diff --git a/go-sandbox/activities/benign/activity.go b/go-sandbox/activities/benign/activity.go
new file mode 100644
index 0000000..708e258
--- /dev/null
+++ b/go-sandbox/activities/benign/activity.go
@@ -0,0 +1,24 @@
+package benign
+
+// @@@SNIPSTART go-benign-activity-error
+import (
+	"context"
+
+	"go.temporal.io/sdk/temporal"
+)
+
+func MyActivity(ctx context.Context) (string, error) {
+	result, err := callExternalService()
+	if err != nil {
+		// Mark this error as benign since it's expected
+		return "", temporal.NewApplicationErrorWithOptions(
+			err.Error(),
+			"",
+			temporal.ApplicationErrorOptions{
+				Category: temporal.ApplicationErrorCategoryBenign,
+			},
+		)
+	}
+	return result, nil
+}
+// @@@SNIPEND
diff --git a/go-sandbox/activities/benign/activity_test.go b/go-sandbox/activities/benign/activity_test.go
new file mode 100644
index 0000000..b9a5d0a
--- /dev/null
+++ b/go-sandbox/activities/benign/activity_test.go
@@ -0,0 +1,45 @@
+package benign_test
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+	"go.temporal.io/sdk/temporal"
+	"go.temporal.io/sdk/testsuite"
+
+	"my-org/quickstart/activities/benign"
+)
+
+type BenignErrorTestSuite struct {
+	suite.Suite
+	testsuite.WorkflowTestSuite
+}
+
+func TestBenignErrorTestSuite(t *testing.T) {
+	suite.Run(t, new(BenignErrorTestSuite))
+}
+
+func (s *BenignErrorTestSuite) Test_ErrorIsBenign() {
+	defer benign.SetCallExternalService(func() (string, error) { return "", benign.ErrNotReady })()
+	env := s.NewTestActivityEnvironment()
+	env.RegisterActivity(benign.MyActivity)
+
+	_, err := env.ExecuteActivity(benign.MyActivity)
+	var appErr *temporal.ApplicationError
+	s.True(errors.As(err, &appErr))
+	s.Equal(temporal.ApplicationErrorCategoryBenign, appErr.Category())
+	s.Contains(appErr.Error(), benign.ErrNotReady.Error())
+}
+
+func (s *BenignErrorTestSuite) Test_Success() {
+	defer benign.SetCallExternalService(func() (string, error) { return "ready", nil })()
+	env := s.NewTestActivityEnvironment()
+	env.RegisterActivity(benign.MyActivity)
+
+	val, err := env.ExecuteActivity(benign.MyActivity)
+	s.NoError(err)
+	var result string
+	s.NoError(val.Get(&result))
+	s.Equal("ready", result)
+}
diff --git a/go-sandbox/activities/benign/export_test.go b/go-sandbox/activities/benign/export_test.go
new file mode 100644
index 0000000..5e5c156
--- /dev/null
+++ b/go-sandbox/activities/benign/export_test.go
@@ -0,0 +1,8 @@
+package benign
+
+// SetCallExternalService lets tests in package benign_test replace the external call.
+func SetCallExternalService(f func() (string, error)) (restore func()) {
+	original := callExternalService
+	callExternalService = f
+	return func() { callExternalService = original }
+}
diff --git a/go-sandbox/activities/benign/external.go b/go-sandbox/activities/benign/external.go
new file mode 100644
index 0000000..ed6dbfd
--- /dev/null
+++ b/go-sandbox/activities/benign/external.go
@@ -0,0 +1,11 @@
+package benign
+
+import "errors"
+
+var ErrNotReady = errors.New("external service is not ready yet")
+
+// callExternalService stands in for a call to a service that is sometimes not
+// ready yet. Tests replace it to control the outcome.
+var callExternalService = func() (string, error) {
+	return "", ErrNotReady
+}