Troubleshooting Data Generator Output Issues

Troubleshooting Data Generation

Generated data can fail in subtle ways that real data wouldn't. Understanding common failure modes helps you create more robust test datasets and catch generation bugs early.

Encoding Issues

Generated text containing Unicode characters (accents, CJK, emoji) may produce mojibake when imported into systems expecting ASCII or Latin-1. Always specify UTF-8 encoding explicitly in your output format. For CSV files, include a BOM (byte order mark) if the target system is Excel, which uses the BOM to detect encoding.

Format Mismatches

JSON generators may produce numbers where strings are expected, or vice versa. Phone numbers like "0012345678" lose their leading zero when treated as numbers. Zip codes, IDs, and similar fields should always be generated as strings. Dates in ambiguous formats (01/02/2025 — January 2nd or February 1st?) cause silent data corruption across systems with different locale settings.

Referential Integrity Failures

When generating related datasets, foreign key references to non-existent parent records cause import failures. Generate parent tables first, collect their IDs, and use only those IDs when generating child records. Verify referential integrity before export with a validation pass that checks every FK reference.

Value Distribution Problems

Uniform random distributions rarely match real-world patterns. If 80% of your real users are in 3 countries, your test data should reflect that. Zipf distributions for name popularity, log-normal for purchase amounts, and exponential for inter-event times are more realistic than uniform random sampling.

Troubleshooting Checklist

Verify the character encoding of your output file. Check that numeric fields with leading zeros are preserved as strings. Validate all foreign key references point to existing parent records. Compare value distributions against production data patterns. Test import into the target system with a small sample before generating the full dataset.