Question: You are creating a Kotlin unit test library. What else should you add to make the following code compile without error?

1. The extension function should be marked public
2. Add the prefix operator to the shouldMatch extension function
3. The code is not legal in Kotlin (should be `println(msg.shouldEqual("test message"))`)
4. Add the prefix infix to the shouldMatch extension function

Answer: The correct answer of the above question is Option D:Add the prefix infix to the shouldMatch extension function