fix xmrig pause

tests/xmrig-auto-pause.nix

@@ -0,0 +1,121 @@
+{
+  pkgs,
+  ...
+}:
+let
+  script = ../services/xmrig-auto-pause.py;
+  python = pkgs.python3;
+in
+pkgs.testers.runNixOSTest {
+  name = "xmrig-auto-pause";
+
+  nodes.machine =
+    { pkgs, ... }:
+    {
+      environment.systemPackages = [
+        pkgs.python3
+        pkgs.procps
+      ];
+
+      # Mock xmrig as a nice'd sleep process that can be stopped/started.
+      systemd.services.xmrig = {
+        description = "Mock xmrig miner";
+        serviceConfig = {
+          ExecStart = "${pkgs.coreutils}/bin/sleep infinity";
+          Type = "simple";
+          Nice = 19;
+        };
+        wantedBy = [ "multi-user.target" ];
+      };
+    };
+
+  testScript = ''
+    import time
+
+    PYTHON = "${python}/bin/python3"
+    SCRIPT = "${script}"
+
+    # Tuned for test VMs (1-2 cores).
+    # POLL_INTERVAL=1 keeps detection latency low.
+    # GRACE_PERIOD=5 is long enough to verify "stays stopped" but short
+    # enough that the full test completes in reasonable time.
+    # CPU_THRESHOLD=10 catches a single busy-loop on a 1-2 core VM.
+    POLL_INTERVAL = "1"
+    GRACE_PERIOD = "5"
+    CPU_THRESHOLD = "10"
+
+    def start_cpu_load(name):
+        """Start a non-nice CPU burn as a transient systemd unit."""
+        machine.succeed(
+            f"systemd-run --unit={name} --property=Type=exec "
+            f"bash -c 'while true; do :; done'"
+        )
+
+    def stop_cpu_load(name):
+        machine.succeed(f"systemctl stop {name}")
+
+    start_all()
+    machine.wait_for_unit("multi-user.target")
+    machine.wait_for_unit("xmrig.service")
+
+    with subtest("Start auto-pause monitor"):
+        machine.succeed(
+            f"systemd-run --unit=xmrig-auto-pause "
+            f"--setenv=POLL_INTERVAL={POLL_INTERVAL} "
+            f"--setenv=GRACE_PERIOD={GRACE_PERIOD} "
+            f"--setenv=CPU_THRESHOLD={CPU_THRESHOLD} "
+            f"{PYTHON} {SCRIPT}"
+        )
+        # Monitor needs two consecutive polls to compute a CPU delta.
+        time.sleep(3)
+
+    with subtest("xmrig stays running while system is idle"):
+        machine.succeed("systemctl is-active xmrig")
+
+    with subtest("xmrig stopped when CPU load appears"):
+        start_cpu_load("cpu-load")
+        machine.wait_until_fails("systemctl is-active xmrig", timeout=20)
+
+    with subtest("xmrig remains stopped during grace period after load ends"):
+        stop_cpu_load("cpu-load")
+        # Load just stopped. Grace period is 5s. Check at 2s — well within.
+        time.sleep(2)
+        machine.fail("systemctl is-active xmrig")
+
+    with subtest("xmrig resumes after grace period expires"):
+        # Already idle since previous subtest. Grace period (5s) plus
+        # detection delay (~2 polls) means xmrig should restart within ~8s.
+        machine.wait_until_succeeds("systemctl is-active xmrig", timeout=15)
+
+    with subtest("Intermittent load does not cause flapping"):
+        # First load — stop xmrig
+        start_cpu_load("cpu-load-1")
+        machine.wait_until_fails("systemctl is-active xmrig", timeout=20)
+        stop_cpu_load("cpu-load-1")
+
+        # Brief idle gap — shorter than grace period
+        time.sleep(2)
+
+        # Second load arrives before grace period expires
+        start_cpu_load("cpu-load-2")
+        time.sleep(3)
+
+        # xmrig must still be stopped
+        machine.fail("systemctl is-active xmrig")
+
+        stop_cpu_load("cpu-load-2")
+        machine.wait_until_succeeds("systemctl is-active xmrig", timeout=15)
+
+    with subtest("Sustained load keeps xmrig stopped"):
+        start_cpu_load("cpu-load-3")
+        machine.wait_until_fails("systemctl is-active xmrig", timeout=20)
+
+        # Stay busy longer than the grace period to prove continuous
+        # activity keeps xmrig stopped indefinitely.
+        time.sleep(8)
+        machine.fail("systemctl is-active xmrig")
+
+        stop_cpu_load("cpu-load-3")
+        machine.wait_until_succeeds("systemctl is-active xmrig", timeout=15)
+  '';
+}