     let s10 = "\u{200B}hello\u{200B}"
     XCTAssertTrue(s10.capitalizedFirstCharacter() == s10)
   }
-
+  
   func testDecapitalizedFirstCharacter() {
     let s1 = "   hello world   "
     XCTAssertTrue(s1.decapitalizedFirstCharacter() == s1)

      let result4 = s.removingCharacters(in: .capitalizedLetters)
      XCTAssertTrue(result4 == "123Hello45 !World..5")
    }

    do {
      let s = "H ello"
      let result1 = s.removingCharacters(in: CharacterSet.letters.inverted)

    XCTAssertTrue("AaBbCc".replace("", with: "A") == "AaBbCc")
    XCTAssertTrue("AaBbCc".replace("AaBbCc", with: "123") == "123")
    XCTAssertTrue("aaBbCa".replace("a", with: "1") == "11BbC1")
    
    XCTAssertTrue("AaBbCc🤔".replace("🤔", with: "🤔🤔") == "AaBbCc🤔🤔")
    XCTAssertTrue("".replace("🤔", with: "🤔🤔") == "")
    XCTAssertTrue("".replace("", with: "🤔") == "")
    
    XCTAssertTrue("Italy 🇮🇹\u{200B}🇮🇹\u{200B}🇮🇹".replace("\u{200B}", with: " ") == "Italy 🇮🇹 🇮🇹 🇮🇹")
    
    XCTAssertTrue("AaBbCc".replace("a", with: "Z", caseSensitive: false) == "ZZBbCc")
    XCTAssertTrue("AaBbCc".replace("a", with: "a", caseSensitive: false) == "aaBbCc")
    XCTAssertTrue("AaBbCc".replace("a", with: "A", caseSensitive: false) == "AABbCc")
    XCTAssertTrue("AaBbCc".replace("", with: "A", caseSensitive: false) == "AaBbCc")
  }
  
  func testTrim() {
    var s1 = "   Hello World   "
    s1.trim()
    XCTAssertTrue(s1 == "Hello World")
  }
  
  func testTrimmed() {
    let s1 = "   Hello World   "
    XCTAssertTrue(s1.trimmedLeft() == "Hello World   ")
    XCTAssertTrue(s1.trimmedRight() == "   Hello World")
    XCTAssertTrue(s1.trimmed() == "Hello World")
    
    let s2 = "   \u{200B} Hello World   "
    XCTAssertTrue(s2.trimmedLeft() == "Hello World   ")
    XCTAssertTrue(s2.trimmed() == "Hello World")
    
    let s3 = "Hello World\n\n   "
    XCTAssertTrue(s3.trimmedRight() == "Hello World")
    XCTAssertTrue(s3.trimmed() == "Hello World")
    
    
    let s4 = "abcdefg"
    XCTAssertTrue(s4.trimmedRight(characterSet: .alphanumerics) == "")
    XCTAssertTrue(s4.trimmedLeft(characterSet: .alphanumerics) == "")
    
    let s5 = "  abcdefg  "
    XCTAssertTrue(s5.trimmedRight(characterSet: .alphanumerics) == "  abcdefg  ")
    XCTAssertTrue(s5.trimmedLeft(characterSet: .alphanumerics) == "  abcdefg  ")
    XCTAssertTrue(s5.trimmed() == "abcdefg")
  }
  
  func testCapitalizedFirstCharacter() {
    let s1 = "   hello world   "
    XCTAssertTrue(s1.capitalizedFirstCharacter() == s1)
