[noise] Add a session resume integration test

tests/integration/fixtures/api_noise_resume.yaml

@@ -0,0 +1,9 @@
+esphome:
+  name: host-noise-resume
+host:
+api:
+  encryption:
+    key: N4Yle5YirwZhPiHHsdZLdOA73ndj/84veVaLhTvxCuU=
+# VERY_VERBOSE so the frame helper logs "Session resumed!"
+logger:
+  level: VERY_VERBOSE

tests/integration/test_api_noise_resume.py

@@ -0,0 +1,46 @@
+"""Integration test for noise session resume."""
+
+from __future__ import annotations
+
+import aioesphomeapi.core
+import pytest
+
+from .types import APIClientConnectedFactory, RunCompiledFunction
+
+NOISE_KEY = "N4Yle5YirwZhPiHHsdZLdOA73ndj/84veVaLhTvxCuU="
+
+
+@pytest.mark.asyncio
+async def test_api_noise_resume(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected: APIClientConnectedFactory,
+) -> None:
+    """A reconnect with the ticket from the first connection resumes the session."""
+    if not hasattr(aioesphomeapi.core, "ResumeAPIError"):
+        pytest.skip("aioesphomeapi without noise session resume")
+
+    device_lines: list[str] = []
+
+    async with (
+        run_compiled(yaml_config, line_callback=device_lines.append),
+        api_client_connected(noise_psk=NOISE_KEY) as client,
+    ):
+        # First connection: full handshake, the device issues a ticket
+        info = await client.device_info()
+        assert info.name == "host-noise-resume"
+        assert not any("Session resumed" in line for line in device_lines)
+
+        # Same client reconnects and offers the ticket
+        await client.disconnect()
+        await client.connect(login=True)
+        info = await client.device_info()
+        assert info.name == "host-noise-resume"
+        assert any("Session resumed" in line for line in device_lines)
+
+        # The resumed session issued a fresh ticket, so it resumes again
+        await client.disconnect()
+        await client.connect(login=True)
+        info = await client.device_info()
+        assert info.name == "host-noise-resume"
+        assert sum("Session resumed" in line for line in device_lines) == 2