42 lines
975 B
Markdown
42 lines
975 B
Markdown
---
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title: testing.assertEmpty() function
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description: The testing.assertEmpty() function tests if an input stream is empty.
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menu:
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v2_0_ref:
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name: testing.assertEmpty
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parent: Testing
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weight: 301
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---
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The `testing.assertEmpty()` function tests if an input stream is empty.
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If not empty, the function outputs an error.
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_**Function type:** Test_
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```js
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import "testing"
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testing.assertEmpty()
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```
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_The `testing.assertEmpty()` function can be used to perform in-line tests in a query._
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## Examples
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#### Check if there is a difference between streams
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This example uses the [`diff()` function](/flux/v0.x/functions/tests/diff)
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which outputs the diff for the two streams.
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The `.testing.assertEmpty()` function checks to see if the diff is empty.
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```js
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import "testing"
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got = from(bucket: "telegraf/autogen")
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|> range(start: -15m)
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want = from(bucket: "backup_telegraf/autogen")
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|> range(start: -15m)
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got
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|> diff(want: want)
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|> testing.assertEmpty()
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```
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