> ## Documentation Index
> Fetch the complete documentation index at: https://docs.openlayer.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Training-validation leakage

> Learn how to use the training-validation leakage test

## Definition

The training-validation lekage test allows you to detect training rows that are also present in the validation dataset.

## Taxonomy

* **Task types**: LLM, tabular classification, tabular regression, text classification.
* **Availability**: development (Continuously evaluate your models and datasets as you iterate on their versions.).

## Why it matters

* The training and validation datasets must be completely disjoint. Otherwise, all evaluation insights extracted from the validation set are unreliable and overly optimistic.

## Test configuration examples

If you are writing a `tests.json`, here are a few valid configurations for the character length test:

```json Development theme={null}
[
  {
    "name": "No training-validation leakage",
    "description": "Asserts that no rows from the validation set are present in the training set",
    "type": "consistency",
    "subtype": "trainValLeakageRowCount",
    "thresholds": [
      {
        "insightName": "trainValLeakageRowCount",
        "measurement": "trainValLeakageRowCount",
        "operator": "<=",
        "value": 0
      }
    ],
    "subpopulationFilters": null,
    "mode": "development",
    "usesValidationDataset": true,
    "usesTrainingDataset": true,
    "usesMlModel": false,
    "syncId": "b4dee7dc-4f15-48ca-a282-63e2c04e0689"
  }
]
```


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