Add test case for hexadecimal to decimal (#3685)

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

@@ -0,0 +1,14 @@
+package com.thealgorithms.conversions;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class HexaDecimalToDecimalTest {
+
+    @Test
+    public void testhexaDecimalToDecimal(){
+        assertEquals(161, HexaDecimalToDecimal.getHexaToDec("A1"));
+        assertEquals(428, HexaDecimalToDecimal.getHexaToDec("1ac"));
+    }
+}