自己想一个需求不要太复杂-- 让AI实现下， 功能，单元测试，注释，功能说明，解决报错

好的，让我们设计一个简单的文本计数器应用。这个应用接收一段字符串作为输入，然后返回其中单词的数量。我们首先会创建一个名为`WordCounter`的简单类，并包含两个方法：一个用于计算单词数，另一个用于处理用户输入并调用这个方法。

# WordCounter.py

class WordCounter:
    """
    A class that counts the number of words in a given input string.
    
    Attributes:
        None (all functionality is within methods)
    """

    def count_words(self, text):
        """
        Calculate the number of words in the provided text.

        Args:
            text (str): The input text to count words from.

        Returns:
            int: The total word count.
        """
        # Remove punctuation and split by whitespace
        words = text.translate(str.maketrans('', '', string.punctuation)).split()
        
        # Return the length of the list (number of words)
        return len(words)

    def process_input(self, user_text):
        """
        Takes user input, removes punctuation, counts words, and returns the result.

        Args:
            user_text (str): The user's input to be counted.

        Returns:
            int: The word count or an error message if input is empty or not a string.
        """
        try:
            # Check if input is valid
            if isinstance(user_text, str) and user_text.strip():
                return self.count_words(user_text)
            else:
                return "Error: Please enter a non-empty string."
        except Exception as e:
            return f"Error: {str(e)}"

# Unit test example
import unittest
from WordCounter import WordCounter

class TestWordCounter(unittest.TestCase):
    def setUp(self):
        self.word_counter = WordCounter()

    def test_count_words(self):
        self.assertEqual(self.word_counter.count_words("Hello, world!"), 2)
        self.assertEqual(self.word_counter.count_words(""), 0)
        self.assertEqual(self.word_counter.count_words("This is a test."), 4)

    def test_process_input(self):
        self.assertEqual(self.word_counter.process_input("Hello, world!"), 2)
        self.assertEqual(self.word_counter.process_input(""), "Error: Please enter a non-empty string.")
        self.assertIsInstance(self.word_counter.process_input(123), str)

if __name__ == "__main__":
    unittest.main()