diff --git a/cli/cmd/convert.go b/cli/cmd/convert.go
index 1d0734fc..5de4064b 100644
--- a/cli/cmd/convert.go
+++ b/cli/cmd/convert.go
@@ -43,6 +43,6 @@ func init() {
 }
 
 func runConvert(cmd *cobra.Command, args []string) error {
-	fmt.Fprintln(cmd.OutOrStdout(), "not yet implemented")
-	return nil
+	cmd.SilenceUsage = true
+	return fmt.Errorf("%s is not yet implemented", cmd.CommandPath())
 }
diff --git a/cli/cmd/plugin/install.go b/cli/cmd/plugin/install.go
index 7a77f235..eebc59f9 100644
--- a/cli/cmd/plugin/install.go
+++ b/cli/cmd/plugin/install.go
@@ -33,6 +33,6 @@ func init() {
 }
 
 func runPluginInstall(cmd *cobra.Command, args []string) error {
-	fmt.Fprintln(cmd.OutOrStdout(), "not yet implemented")
-	return nil
+	cmd.SilenceUsage = true
+	return fmt.Errorf("%s is not yet implemented", cmd.CommandPath())
 }
diff --git a/cli/cmd/plugin/remove.go b/cli/cmd/plugin/remove.go
index 38df2259..1f1cfd89 100644
--- a/cli/cmd/plugin/remove.go
+++ b/cli/cmd/plugin/remove.go
@@ -30,6 +30,6 @@ var removeCmd = &cobra.Command{
 }
 
 func runPluginRemove(cmd *cobra.Command, args []string) error {
-	fmt.Fprintln(cmd.OutOrStdout(), "not yet implemented")
-	return nil
+	cmd.SilenceUsage = true
+	return fmt.Errorf("%s is not yet implemented", cmd.CommandPath())
 }
diff --git a/cli/cmd/stubs_test.go b/cli/cmd/stubs_test.go
new file mode 100644
index 00000000..e405a22b
--- /dev/null
+++ b/cli/cmd/stubs_test.go
@@ -0,0 +1,70 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
+)
+
+func TestUnimplementedCommandsFail(t *testing.T) {
+	t.Setenv("OSSIE_PLUGIN_DIR", t.TempDir())
+
+	tests := [][]string{
+		{"validate", "model.yaml"},
+		{"convert", "--from", "dbt", "--input", "model.yaml"},
+		{"plugin", "install", "dbt"},
+		{"plugin", "remove", "dbt"},
+	}
+
+	for _, args := range tests {
+		t.Run(strings.Join(args, " "), func(t *testing.T) {
+			t.Cleanup(func() { clearFlags(rootCmd) })
+
+			out := new(bytes.Buffer)
+			rootCmd.SetOut(out)
+			rootCmd.SetErr(out)
+			rootCmd.SetArgs(args)
+
+			err := rootCmd.Execute()
+			if err == nil {
+				t.Fatalf("Execute(%q) returned nil, want not-implemented error", args)
+			}
+			if !strings.Contains(err.Error(), "not yet implemented") {
+				t.Errorf("Execute(%q) error = %q, want it to mention not yet implemented", args, err)
+			}
+			if strings.Contains(out.String(), "Usage:") {
+				t.Errorf("Execute(%q) printed usage:\n%s", args, out.String())
+			}
+		})
+	}
+}
+
+// Flag values set by one Execute call stay on the shared rootCmd tree.
+func clearFlags(cmd *cobra.Command) {
+	cmd.Flags().Visit(func(f *pflag.Flag) {
+		_ = f.Value.Set(f.DefValue)
+		f.Changed = false
+	})
+	for _, sub := range cmd.Commands() {
+		clearFlags(sub)
+	}
+}
diff --git a/cli/cmd/validate.go b/cli/cmd/validate.go
index 08a3be55..0d096e60 100644
--- a/cli/cmd/validate.go
+++ b/cli/cmd/validate.go
@@ -35,6 +35,6 @@ func init() {
 }
 
 func runValidate(cmd *cobra.Command, args []string) error {
-	fmt.Fprintln(cmd.OutOrStdout(), "not yet implemented")
-	return nil
+	cmd.SilenceUsage = true
+	return fmt.Errorf("%s is not yet implemented", cmd.CommandPath())
 }