Use a debugger to test one hypothesis

Decide where to pause, which values to inspect, and what you expect

Suggested learning time: 50 minutes.

1. 1Input and predicted branch
2. 2Breakpoint
3. 3Observed value and stack
4. 4Revised explanation

Original learning map: arrows show the reading or decision sequence, not a measured execution trace.

Prerequisite chapter

Build safely and pass one test

Status of this chapter

This textbook was authored from reading sources. No actual repository builds, tests, debugging, API calls, or issue/PR posts were performed. Practical work below is an exercise to undertake; reading is not an execution result.

Learning objectives

• Decide where to pause, which values to inspect, and what you expect

Predict first

Write one sentence: 'With this input, execution should take this branch and produce this value.' Start from a local unit test, and place breakpoints before and after the transformation. The goal is to compare your prediction with what you observe, rather than to read every stack frame.

Observe the execution

Inspect variables, the stack, and conditional branches. With asynchronous execution or RPC, a single stack may not show the whole flow. Keep evidence that explains why the observations belong to the same call. Choose an area where external responses can be replaced with mocks.

Prepare logs for sharing

Logs may contain tokens, cookies, authentication headers, internal URLs, customer data, or personal file paths. Keep only the logs you need and remove confidential information. Follow the security policy for vulnerabilities instead of reporting them in a normal public issue.

Practical exercise: Practice testing one hypothesis with a debugger

1. Write your prediction in one sentence.
2. Launch the target test in an IDE debugger appropriate for its language.
3. Record the input, the value after the transformation, and the branch condition.
4. Describe the difference from your prediction and write a log summary that is safe to share.

Deliverable: Your prediction, observations, and revised explanation

Understanding checks

Answer in your own words before reading the answers. The answers and explanations below are for self-review, not automatic scores or execution results.

Is a difference between the documentation and behavior automatically a bug?

Answer: Check the version, configuration, and test conditions. Show the difference from the specification before forming a bug hypothesis.

Your learning progress

Recording mode: manual.

• Not started
• Read
• Tried
• Can explain

Do not mark an exercise as practiced merely because you viewed it.

Material used in this chapter

ApiClient implementation, databricks/databricks-sdk-py contribution and development guide, openai/codex contribution and development guide

Return to repository entry points · Offline experiment worksheet