refactor: DecimalToAnyUsingStack (#5392)

src/test/java/com/thealgorithms/stacks/DecimalToAnyUsingStackTest.java

@@ -0,0 +1,45 @@
+package com.thealgorithms.stacks;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+class DecimalToAnyUsingStackTest {
+
+    @Test
+    void testConvertToBinary() {
+        assertEquals("0", DecimalToAnyUsingStack.convert(0, 2));
+        assertEquals("11110", DecimalToAnyUsingStack.convert(30, 2));
+    }
+
+    @Test
+    void testConvertToOctal() {
+        assertEquals("36", DecimalToAnyUsingStack.convert(30, 8));
+    }
+
+    @Test
+    void testConvertToDecimal() {
+        assertEquals("30", DecimalToAnyUsingStack.convert(30, 10));
+    }
+
+    @Test
+    void testConvertToHexadecimal() {
+        assertEquals("1E", DecimalToAnyUsingStack.convert(30, 16));
+    }
+
+    @Test
+    void testInvalidRadix() {
+        IllegalArgumentException thrown = assertThrows(IllegalArgumentException.class, () -> DecimalToAnyUsingStack.convert(30, 1));
+        assertEquals("Invalid radix: 1. Radix must be between 2 and 16.", thrown.getMessage());
+
+        thrown = assertThrows(IllegalArgumentException.class, () -> DecimalToAnyUsingStack.convert(30, 17));
+        assertEquals("Invalid radix: 17. Radix must be between 2 and 16.", thrown.getMessage());
+    }
+
+    @Test
+    void testNegativeNumber() {
+        IllegalArgumentException thrown = assertThrows(IllegalArgumentException.class, () -> DecimalToAnyUsingStack.convert(-30, 2));
+        assertEquals("Number must be non-negative.", thrown.getMessage());
+    }
+}