add a test for trace

[lijunchen]

No description provided.

[peter-jerry-ye-code-review]

From the provided git diff output, here are three observations that could be potential issues or areas for improvement:

1. Unused Imports:

   • The use serde::{Deserialize, Serialize}; statement is added, but it is not immediately clear if it is used within the modified file. If Serialize and Deserialize are not used anywhere in the new code, it would be better to remove these imports to avoid clutter and potential dead code.

2. Error Handling in serde_json::from_str:

   • The line let j: TraceResult = serde_json::from_str(&s).unwrap(); uses .unwrap(), which will cause the program to panic if the JSON deserialization fails. It is generally better to handle the error properly, perhaps by using a match statement or the ? operator if within a function that returns Result.

3. Magic Numbers in Assertions:

   • The assertion assert!(e.dur > 0); checks that the duration is greater than zero. While this might be correct for the current context, it's generally good practice to avoid magic numbers by defining them as constants or using descriptive variable names to make the code more readable and maintainable.

These suggestions aim to improve code readability, maintainability, and robustness by addressing potential issues related to unused code, error handling, and magic numbers.