---
title: testing.diff() function
description: The testing.diff() function produces a diff between two streams.
aliases:
  - /influxdb/v2.0/reference/flux/functions/testing/diff/
  - /influxdb/v2.0/reference/flux/stdlib/testing/diff/
  - /influxdb/cloud/reference/flux/stdlib/testing/diff/
menu:
  flux_0_x_ref:
    name: testing.diff
    parent: testing
weight: 301
flux/v0.x/tags: [tests, transformations]
introduced: 0.18.0
---

The `testing.diff()` function produces a diff between two streams.

```js
import "testing"

testing.diff(
    got: stream2,
    want: stream1,
    epsilon: 0.000001,
    nansEqual: false,
    verbose: false,
)
```

It matches tables from each stream with the same group keys.
For each matched table, it produces a diff.
Any added or removed rows are added to the table as a row.
An additional string column with the name `diff` is created and contains a `-` if the
row was present in the `got` table and not in the `want` table or `+` if the opposite is true.

The diff function is guaranteed to emit at least one row if the tables are
different and no rows if the tables are the same. _The exact diff produced may change._

_The `testing.diff()` function can be used to perform in-line diffs in a query._

## Parameters

### got {data-type="stream of tables"}
Stream containing data to test.
Default is piped-forward data (`<-`).

### want {data-type="stream of tables"}
Stream that contains the expected data to test against.

### epsilon {data-type="float"}
Specifies how far apart two **float** values can be, but still considered equal.
Default is `0.000001`.

### nansEqual {data-type="bool"}
Consider `NaN` float values equal.
Default is `false`.

### verbose {data-type="bool"}
Include detailed differences in output.
Default is `false`.

## Examples

##### Diff separate streams
```js
import "testing"

want = from(bucket: "backup-example-bucket")
    |> range(start: -5m)
got = from(bucket: "example-bucket")
    |> range(start: -5m)

testing.diff(got: got, want: want)
```

##### Inline diff
```js
iimport "testing"

want = from(bucket: "backup-example-bucket") |> range(start: -5m)

from(bucket: "example-bucket")
    |> range(start: -5m)
    |> testing.diff(want: want)
```