---
lang: en
title: 'API docs: testlab.testfn'
keywords: LoopBack 4.0, LoopBack 4
sidebar: lb4_sidebar
permalink: /doc/en/lb4/apidocs.testlab.testfn.html
---

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[Home](./index.md) &gt; [@loopback/testlab](./testlab.md) &gt; [TestFn](./testlab.testfn.md)

## TestFn interface

\* LEGACY API FOR BACKWARDS COMPATIBILITY \*\*

<b>Signature:</b>

```typescript
export interface TestFn 
```

