diff --git a/cmd/af/cmd/hello.go b/cmd/af/cmd/hello.go
new file mode 100644
index 0000000..6a1b6ab
--- /dev/null
+++ b/cmd/af/cmd/hello.go
@@ -0,0 +1,19 @@
+package cmd
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+)
+
+var helloCmd = &cobra.Command{
+	Use:   "hello",
+	Short: "Print a greeting",
+	Run: func(cmd *cobra.Command, args []string) {
+		fmt.Fprintln(cmd.OutOrStdout(), "hello world")
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(helloCmd)
+}
diff --git a/cmd/af/cmd/hello_test.go b/cmd/af/cmd/hello_test.go
new file mode 100644
index 0000000..c8afa93
--- /dev/null
+++ b/cmd/af/cmd/hello_test.go
@@ -0,0 +1,20 @@
+package cmd
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestHelloCmdPrintsHelloWorld(t *testing.T) {
+	var buf bytes.Buffer
+	helloCmd.SetOut(&buf)
+	t.Cleanup(func() { helloCmd.SetOut(nil) })
+
+	helloCmd.Run(helloCmd, nil)
+
+	got := buf.String()
+	want := "hello world\n"
+	if got != want {
+		t.Fatalf("hello output = %q, want %q", got, want)
+	}
+}