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Test Set - CI/CD Glossary Definition

A test set is data used exactly once at the end to estimate a finished models performance on unseen data.

A test set is data held out and touched only once, at the end, to estimate how a finished model will perform on truly unseen data. It must not influence any modeling decision.

The test set is the final, honest exam: using it during development would inflate the reported score.

Use it once

Every time you look at the test set and change the model, you leak information. Reserve it for a single final evaluation before deployment.

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