From f13bd3c4c6a44a4a3f5deb0d9fcaf7252c543fb4 Mon Sep 17 00:00:00 2001
From: Nathan Hangen <nhangen@gmail.com>
Date: Sun, 10 May 2026 21:34:15 -0400
Subject: [PATCH] test(mcp): assert documented bucket boundaries land in the
 Prom scrape

The existing bucket tests pinned the exported JS constants; the views[]
wiring in MeterProvider could be deleted and they would still pass. This
test boots a real exporter, makes one observation, and asserts every
documented boundary appears as an le= label on the bucket lines.
---
 gitnexus/test/unit/mcp/metrics.test.ts | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/gitnexus/test/unit/mcp/metrics.test.ts b/gitnexus/test/unit/mcp/metrics.test.ts
index 9c04ea0bf..e5e71c0d6 100644
--- a/gitnexus/test/unit/mcp/metrics.test.ts
+++ b/gitnexus/test/unit/mcp/metrics.test.ts
@@ -256,4 +256,28 @@ describe('bucket boundary contract', () => {
   it('publishes the documented result-size buckets verbatim', () => {
     expect(RESULT_BYTES_BUCKETS).toEqual([512, 2048, 8192, 32768, 131072, 524288, 2097152]);
   });
+
+  it('exposes the documented bucket boundaries in the Prometheus scrape', async () => {
+    process.env['GITNEXUS_OTEL_METRICS'] = 'on';
+    await withRandomPort(async () => {
+      const init = await initMetrics();
+      await observe(
+        'context',
+        async () => ({ content: [{ type: 'text', text: 'x' }] }),
+        (r) => Buffer.byteLength(r.content[0]!.text, 'utf8'),
+        () => false,
+      );
+      const text = await fetch(`http://127.0.0.1:${init.port}/metrics`).then((r) => r.text());
+      for (const b of DURATION_BUCKETS_SECONDS) {
+        expect(text).toMatch(
+          new RegExp(`gitnexus_mcp_tool_request_duration_seconds_bucket\\{[^}]*le="${b}"\\}`),
+        );
+      }
+      for (const b of RESULT_BYTES_BUCKETS) {
+        expect(text).toMatch(
+          new RegExp(`gitnexus_mcp_tool_result_bytes_bucket\\{[^}]*le="${b}"\\}`),
+        );
+      }
+    });
+  });
 });