refactor: DecimalToHexadecimal (#5337)

src/test/java/com/thealgorithms/conversions/DecimalToHexadecimalTest.java

@@ -0,0 +1,14 @@
+package com.thealgorithms.conversions;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+public class DecimalToHexadecimalTest {
+    @ParameterizedTest
+    @CsvSource({"0, 0", "1, 1", "10, a", "15, f", "16, 10", "255, ff", "190, be", "1800, 708"})
+    void testDecToHex(int decimal, String expectedHex) {
+        assertEquals(expectedHex, DecimalToHexadecimal.decToHex(decimal));
+    }
+}