Add tests, remove main, add negativity test in Fibonacci.java (#5645)

Author: Hardvan

DIRECTORY.md

@@ -791,6 +791,7 @@
             * [DPTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/DPTest.java)
             * [EditDistanceTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/EditDistanceTest.java)
             * [EggDroppingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/EggDroppingTest.java)
+            * [FibonacciTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/FibonacciTest.java)
             * [KnapsackMemoizationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/KnapsackMemoizationTest.java)
             * [KnapsackTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/KnapsackTest.java)
             * [LevenshteinDistanceTests](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LevenshteinDistanceTests.java)

src/main/java/com/thealgorithms/dynamicprogramming/Fibonacci.java

@@ -2,7 +2,6 @@
 
 import java.util.HashMap;
 import java.util.Map;
-import java.util.Scanner;
 
 /**
  * @author Varun Upadhyay (https://github.com/varunu28)
@@ -11,27 +10,19 @@ public final class Fibonacci {
     private Fibonacci() {
     }
 
-    private static final Map<Integer, Integer> CACHE = new HashMap<>();
-
-    public static void main(String[] args) {
-        // Methods all returning [0, 1, 1, 2, 3, 5, ...] for n = [0, 1, 2, 3, 4, 5, ...]
-        Scanner sc = new Scanner(System.in);
-        int n = sc.nextInt();
-
-        System.out.println(fibMemo(n));
-        System.out.println(fibBotUp(n));
-        System.out.println(fibOptimized(n));
-        System.out.println(fibBinet(n));
-        sc.close();
-    }
+    static final Map<Integer, Integer> CACHE = new HashMap<>();
 
     /**
      * This method finds the nth fibonacci number using memoization technique
      *
      * @param n The input n for which we have to determine the fibonacci number
      * Outputs the nth fibonacci number
+     * @throws IllegalArgumentException if n is negative
      */
     public static int fibMemo(int n) {
+        if (n < 0) {
+            throw new IllegalArgumentException("Input n must be non-negative");
+        }
         if (CACHE.containsKey(n)) {
             return CACHE.get(n);
         }
@@ -52,8 +43,12 @@ public static int fibMemo(int n) {
      *
      * @param n The input n for which we have to determine the fibonacci number
      * Outputs the nth fibonacci number
+     * @throws IllegalArgumentException if n is negative
      */
     public static int fibBotUp(int n) {
+        if (n < 0) {
+            throw new IllegalArgumentException("Input n must be non-negative");
+        }
         Map<Integer, Integer> fib = new HashMap<>();
 
         for (int i = 0; i <= n; i++) {
@@ -80,9 +75,13 @@ public static int fibBotUp(int n) {
      * Time Complexity will be O(n)
      * <p>
      * Whereas , the above functions will take O(n) Space.
+     * @throws IllegalArgumentException if n is negative
      * @author Shoaib Rayeen (https://github.com/shoaibrayeen)
      */
     public static int fibOptimized(int n) {
+        if (n < 0) {
+            throw new IllegalArgumentException("Input n must be non-negative");
+        }
         if (n == 0) {
             return 0;
         }
@@ -105,9 +104,14 @@ public static int fibOptimized(int n) {
      * = 1.6180339887... Now, let's look at Binet's formula: Sn = Φⁿ–(– Φ⁻ⁿ)/√5 We first calculate
      * the squareRootof5 and phi and store them in variables. Later, we apply Binet's formula to get
      * the required term. Time Complexity will be O(1)
+     * @param n The input n for which we have to determine the fibonacci number
+     * Outputs the nth fibonacci number
+     * @throws IllegalArgumentException if n is negative
      */
-
     public static int fibBinet(int n) {
+        if (n < 0) {
+            throw new IllegalArgumentException("Input n must be non-negative");
+        }
         double squareRootOf5 = Math.sqrt(5);
         double phi = (1 + squareRootOf5) / 2;
         return (int) ((Math.pow(phi, n) - Math.pow(-phi, -n)) / squareRootOf5);

src/test/java/com/thealgorithms/dynamicprogramming/FibonacciTest.java

@@ -0,0 +1,89 @@
+package com.thealgorithms.dynamicprogramming;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class FibonacciTest {
+
+    @BeforeEach
+    void setUp() {
+        // Clear the cache before each test to avoid interference
+        Fibonacci.CACHE.clear();
+    }
+
+    @Test
+    void testFibMemo() {
+        // Test memoization method
+        assertEquals(0, Fibonacci.fibMemo(0));
+        assertEquals(1, Fibonacci.fibMemo(1));
+        assertEquals(1, Fibonacci.fibMemo(2));
+        assertEquals(2, Fibonacci.fibMemo(3));
+        assertEquals(3, Fibonacci.fibMemo(4));
+        assertEquals(5, Fibonacci.fibMemo(5));
+        assertEquals(8, Fibonacci.fibMemo(6));
+        assertEquals(13, Fibonacci.fibMemo(7));
+        assertEquals(21, Fibonacci.fibMemo(8));
+        assertEquals(34, Fibonacci.fibMemo(9));
+        assertEquals(55, Fibonacci.fibMemo(10));
+    }
+
+    @Test
+    void testFibBotUp() {
+        // Test bottom-up method
+        assertEquals(0, Fibonacci.fibBotUp(0));
+        assertEquals(1, Fibonacci.fibBotUp(1));
+        assertEquals(1, Fibonacci.fibBotUp(2));
+        assertEquals(2, Fibonacci.fibBotUp(3));
+        assertEquals(3, Fibonacci.fibBotUp(4));
+        assertEquals(5, Fibonacci.fibBotUp(5));
+        assertEquals(8, Fibonacci.fibBotUp(6));
+        assertEquals(13, Fibonacci.fibBotUp(7));
+        assertEquals(21, Fibonacci.fibBotUp(8));
+        assertEquals(34, Fibonacci.fibBotUp(9));
+        assertEquals(55, Fibonacci.fibBotUp(10));
+    }
+
+    @Test
+    void testFibOptimized() {
+        // Test optimized Fibonacci method
+        assertEquals(0, Fibonacci.fibOptimized(0));
+        assertEquals(1, Fibonacci.fibOptimized(1));
+        assertEquals(1, Fibonacci.fibOptimized(2));
+        assertEquals(2, Fibonacci.fibOptimized(3));
+        assertEquals(3, Fibonacci.fibOptimized(4));
+        assertEquals(5, Fibonacci.fibOptimized(5));
+        assertEquals(8, Fibonacci.fibOptimized(6));
+        assertEquals(13, Fibonacci.fibOptimized(7));
+        assertEquals(21, Fibonacci.fibOptimized(8));
+        assertEquals(34, Fibonacci.fibOptimized(9));
+        assertEquals(55, Fibonacci.fibOptimized(10));
+    }
+
+    @Test
+    void testFibBinet() {
+        // Test Binet's formula method
+        assertEquals(0, Fibonacci.fibBinet(0));
+        assertEquals(1, Fibonacci.fibBinet(1));
+        assertEquals(1, Fibonacci.fibBinet(2));
+        assertEquals(2, Fibonacci.fibBinet(3));
+        assertEquals(3, Fibonacci.fibBinet(4));
+        assertEquals(5, Fibonacci.fibBinet(5));
+        assertEquals(8, Fibonacci.fibBinet(6));
+        assertEquals(13, Fibonacci.fibBinet(7));
+        assertEquals(21, Fibonacci.fibBinet(8));
+        assertEquals(34, Fibonacci.fibBinet(9));
+        assertEquals(55, Fibonacci.fibBinet(10));
+    }
+
+    @Test
+    void testNegativeInput() {
+        // Test negative input; Fibonacci is not defined for negative numbers
+        assertThrows(IllegalArgumentException.class, () -> { Fibonacci.fibMemo(-1); });
+        assertThrows(IllegalArgumentException.class, () -> { Fibonacci.fibBotUp(-1); });
+        assertThrows(IllegalArgumentException.class, () -> { Fibonacci.fibOptimized(-1); });
+        assertThrows(IllegalArgumentException.class, () -> { Fibonacci.fibBinet(-1); });
+    }
+}