test: GCDRecursion (#5361)

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

@@ -0,0 +1,48 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+public class GCDRecursionTest {
+
+    @ParameterizedTest
+    @CsvSource({"7, 5, 1", "9, 12, 3", "18, 24, 6", "36, 60, 12"})
+    void testGcdPositiveNumbers(int a, int b, int expectedGcd) {
+        assertEquals(expectedGcd, GCDRecursion.gcd(a, b));
+    }
+
+    @ParameterizedTest
+    @CsvSource({"0, 5, 5", "8, 0, 8"})
+    void testGcdOneZero(int a, int b, int expectedGcd) {
+        assertEquals(expectedGcd, GCDRecursion.gcd(a, b));
+    }
+
+    @Test
+    void testGcdBothZero() {
+        assertEquals(0, GCDRecursion.gcd(0, 0));
+    }
+
+    @ParameterizedTest
+    @ValueSource(ints = {-5, -15})
+    void testGcdNegativeNumbers(int negativeValue) {
+        assertThrows(ArithmeticException.class, () -> GCDRecursion.gcd(negativeValue, 15));
+        assertThrows(ArithmeticException.class, () -> GCDRecursion.gcd(15, negativeValue));
+    }
+
+    @ParameterizedTest
+    @CsvSource({"5, 5, 5", "8, 8, 8"})
+    void testGcdWithSameNumbers(int a, int b, int expectedGcd) {
+        assertEquals(expectedGcd, GCDRecursion.gcd(a, b));
+    }
+
+    @ParameterizedTest
+    @CsvSource({"7, 13, 1", "11, 17, 1"})
+    void testGcdWithPrimeNumbers(int a, int b, int expectedGcd) {
+        assertEquals(expectedGcd, GCDRecursion.gcd(a, b));
+    }
+}