Add test for embedded nfsiostat (DataDog#23280)

Author: sarah-witt

nfsstat/tests/common.py

@@ -19,10 +19,17 @@
     'start_commands': [
         'apt-get update',
         'apt-get install -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" -y docker.io',
+        # Remove default binary to ensure the check uses the embedded one
+        'rm -f /usr/local/sbin/nfsiostat',
     ],
     'docker_volumes': ['/var/run/docker.sock:/var/run/docker.sock'],
 }
 
+CONFIG_BUNDLED_BINARY = {
+    "init_config": {},
+    "instances": [{}],
+}
+
 METRICS = [
     'system.nfs.ops',
     'system.nfs.rpc_bklog',

nfsstat/tests/test_e2e.py

@@ -5,7 +5,7 @@
 
 from datadog_checks.dev.utils import get_metadata_metrics
 
-from .common import CONFIG, METRICS
+from .common import CONFIG, CONFIG_BUNDLED_BINARY, METRICS
 
 
 @pytest.mark.e2e
@@ -17,3 +17,11 @@ def test_e2e(dd_agent_check):
 
     aggregator.assert_all_metrics_covered()
     aggregator.assert_metrics_using_metadata(get_metadata_metrics())
+
+
+@pytest.mark.e2e
+def test_e2e_bundled_binary_no_mounts(dd_agent_check):
+    """Verify the agent's bundled nfsiostat binary exists and the check handles no NFS mounts gracefully."""
+    aggregator = dd_agent_check(CONFIG_BUNDLED_BINARY)
+
+    aggregator.assert_all_metrics_covered()