diff --git a/CLAUDE.md b/CLAUDE.md
index e11f550..2264f74 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -39,7 +39,8 @@ npm run dev
 
 ```
 quote-of-the-day-api/
-├── src/               # TypeScript source (to be created)
+├── src/               # TypeScript source
+│   └── placeholder.test.ts  # harness smoke test
 ├── dist/              # compiled output (git-ignored)
 ├── package.json
 ├── package-lock.json
diff --git a/src/placeholder.test.ts b/src/placeholder.test.ts
new file mode 100644
index 0000000..130e890
--- /dev/null
+++ b/src/placeholder.test.ts
@@ -0,0 +1,7 @@
+import { describe, it, expect } from 'vitest';
+
+describe('test harness', () => {
+  it('runs a passing test', () => {
+    expect(1 + 1).toBe(2);
+  });
+});