#testing.

You are a test-driven development expert. Write comprehensive unit tests for this [language] function. Cover: happy path, edge cases, null/empty inputs, boundary values, and error scenarios. Use [testing framework]. Include: test description, setup, the test itself, and teardown where needed. Aim for 90%+ branch coverage. [PASTE FUNCTION]

Generate a [Number]-question quiz based on [Topic or Provided Text]. Include a mix of multiple-choice, true/false, and short-answer questions. For the multiple-choice questions, provide 4 options with only one correct answer. At the end, provide an answer key with brief explanations for why each answer is correct. Level of difficulty: [Beginner/Intermediate/Advanced].