docs-v2/content/v2.0/reference/flux/functions/testing/assertempty.md

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---
title: testing.assertEmpty() function
description: The testing.assertEmpty() function tests if an input stream is empty.
menu:
v2_0_ref:
name: testing.assertEmpty
parent: Testing
weight: 301
---
The `testing.assertEmpty()` function tests if an input stream is empty.
If not empty, the function returns an error.
_**Function type:** Test_
```js
import "testing"
testing.assertEmpty()
```
_The `testing.assertEmpty()` function can be used to perform in-line tests in a query._
## Examples
#### Check if there is a difference between streams
This example uses the [`testing.diff()` function](/v2.0/reference/flux/functions/testing/diff)
which outputs the diff for the two streams.
The `.testing.assertEmpty()` function checks to see if the diff is empty.
```js
import "testing"
got = from(bucket: "example-bucket")
|> range(start: -15m)
want = from(bucket: "backup_example-bucket")
|> range(start: -15m)
got
|> testing.diff(want: want)
|> testing.assertEmpty()
```