func (s *JujuOSEnvSuite) SetUpTest(c *gc.C) {
	s.oldEnvironment = make(map[string]string)
	for _, name := range []string{
		osenv.JujuXDGDataHomeEnvKey,
		osenv.JujuModelEnvKey,
		osenv.JujuLoggingConfigEnvKey,
		osenv.JujuFeatureFlagEnvKey,
		osenv.XDGDataHome,
	} {
		s.oldEnvironment[name] = os.Getenv(name)
		os.Setenv(name, "")
	}
	s.oldHomeEnv = utils.Home()
	s.oldJujuXDGDataHome = osenv.SetJujuXDGDataHome("")
	utils.SetHome("")

	// Update the feature flag set to be the requested initial set.
	// This works for both windows and unix, even though normally
	// the feature flags on windows are determined using the registry.
	// For tests, setting with the environment variable isolates us
	// from a single resource that was hitting contention during parallel
	// test runs.
	os.Setenv(osenv.JujuFeatureFlagEnvKey, s.initialFeatureFlags)
	featureflag.SetFlagsFromEnvironment(osenv.JujuFeatureFlagEnvKey)
}

func (s *flagSuite) TestParsing(c *gc.C) {
	s.PatchEnvironment("JUJU_TESTING_FEATURE", "MAGIC, test, space ")
	featureflag.SetFlagsFromEnvironment("JUJU_TESTING_FEATURE")
	c.Assert(featureflag.All(), jc.SameContents, []string{"magic", "space", "test"})
	c.Assert(featureflag.AsEnvironmentValue(), gc.Equals, "magic,space,test")
	c.Assert(featureflag.String(), gc.Equals, `"magic", "space", "test"`)
}

func (s *flagSuite) TestEmpty(c *gc.C) {
	s.PatchEnvironment("JUJU_TESTING_FEATURE", "")
	featureflag.SetFlagsFromEnvironment("JUJU_TESTING_FEATURE")
	c.Assert(featureflag.All(), gc.HasLen, 0)
	c.Assert(featureflag.AsEnvironmentValue(), gc.Equals, "")
	c.Assert(featureflag.String(), gc.Equals, "")
}

func init() {
	if FLAGSFROMENVIRONMENT == "true" {
		featureflag.SetFlagsFromEnvironment(osenv.JujuFeatureFlagEnvKey)
	} else {
		featureflag.SetFlagsFromRegistry(osenv.JujuRegistryKey, osenv.JujuFeatureFlagEnvKey)
	}
}

func (s *JujuOSEnvSuite) SetFeatureFlags(flag ...string) {
	flags := strings.Join(flag, ",")
	if err := os.Setenv(osenv.JujuFeatureFlagEnvKey, flags); err != nil {
		panic(err)
	}
	logger.Debugf("setting feature flags: %s", flags)
	featureflag.SetFlagsFromEnvironment(osenv.JujuFeatureFlagEnvKey)
}

// checkProviderType ensures the provider type is okay.
func checkProviderType(envType string) error {
	featureflag.SetFlagsFromEnvironment(osenv.JujuFeatureFlagEnvKey)
	flag, ok := provisionalProviders[envType]
	if ok && !featureflag.Enabled(flag) {
		msg := `the %q provider is provisional in this version of Juju. To use it anyway, set JUJU_DEV_FEATURE_FLAGS="%s" in your shell model`
		return errors.Errorf(msg, envType, flag)
	}
	return nil
}

func (s *flagSuite) TestEnabled(c *gc.C) {
	c.Assert(featureflag.Enabled(""), jc.IsTrue)
	c.Assert(featureflag.Enabled(" "), jc.IsTrue)
	c.Assert(featureflag.Enabled("magic"), jc.IsFalse)

	s.PatchEnvironment("JUJU_TESTING_FEATURE", "MAGIC")
	featureflag.SetFlagsFromEnvironment("JUJU_TESTING_FEATURE")

	c.Assert(featureflag.Enabled("magic"), jc.IsTrue)
	c.Assert(featureflag.Enabled("Magic"), jc.IsTrue)
	c.Assert(featureflag.Enabled(" MAGIC "), jc.IsTrue)
}

func init() {
	featureflag.SetFlagsFromEnvironment(osenv.JujuFeatureFlagEnvKey)
}

func (s *AddressableContainerSetupSuite) enableFeatureFlag() {
	s.SetFeatureFlags(feature.AddressAllocation)
	featureflag.SetFlagsFromEnvironment(osenv.JujuFeatureFlagEnvKey)
}

func setFeatureFlags(flags string) {
	if err := os.Setenv(osenv.JujuFeatureFlagEnvKey, flags); err != nil {
		panic(err)
	}
	featureflag.SetFlagsFromEnvironment(osenv.JujuFeatureFlagEnvKey)
}

func (s *discoverySuite) setLegacyUpstart(c *gc.C) {
	err := os.Setenv(osenv.JujuFeatureFlagEnvKey, feature.LegacyUpstart)
	c.Assert(err, jc.ErrorIsNil)
	featureflag.SetFlagsFromEnvironment(osenv.JujuFeatureFlagEnvKey)
}

// setUpFeatureFlags sets the feature flags from the environment.
func (s *JujuOSEnvSuite) setUpFeatureFlags(c *gc.C) {
	os.Setenv(osenv.JujuFeatureFlagEnvKey, s.initialFeatureFlags)
	featureflag.SetFlagsFromEnvironment(osenv.JujuFeatureFlagEnvKey)
}