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---
tags:
- golang
- testing
---
[[Testing Golang programs]]
Some functions print or log to stdout/stderr, but during testing we would like to capture this. Here is an example of how to do that:
```echo.go
package echo
import (
"fmt"
"io"
"os"
"strings"
)
var out io.Writer = os.Stdout
func echo() {
fmt.Fprintln(out, strings.Join(os.Args[1:], " "))
}
```
We define an io.Writer at the package level which is used to write our output to. During tests we can set this to be a buffer, ie:
```echo_test.go
package echo
import (
"bytes"
"testing"
)
func BenchmarkEcho(b *testing.B) {
out = new(bytes.Buffer)
for b.Loop() {
echo()
}
}
```
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