fix(cli): improve no stacks found message in synth output

packages/cdktf-cli/src/bin/cmds/ui/synth.tsx

@@ -22,11 +22,16 @@ interface SynthConfig extends CommonSynthConfig {
 type SynthOutputConfig = {
   stacks: SynthesizedStack[];
 };
-const SynthOutput = ({ stacks }: SynthOutputConfig): React.ReactElement => {
+export const SynthOutput = ({
+  stacks,
+}: SynthOutputConfig): React.ReactElement => {
   return (
     <Text>
-      Generated Terraform code for the stacks:{" "}
-      {stacks?.map((s) => s.name).join(", ")}
+      {stacks?.length
+        ? `Generated Terraform code for the stacks: ${stacks
+            .map((s) => s.name)
+            .join(", ")}`
+        : "No stacks found in the configuration."}
     </Text>
   );
 };

packages/cdktf-cli/src/test/ui/synth.test.tsx

@@ -0,0 +1,27 @@
+/**
+ * Copyright (c) HashiCorp, Inc.
+ * SPDX-License-Identifier: MPL-2.0
+ */
+
+import React from "react";
+import { render } from "ink-testing-library";
+import { stripAnsi } from "../test-helper";
+import { SynthOutput } from "../../bin/cmds/ui/synth";
+import { SynthesizedStack } from "@cdktf/cli-core";
+
+test("SynthOutput shows message when no stacks are found", () => {
+  const { lastFrame } = render(<SynthOutput stacks={[]} />);
+  expect(stripAnsi(lastFrame())).toBe("No stacks found in the configuration.");
+});
+
+test("SynthOutput lists multiple stack names", () => {
+  const multipleStacks = [
+    { name: "stack1" },
+    { name: "stack2" },
+  ] as SynthesizedStack[];
+
+  const { lastFrame } = render(<SynthOutput stacks={multipleStacks} />);
+  expect(stripAnsi(lastFrame())).toBe(
+    "Generated Terraform code for the stacks: stack1, stack2",
+  );
+});