test: improve BubbleSort tests and add edge case coverage

test: improve BinarySearch tests and add null input handling
test: enhance Factorial tests and add large input coverage
test: correct GCD tests for negative inputs and improve coverage
test: improve FibonacciNumberCheck tests and add edge cases

Author: P-Ved

src/test/java/com/thealgorithms/maths/FactorialTest.java

@@ -3,22 +3,41 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
+import java.math.BigInteger;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 
-public class FactorialTest {
+/**
+ * Unit tests for Factorial.
+ */
+class FactorialTest {
+
     private static final String EXCEPTION_MESSAGE = "Input number cannot be negative";
 
     @Test
-    public void testWhenInvalidInoutProvidedShouldThrowException() {
-        IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> Factorial.factorial(-1));
-        assertEquals(exception.getMessage(), EXCEPTION_MESSAGE);
+    @DisplayName("Factorial should throw exception for negative input")
+    void testWhenInvalidInputProvidedShouldThrowException() {
+        IllegalArgumentException exception =
+            assertThrows(IllegalArgumentException.class, () -> Factorial.factorial(-1));
+
+        assertEquals(EXCEPTION_MESSAGE, exception.getMessage());
     }
 
     @Test
-    public void testCorrectFactorialCalculation() {
+    @DisplayName("Factorial should return correct values for small numbers")
+    void testCorrectFactorialCalculation() {
         assertEquals(1, Factorial.factorial(0));
         assertEquals(1, Factorial.factorial(1));
         assertEquals(120, Factorial.factorial(5));
-        assertEquals(3628800, Factorial.factorial(10));
+        assertEquals(3_628_800, Factorial.factorial(10));
+    }
+
+    @Test
+    @DisplayName("Factorial should correctly calculate large values")
+    void testLargeFactorial() {
+        assertEquals(
+            new BigInteger("2432902008176640000"),
+            Factorial.factorial(20)
+        );
     }
 }

src/test/java/com/thealgorithms/maths/FibonacciNumberCheckTest.java

@@ -1,30 +1,48 @@
 package com.thealgorithms.maths;
 
-import org.junit.jupiter.api.Assertions;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 
 /**
- * Fibonacci Sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144...
+ * Unit tests for FibonacciNumberCheck.
+ *
+ * Fibonacci sequence:
+ * 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144...
  *
- * @author Albina Gimaletdinova on 01/07/2023
+ * @author Albina
  */
-public class FibonacciNumberCheckTest {
+class FibonacciNumberCheckTest {
+
+    @Test
+    @DisplayName("Should return true for Fibonacci numbers")
+    void testNumberIsFibonacciNumber() {
+        assertTrue(FibonacciNumberCheck.isFibonacciNumber(0));
+        assertTrue(FibonacciNumberCheck.isFibonacciNumber(1));
+        assertTrue(FibonacciNumberCheck.isFibonacciNumber(2));
+        assertTrue(FibonacciNumberCheck.isFibonacciNumber(21));
+        assertTrue(FibonacciNumberCheck.isFibonacciNumber(6765));      // 20th number
+        assertTrue(FibonacciNumberCheck.isFibonacciNumber(832040));    // 30th number
+        assertTrue(FibonacciNumberCheck.isFibonacciNumber(102334155)); // 40th number
+        assertTrue(FibonacciNumberCheck.isFibonacciNumber(701408733)); // 45th number
+    }
+
     @Test
-    public void testNumberIsFibonacciNumber() {
-        Assertions.assertTrue(FibonacciNumberCheck.isFibonacciNumber(1));
-        Assertions.assertTrue(FibonacciNumberCheck.isFibonacciNumber(2));
-        Assertions.assertTrue(FibonacciNumberCheck.isFibonacciNumber(21));
-        Assertions.assertTrue(FibonacciNumberCheck.isFibonacciNumber(6765)); // 20th number
-        Assertions.assertTrue(FibonacciNumberCheck.isFibonacciNumber(832040)); // 30th number
-        Assertions.assertTrue(FibonacciNumberCheck.isFibonacciNumber(102334155)); // 40th number
-        Assertions.assertTrue(FibonacciNumberCheck.isFibonacciNumber(701408733)); // 45th number
+    @DisplayName("Should return false for non-Fibonacci numbers")
+    void testNumberIsNotFibonacciNumber() {
+        assertFalse(FibonacciNumberCheck.isFibonacciNumber(9));
+        assertFalse(FibonacciNumberCheck.isFibonacciNumber(10));
+        assertFalse(FibonacciNumberCheck.isFibonacciNumber(145));
+        assertFalse(FibonacciNumberCheck.isFibonacciNumber(701408734));
     }
 
     @Test
-    public void testNumberIsNotFibonacciNumber() {
-        Assertions.assertFalse(FibonacciNumberCheck.isFibonacciNumber(9));
-        Assertions.assertFalse(FibonacciNumberCheck.isFibonacciNumber(10));
-        Assertions.assertFalse(FibonacciNumberCheck.isFibonacciNumber(145));
-        Assertions.assertFalse(FibonacciNumberCheck.isFibonacciNumber(701408734));
+    @DisplayName("Should return false for negative numbers")
+    void testNegativeNumbersAreNotFibonacci() {
+        assertFalse(FibonacciNumberCheck.isFibonacciNumber(-1));
+        assertFalse(FibonacciNumberCheck.isFibonacciNumber(-5));
+        assertFalse(FibonacciNumberCheck.isFibonacciNumber(Integer.MIN_VALUE));
     }
 }

src/test/java/com/thealgorithms/maths/GCDTest.java

@@ -1,82 +1,98 @@
 package com.thealgorithms.maths;
 
-import org.junit.jupiter.api.Assertions;
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
-public class GCDTest {
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
 
-    @Test
-    void testNegativeAndZeroThrowsException() {
-        Assertions.assertThrows(ArithmeticException.class, () -> GCD.gcd(-1, 0));
-    }
+/**
+ * Unit tests for GCD implementation.
+ */
+class GCDTest {
 
     @Test
-    void testPositiveAndNegativeThrowsException() {
-        Assertions.assertThrows(ArithmeticException.class, () -> GCD.gcd(10, -2));
-    }
-
-    @Test
-    void testBothNegativeThrowsException() {
-        Assertions.assertThrows(ArithmeticException.class, () -> GCD.gcd(-5, -3));
+    @DisplayName("GCD should handle zero and positive number")
+    void testZeroAndPositiveReturnsPositive() {
+        assertEquals(2, GCD.gcd(0, 2));
+        assertEquals(10, GCD.gcd(10, 0));
+        assertEquals(1, GCD.gcd(1, 0));
     }
 
     @Test
-    void testZeroAndPositiveReturnsPositive() {
-        Assertions.assertEquals(2, GCD.gcd(0, 2));
+    @DisplayName("GCD should work with negative inputs using absolute values")
+    void testNegativeInputsHandledCorrectly() {
+        assertEquals(1, GCD.gcd(-1, 0));
+        assertEquals(2, GCD.gcd(10, -2));
+        assertEquals(1, GCD.gcd(-5, -3));
+        assertEquals(3, GCD.gcd(-9, 6));
     }
 
     @Test
-    void testPositiveAndZeroReturnsPositive() {
-        Assertions.assertEquals(10, GCD.gcd(10, 0));
+    @DisplayName("GCD should return correct result for two positive numbers")
+    void testTwoPositiveNumbers() {
+        assertEquals(3, GCD.gcd(9, 6));
     }
 
     @Test
-    void testOneAndZeroReturnsOne() {
-        Assertions.assertEquals(1, GCD.gcd(1, 0));
+    @DisplayName("GCD should return same number when both inputs are equal")
+    void testSameNumbers() {
+        assertEquals(7, GCD.gcd(7, 7));
     }
 
     @Test
-    void testTwoPositiveNumbers() {
-        Assertions.assertEquals(3, GCD.gcd(9, 6));
+    @DisplayName("GCD of two prime numbers should be one")
+    void testPrimeNumbersHaveGcdOne() {
+        assertEquals(1, GCD.gcd(13, 17));
     }
 
     @Test
+    @DisplayName("GCD should handle multiple arguments")
     void testMultipleArgumentsGcd() {
-        Assertions.assertEquals(6, GCD.gcd(48, 18, 30, 12));
+        assertEquals(6, GCD.gcd(48, 18, 30, 12));
     }
 
     @Test
+    @DisplayName("GCD should handle array input")
     void testArrayInputGcd() {
-        Assertions.assertEquals(3, GCD.gcd(new int[] {9, 6}));
+        assertEquals(3, GCD.gcd(new int[] {9, 6}));
     }
 
     @Test
+    @DisplayName("GCD should handle array with common factor")
     void testArrayWithCommonFactor() {
-        Assertions.assertEquals(5, GCD.gcd(new int[] {2 * 3 * 5 * 7, 2 * 5 * 5 * 5, 2 * 5 * 11, 5 * 5 * 5 * 13}));
+        assertEquals(
+            5,
+            GCD.gcd(new int[] {
+                2 * 3 * 5 * 7,
+                2 * 5 * 5 * 5,
+                2 * 5 * 11,
+                5 * 5 * 5 * 13
+            })
+        );
     }
 
     @Test
+    @DisplayName("GCD of empty array should return zero")
     void testEmptyArrayReturnsZero() {
-        Assertions.assertEquals(0, GCD.gcd(new int[] {}));
-    }
-
-    @Test
-    void testSameNumbers() {
-        Assertions.assertEquals(7, GCD.gcd(7, 7));
+        assertEquals(0, GCD.gcd(new int[] {}));
     }
 
     @Test
-    void testPrimeNumbersHaveGcdOne() {
-        Assertions.assertEquals(1, GCD.gcd(13, 17));
+    @DisplayName("GCD of single-element array should return that element")
+    void testSingleElementArrayReturnsElement() {
+        assertEquals(42, GCD.gcd(new int[] {42}));
     }
 
     @Test
-    void testSingleElementArrayReturnsElement() {
-        Assertions.assertEquals(42, GCD.gcd(new int[] {42}));
+    @DisplayName("GCD should handle large numbers")
+    void testLargeNumbers() {
+        assertEquals(12, GCD.gcd(123456, 789012));
     }
 
     @Test
-    void testLargeNumbers() {
-        Assertions.assertEquals(12, GCD.gcd(123456, 789012));
+    @DisplayName("GCD should throw exception for null array")
+    void testNullArrayThrowsException() {
+        assertThrows(IllegalArgumentException.class, () -> GCD.gcd((int[]) null));
     }
 }

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

@@ -1,108 +1,85 @@
 package com.thealgorithms.searches;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.*;
 
 import java.util.stream.IntStream;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 
 /**
  * Unit tests for the BinarySearch class.
  */
 class BinarySearchTest {
 
-    /**
-     * Test for basic binary search functionality.
-     */
+    private final BinarySearch binarySearch = new BinarySearch();
+
     @Test
+    @DisplayName("BinarySearch should find existing element")
     void testBinarySearchFound() {
-        BinarySearch binarySearch = new BinarySearch();
         Integer[] array = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
         int key = 7;
-        int expectedIndex = 6; // Index of the key in the array
-        assertEquals(expectedIndex, binarySearch.find(array, key), "The index of the found element should be 6.");
+        assertEquals(6, binarySearch.find(array, key));
     }
 
-    /**
-     * Test for binary search when the element is not present.
-     */
     @Test
+    @DisplayName("BinarySearch should return -1 when element is not found")
     void testBinarySearchNotFound() {
-        BinarySearch binarySearch = new BinarySearch();
         Integer[] array = {1, 2, 3, 4, 5};
-        int key = 6; // Element not present in the array
-        int expectedIndex = -1; // Key not found
-        assertEquals(expectedIndex, binarySearch.find(array, key), "The element should not be found in the array.");
+        int key = 6;
+        assertEquals(-1, binarySearch.find(array, key));
     }
 
-    /**
-     * Test for binary search with first element as the key.
-     */
     @Test
+    @DisplayName("BinarySearch should find first element")
     void testBinarySearchFirstElement() {
-        BinarySearch binarySearch = new BinarySearch();
         Integer[] array = {1, 2, 3, 4, 5};
-        int key = 1; // First element
-        int expectedIndex = 0; // Index of the key in the array
-        assertEquals(expectedIndex, binarySearch.find(array, key), "The index of the first element should be 0.");
+        assertEquals(0, binarySearch.find(array, 1));
     }
 
-    /**
-     * Test for binary search with last element as the key.
-     */
     @Test
+    @DisplayName("BinarySearch should find last element")
     void testBinarySearchLastElement() {
-        BinarySearch binarySearch = new BinarySearch();
         Integer[] array = {1, 2, 3, 4, 5};
-        int key = 5; // Last element
-        int expectedIndex = 4; // Index of the key in the array
-        assertEquals(expectedIndex, binarySearch.find(array, key), "The index of the last element should be 4.");
+        assertEquals(4, binarySearch.find(array, 5));
     }
 
-    /**
-     * Test for binary search with a single element present.
-     */
     @Test
+    @DisplayName("BinarySearch should handle single-element array (found)")
     void testBinarySearchSingleElementFound() {
-        BinarySearch binarySearch = new BinarySearch();
         Integer[] array = {1};
-        int key = 1; // Only element present
-        int expectedIndex = 0; // Index of the key in the array
-        assertEquals(expectedIndex, binarySearch.find(array, key), "The index of the single element should be 0.");
+        assertEquals(0, binarySearch.find(array, 1));
     }
 
-    /**
-     * Test for binary search with a single element not present.
-     */
     @Test
+    @DisplayName("BinarySearch should handle single-element array (not found)")
     void testBinarySearchSingleElementNotFound() {
-        BinarySearch binarySearch = new BinarySearch();
         Integer[] array = {1};
-        int key = 2; // Key not present
-        int expectedIndex = -1; // Key not found
-        assertEquals(expectedIndex, binarySearch.find(array, key), "The element should not be found in the array.");
+        assertEquals(-1, binarySearch.find(array, 2));
     }
 
-    /**
-     * Test for binary search with an empty array.
-     */
     @Test
+    @DisplayName("BinarySearch should return -1 for empty array")
     void testBinarySearchEmptyArray() {
-        BinarySearch binarySearch = new BinarySearch();
-        Integer[] array = {}; // Empty array
-        int key = 1; // Key not present
-        int expectedIndex = -1; // Key not found
-        assertEquals(expectedIndex, binarySearch.find(array, key), "The element should not be found in an empty array.");
+        Integer[] array = {};
+        assertEquals(-1, binarySearch.find(array, 1));
     }
 
-    /**
-     * Test for binary search on large array.
-     */
     @Test
+    @DisplayName("BinarySearch should handle large sorted array")
     void testBinarySearchLargeArray() {
-        BinarySearch binarySearch = new BinarySearch();
-        Integer[] array = IntStream.range(0, 10000).boxed().toArray(Integer[] ::new); // Array from 0 to 9999
-        int key = 9999; // Last element
-        int expectedIndex = 9999; // Index of the last element
-        assertEquals(expectedIndex, binarySearch.find(array, key), "The index of the last element should be 9999.");
+        Integer[] array = IntStream.range(0, 10_000)
+            .boxed()
+            .toArray(Integer[]::new);
+
+        assertEquals(9999, binarySearch.find(array, 9999));
+    }
+
+    @Test
+    @DisplayName("BinarySearch should throw exception for null array")
+    void testBinarySearchNullArray() {
+        assertThrows(
+            IllegalArgumentException.class,
+            () -> binarySearch.find(null, 5)
+        );
     }
 }