Go package `tmpenv`

tmpenv is a small Go package for replacing environment variables temporarily.

Setting temporary environment variables and restoring them are common pattern on testing. However, they have a pitfall since setting empty value to environment variable is different from unsetting environment variable.

tmpenv helps you to do the pattern correctly with less lines.

Installation

$ go get -u github.com/rhysd/go-tmpenv

Usage

You can find some examples at example tests.

To ensure to restore all existing environment variables and to remove all temporary environment variables, tmpenv.All() is useful. Even if environment variables are set via os.Setenv(), Restore() method can resture the original values.

import (
	"github.com/rhysd/go-tmpenv"
	"testing"
)

func TestFoo(t *testing.T) {
	// Captures all environment variables
	guard := tmpenv.All()

	// Ensure to restore the captured variables with 'defer'
	defer guard.Restore()

	// Modify existing environment variable
	os.Setenv("LANG", "C")

	// Set new environment variable
	os.Setenv("FOO_ANSWER", "42")

	// Do some tests...

	// $LANG will be restored to original value and $FOO_ANSWER will be removed.
	// And other all environment variables will be restored to original values.
}

If you're interested in specific environment variables:

import (
	"github.com/rhysd/go-tmpenv"
	"testing"
)

func TestFoo(t *testing.T) {
	// $CONFIG_FOO and $CONFIG_BAR are set to "aaa" and "bbb" temporarily.
	// They will be restored to original values when calling Restore() method.
	guard, err := tmpenv.Setenvs(map[string]string{
		"CONFIG_FOO": "aaa",
		"CONFIG_BAR": "bbb",
	})
	if err != nil {
		panic(err)
	}

	// Ensure to restore the captured variables with 'defer'
	defer guard.Restore()

	// Do some tests...

	// $CONFIG_FOO and $CONFIG_BAR will be restored. When they were already existing,
	// they will be restored to original values. If they were not existing, they will
	// will be removed.
}

Following is the same as above, but adding variables one by one:

import (
	"github.com/rhysd/go-tmpenv"
	"testing"
)

func TestFoo(t *testing.T) {
	guard := tmpenv.New()

	// Ensure to restore the captured variables with 'defer'
	defer guard.Restore()

	// $CONFIG_FOO and $CONFIG_BAR are set to "aaa" and "bbb" temporarily.
	// They will be restored to original values when calling Restore() method.
	// You need to use guard.Setenv instead of os.Setenv to notify which environment variable
	// was temporarily set to `guard` object.
	guard.Setenv("CONFIG_FOO", "aaa")
	guard.Setenv("CONFIG_BAR", "bbb")

	// Do some tests...

	// $CONFIG_FOO and $CONFIG_BAR will be restored. When they were already existing,
	// they will be restored to original values. If they were not existing, they will
	// will be removed.
}

You can also declare the environment variables which should be restored at tmpenv.New().

import (
	"github.com/rhysd/go-tmpenv"
	"testing"
)

func TestFoo(t *testing.T) {
	// Let's say $CONFIG_FOO is already existing, and $CONFIG_BAR does not exist

	guard := tmpenv.New("CONFIG_FOO", "CONFIG_BAR")

	// Ensure to restore the captured variables with 'defer'
	defer guard.Restore()

	os.Setenv("CONFIG_FOO", "some value")
	os.Setenv("CONFIG_BAR", "some value")

	// Do some tests...

	// $CONFIG_FOO will be restored to original value and $CONFIG_BAR will be unset.
}

When you want to clear environment variables temporarily, tmpenv.Unset function or Unsetenv method are available.

import (
	"github.com/rhysd/go-tmpenv"
	"testing"
)

func TestFoo(t *testing.T) {
	// Let's say $CONFIG_FOO and $CONFIG_BAR are already existing

	// Remember $CONFIG_FOO value and unset it
	guard := tmpenv.Unset("CONFIG_FOO")

	// Ensure to restore the captured variables with 'defer'
	defer guard.Restore()

	// Unsetenv method also unset the environment variable with remembering the original value
	guard.Unsetenv("CONFIG_BAR")

	// Here, $CONFIG_FOO and $CONFIG_BAR are not set

	// Do some tests...

	// $CONFIG_FOO and $CONFIG_BAR will be restored to original values.
}