fix(mock): native fetch bypasses MockAgent due to allowH2

lib/mock/mock-agent.js

@@ -87,6 +87,10 @@ class MockAgent extends Dispatcher {
       dispatchOpts.path = `${path}?${normalizedSearchParams}`
     }
 
+    if (dispatchOpts.allowH2 === false) {
+      delete dispatchOpts.allowH2
+    }
+
     return this[kAgent].dispatch(dispatchOpts, handler)
   }
 

test/issue-5036.js

@@ -0,0 +1,30 @@
+'use strict'
+
+const { test } = require('node:test')
+const assert = require('node:assert')
+const { MockAgent, setGlobalDispatcher } = require('../index.js')
+
+test('MockAgent works with native Node.js fetch', async (t) => {
+  // Only run if native fetch is available
+  if (typeof globalThis.fetch !== 'function') {
+    return
+  }
+
+  const agent = new MockAgent()
+  agent.disableNetConnect()
+
+  setGlobalDispatcher(agent)
+
+  agent.get('https://example.com')
+    .intercept({
+      method: 'GET',
+      path: '/v1/test'
+    })
+    .reply(200, { test: 123 })
+
+  const req = await globalThis.fetch('https://example.com/v1/test')
+  assert.strictEqual(req.status, 200)
+
+  const data = await req.json()
+  assert.deepStrictEqual(data, { test: 123 })
+})