diff --git a/apps/web/src/sync.test.ts b/apps/web/src/sync.test.ts
index 9fb5216..f5294db 100644
--- a/apps/web/src/sync.test.ts
+++ b/apps/web/src/sync.test.ts
@@ -1,7 +1,13 @@
+import { readFile } from 'node:fs/promises'
+import { fileURLToPath } from 'node:url'
 import { describe, expect, it } from 'vitest'
 
 describe('sync contract', () => {
-  it('keeps capture independent from browser connectivity state', () => {
-    expect(typeof navigator === 'undefined' || typeof navigator.onLine === 'boolean').toBe(true)
+  it('does not treat browser connectivity state as proof that the API is reachable', async () => {
+    const source = await readFile(fileURLToPath(new URL('./sync.ts', import.meta.url)), 'utf8')
+
+    expect(source).not.toContain('navigator.onLine')
+    expect(source).toContain("window.addEventListener('online'")
+    expect(source).toContain("document.addEventListener('visibilitychange'")
   })
 })