This commit is related to the article BAEL-6988 (#15149)

This commit aims to add a test class "HexToIntConversionUnitTest.java" that provides several ways to convert Hex string into int.

core-java-modules/core-java-hex/test/java/com/baeldung/hextoint/HexToIntConversionUnitTest.java

@@ -0,0 +1,42 @@
+package com.baeldung.hextoint;
+
+import org.junit.Test;
+
+import java.math.BigInteger;
+
+import static org.junit.Assert.assertEquals;
+
+public class HexToIntConversionUnitTest {
+
+    @Test
+    public void givenValidHexString_whenUsingParseInt_thenExpectCorrectDecimalValue() {
+        String hexString = "0x00FF00";
+        int expectedDecimalValue = 65280;
+
+        int decimalValue = Integer.parseInt(hexString.substring(2), 16);
+
+        assertEquals(expectedDecimalValue, decimalValue);
+    }
+
+    @Test
+    public void givenValidHexString_whenUsingIntegerDecode_thenExpectCorrectDecimalValue() {
+        String hexString = "0x00FF00";
+        int expectedDecimalValue = 65280;
+
+        int decimalValue = Integer.decode(hexString);
+
+        assertEquals(expectedDecimalValue, decimalValue);
+    }
+
+    @Test
+    public void givenValidHexString_whenUsingBigInteger_thenExpectCorrectDecimalValue() {
+        String hexString = "0x00FF00";
+        int expectedDecimalValue = 65280;
+
+        BigInteger bigIntegerValue = new BigInteger(hexString.substring(2), 16);
+        int decimalValue = bigIntegerValue.intValue();
+        assertEquals(expectedDecimalValue, decimalValue);
+    }
+
+
+}