exception when getting PageRank for node less than 1
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*/
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@Test
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void testGetPageRankNodeLessThanOne() {
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PageRank pageRank = new PageRank(2);
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pageRank.calculatePageRank(2);
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assertThrows(IllegalArgumentException.class, () -> pageRank.getPageRank(0));
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}
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/**
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* Test complex graph with multiple incoming and outgoing links
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*/
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@Test
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void testComplexGraph() {
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PageRank pageRank = new PageRank(4);
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// Create a more complex graph
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pageRank.setEdge(1, 2, 1);
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pageRank.setEdge(1, 3, 1);
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pageRank.setEdge(2, 3, 1);
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pageRank.setEdge(3, 4, 1);
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pageRank.setEdge(4, 1, 1);
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double[] result = pageRank.calculatePageRank(4);
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assertNotNull(result);
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// Node 3 should have high PageRank (receives links from nodes 1 and 2)
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// After 2 iterations, the sum will not equal total nodes
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double sum = result[1] + result[2] + result[3] + result[4];
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assertEquals(1.8325, sum, EPSILON);
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}
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/**
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* Test that PageRank values sum after 2 iterations
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*/
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@Test
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void testPageRankSum() {
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PageRank pageRank = new PageRank(5);
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// Create arbitrary graph
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pageRank.setEdge(1, 2, 1);
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pageRank.setEdge(2, 3, 1);
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pageRank.setEdge(3, 4, 1);
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pageRank.setEdge(4, 5, 1);
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pageRank.setEdge(5, 1, 1);
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double[] result = pageRank.calculatePageRank(5);
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double sum = 0;
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for (int i = 1; i <= 5; i++) {
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sum += result[i];
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}
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// Sum after 2 iterations with default damping factor
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assertEquals(2.11, sum, EPSILON);
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}
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/**
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* Test graph with isolated node (no incoming or outgoing links)
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*/
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@Test
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void testGraphWithIsolatedNode() {
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PageRank pageRank = new PageRank(3);
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// Node 1 and 2 are connected, Node 3 is isolated
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pageRank.setEdge(1, 2, 1);
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pageRank.setEdge(2, 1, 1);
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double[] result = pageRank.calculatePageRank(3);
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assertNotNull(result);
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// Isolated node should have some PageRank due to damping factor
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assertEquals(0.15, result[3], EPSILON);
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}
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/**
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* Test verbose mode (should not throw exception)
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*/
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@Test
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void testVerboseMode() {
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PageRank pageRank = new PageRank(2);
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pageRank.setEdge(1, 2, 1);
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// This should execute without throwing an exception
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double[] result = pageRank.calculatePageRank(2, 0.85, 2, true);
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assertNotNull(result);
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}
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}
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