scripts: sysmon: add io metrics of processes

BUG=b:255782067
TEST=None

Change-Id: I8b87e8a357c0c48d5b1cf9326f29db84527a480a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4242822
Reviewed-by: Sergey Fetisov <sfetisov@google.com>
Commit-Queue: Congbin Guo <guocb@chromium.org>
Auto-Submit: Congbin Guo <guocb@chromium.org>
Tested-by: Congbin Guo <guocb@chromium.org>
diff --git a/scripts/sysmon/proc_metrics_unittest.py b/scripts/sysmon/proc_metrics_unittest.py
index ed1fbf6..5d58c2b 100644
--- a/scripts/sysmon/proc_metrics_unittest.py
+++ b/scripts/sysmon/proc_metrics_unittest.py
@@ -28,6 +28,14 @@
     proc.cpu_times.return_value.iowait = 12
     proc.cpu_times.return_value.children_system = 13
     proc.cpu_times.return_value.children_user = 14
+
+    proc.io_counters.return_value.read_count = 20
+    proc.io_counters.return_value.read_bytes = 21
+    proc.io_counters.return_value.read_chars = 22
+    proc.io_counters.return_value.write_count = 23
+    proc.io_counters.return_value.write_bytes = 24
+    proc.io_counters.return_value.write_chars = 25
+
     if parent is not None:
         proc.parent.return_value = parent
     return proc