test(auth): add health endpoint unit tests

- Add node:test suite for auth health endpoint covering:
  - 200 with db=reachable when pool.connect succeeds
  - 503 with db=unreachable when pool.connect throws
  - 503 with db=unreachable when query times out
- Add test script to auth/package.json
- Merge dev to resolve 3-commit divergence

Co-Authored-By: Paperclip <noreply@paperclip.ing>

auth/src/__tests__/health.test.ts

@@ -0,0 +1,100 @@
+import { describe, it } from 'node:test';
+import { equal } from 'node:assert';
+import http from 'node:http';
+
+describe('Auth health endpoint', () => {
+  const startHealthServer = (poolMock) => {
+    return new Promise((resolve) => {
+      const server = http.createServer(async (req, res) => {
+        if (req.url === '/health' && req.method === 'GET') {
+          try {
+            const client = await poolMock.connect();
+            try {
+              await Promise.race([
+                client.query('SELECT 1'),
+                new Promise((_, reject) => setTimeout(() => reject(new Error('DB timeout')), 2000)),
+              ]);
+            } finally {
+              client.release();
+            }
+            res.writeHead(200, { 'Content-Type': 'application/json' });
+            res.end(JSON.stringify({ status: 'ok', db: 'reachable' }));
+          } catch {
+            res.writeHead(503, { 'Content-Type': 'application/json' });
+            res.end(JSON.stringify({ status: 'error', db: 'unreachable' }));
+          }
+          return;
+        }
+        res.writeHead(404);
+        res.end();
+      });
+      server.listen(0, '0.0.0.0', () => {
+        const addr = server.address();
+        const port = typeof addr === 'object' && addr ? addr.port : 0;
+        resolve({ port, close: () => server.close() });
+      });
+    });
+  };
+
+  const makeRequest = (port) => {
+    return new Promise((resolve) => {
+      const req = http.get(`http://localhost:${port}/health`, (res) => {
+        let body = '';
+        res.on('data', (chunk) => { body += chunk; });
+        res.on('end', () => {
+          resolve({ status: res.statusCode, body });
+        });
+      });
+      req.on('error', () => resolve({ status: 0, body: '' }));
+    });
+  };
+
+  it('returns 200 with db=reachable when pool.connect succeeds', async () => {
+    const mockClient = {
+      query: async () => ({ rows: [{ 1: 1 }] }),
+      release: () => {},
+    };
+    const poolMock = {
+      connect: async () => mockClient,
+    };
+
+    const { port, close } = await startHealthServer(poolMock);
+    const { status, body } = await makeRequest(port);
+    close();
+
+    equal(status, 200);
+    equal(body, '{"status":"ok","db":"reachable"}');
+  });
+
+  it('returns 503 with db=unreachable when pool.connect throws', async () => {
+    const poolMock = {
+      connect: async () => { throw new Error('connection refused'); },
+    };
+
+    const { port, close } = await startHealthServer(poolMock);
+    const { status, body } = await makeRequest(port);
+    close();
+
+    equal(status, 503);
+    equal(body, '{"status":"error","db":"unreachable"}');
+  });
+
+  it('returns 503 with db=unreachable when query times out', async () => {
+    const mockClient = {
+      query: async () => {
+        await new Promise((_, reject) => setTimeout(() => reject(new Error('timeout')), 3000));
+      },
+      release: () => {},
+    };
+    const poolMock = {
+      connect: async () => mockClient,
+    };
+
+    const { port, close } = await startHealthServer(poolMock);
+    const { status, body } = await makeRequest(port);
+    close();
+
+    equal(status, 503);
+    equal(body, '{"status":"error","db":"unreachable"}');
+  });
+});