对将数字转换为文本字符串的类进行自动测试

I created a PHP class that converts integers and floats to text strings. For example:

• 40300 -> forty-thousand three hundred
• 503.23 -> five hundred twenty-three and 23/100

I need to create an automated test for this class. (I'm doing this to demonstrate my knowledge of test-driven development as part of a programming challenge.)

Someone recommended that I look into PHPUnit as a starting point. What's the best way to write an automated test in PHP (using PHPUnit or another framework) for a simple class that converts integers and floats to text strings?