Keep the format and edge cases that matter, but replace private values with synthetic ones. For a CSV-to-JSON workflow, use a few rows that include an ordinary value, a blank field, and a quoted comma. Write down the expected output before running the workflow.
Confirm the input encoding, headers, delimiters, and any required permissions. Start with this small sample, inspect each step's output, then increase the size. Keep the original data separate so a failed transformation cannot overwrite it.
A sample is useful only if it resembles the troublesome case closely enough to reproduce the behavior.
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