Add BM25 Inverted Index Search Algorithm (#5615)

src/test/java/com/thealgorithms/searches/BM25InvertedIndexTest.java

@@ -0,0 +1,93 @@
+package com.thealgorithms.searches;
+
+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.List;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Test Cases for Inverted Index with BM25
+ * @author Prayas Kumar (https://github.com/prayas7102)
+ */
+
+class BM25InvertedIndexTest {
+
+    private static BM25InvertedIndex index;
+
+    @BeforeAll
+    static void setUp() {
+        index = new BM25InvertedIndex();
+        index.addMovie(1, "The Shawshank Redemption", 9.3, 1994, "Hope is a good thing. Maybe the best of things. And no good thing ever dies.");
+        index.addMovie(2, "The Godfather", 9.2, 1972, "I'm gonna make him an offer he can't refuse.");
+        index.addMovie(3, "The Dark Knight", 9.0, 2008, "You either die a hero or live long enough to see yourself become the villain.");
+        index.addMovie(4, "Pulp Fiction", 8.9, 1994, "You know what they call a Quarter Pounder with Cheese in Paris? They call it a Royale with Cheese.");
+        index.addMovie(5, "Good Will Hunting", 8.3, 1997, "Will Hunting is a genius and he has a good heart. The best of his abilities is yet to be explored.");
+        index.addMovie(6, "It's a Wonderful Life", 8.6, 1946, "Each man's life touches so many other lives. If he wasn't around, it would leave an awfully good hole.");
+        index.addMovie(7, "The Pursuit of Happyness", 8.0, 2006, "It was the pursuit of a better life, and a good opportunity to change things for the better.");
+        index.addMovie(8, "A Few Good Men", 7.7, 1992, "You can't handle the truth! This movie has a lot of good moments and intense drama.");
+    }
+
+    @Test
+    void testAddMovie() {
+        // Check that the index contains the correct number of movies
+        int moviesLength = index.getMoviesLength();
+        assertEquals(8, moviesLength);
+    }
+
+    @Test
+    void testSearchForTermFound() {
+        int expected = 1;
+        List<SearchResult> result = index.search("hope");
+        int actual = result.getFirst().getDocId();
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    void testSearchRanking() {
+        // Perform search for the term "good"
+        List<SearchResult> results = index.search("good");
+        assertFalse(results.isEmpty());
+
+        // Validate the ranking based on the provided relevance scores
+        assertEquals(6, results.get(0).getDocId()); // It's a Wonderful Life should be ranked 1st
+        assertEquals(7, results.get(1).getDocId()); // The Pursuit of Happyness should be ranked 2nd
+        assertEquals(5, results.get(2).getDocId()); // Good Will Hunting should be ranked 3rd
+        assertEquals(8, results.get(3).getDocId()); // A Few Good Men should be ranked 4th
+        assertEquals(1, results.get(4).getDocId()); // The Shawshank Redemption should be ranked 5th
+
+        // Ensure the relevance scores are in descending order
+        for (int i = 0; i < results.size() - 1; i++) {
+            assertTrue(results.get(i).getRelevanceScore() > results.get(i + 1).getRelevanceScore());
+        }
+    }
+
+    @Test
+    void testSearchForTermNotFound() {
+        List<SearchResult> results = index.search("nonexistent");
+        assertTrue(results.isEmpty());
+    }
+
+    @Test
+    void testSearchForCommonTerm() {
+        List<SearchResult> results = index.search("the");
+        assertFalse(results.isEmpty());
+        assertTrue(results.size() > 1);
+    }
+
+    @Test
+    void testBM25ScoreCalculation() {
+        List<SearchResult> results = index.search("cheese");
+        assertEquals(1, results.size());
+        assertEquals(4, results.getFirst().docId); // Pulp Fiction should have the highest score
+    }
+
+    @Test
+    void testCaseInsensitivity() {
+        List<SearchResult> resultsLowerCase = index.search("hope");
+        List<SearchResult> resultsUpperCase = index.search("HOPE");
+        assertEquals(resultsLowerCase, resultsUpperCase);
+    }
+}