chore: isHex string extension tests

Author: JeneaVranceanu

Tests/web3swiftTests/localTests/String+ExtensionTests.swift.swift

@@ -0,0 +1,31 @@
+//
+//  String+ExtensionTests.swift
+//
+//  Created by JeneaVranceanu on 26.11.2023.
+//
+
+import Foundation
+import XCTest
+
+class StringExtensionsTest: XCTestCase {
+
+    func testIsHex() throws {
+        XCTAssertTrue("0x".isHex)
+        XCTAssertTrue("0xF".isHex)
+        XCTAssertTrue("F".isHex)
+        XCTAssertTrue("0xFF".isHex)
+        XCTAssertTrue("0x0123456789abcdefABCDEF".isHex)
+        XCTAssertTrue("0123456789abcdefABCDEF".isHex)
+        XCTAssertTrue("0123456789abcdefABCDEF ".isHex)
+        XCTAssertTrue(" 0123456789abcdefABCDEF ".isHex)
+        XCTAssertTrue(" 0123456789abcdefABCDEF".isHex)
+
+        XCTAssertFalse("".isHex)
+        XCTAssertFalse("-".isHex)
+        XCTAssertFalse("xyz".isHex)
+        XCTAssertFalse("0xCAFEQ".isHex)
+        XCTAssertFalse("R0123456789abcdefABCDEF ".isHex)
+        XCTAssertFalse(" R0123456789abcdefABCDEFT ".isHex)
+    }
+
+}