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Testing Power Monitoring System Integration in OpenPilot

A comprehensive test suite for power monitoring functionality in the OpenPilot system, focusing on battery management, charging behavior, and shutdown conditions. The tests verify power usage calculations, battery capacity tracking, and various safety conditions for vehicle power management.

Test Coverage Overview

The test suite provides extensive coverage of power monitoring scenarios in OpenPilot:

Battery capacity tracking and integration
Power usage calculations during charging and discharging
Voltage-based shutdown conditions
Ignition state handling
Power-down policy enforcement

Edge cases include boundary conditions for battery capacity limits and voltage thresholds.

Implementation Analysis

The testing approach utilizes pytest fixtures and mocking to simulate hardware interactions and time progression. The implementation employs systematic validation of power monitoring calculations using mock time and voltage values, with precise mathematical verification of expected outcomes against actual results.

Technical Details

Testing tools and configuration:

pytest framework with fixture support
Mock objects for hardware interfaces
Time simulation utilities
Parameterized voltage and power draw values
Mathematical validation of power calculations

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Comprehensive mock usage for hardware dependencies
Precise numerical comparisons with tolerance ranges
Systematic test case organization
Clear separation of test scenarios
Thorough edge case coverage

commaai/openpilot

system/hardware/tests/test_power_monitoring.py

            
import pytest

from openpilot.common.params import Params
from openpilot.system.hardware.power_monitoring import PowerMonitoring, CAR_BATTERY_CAPACITY_uWh, \
                                                CAR_CHARGING_RATE_W, VBATT_PAUSE_CHARGING, DELAY_SHUTDOWN_TIME_S

# Create fake time
ssb = 0.
def mock_time_monotonic():
  global ssb
  ssb += 1.
  return ssb

TEST_DURATION_S = 50
GOOD_VOLTAGE = 12 * 1e3
VOLTAGE_BELOW_PAUSE_CHARGING = (VBATT_PAUSE_CHARGING - 1) * 1e3

def pm_patch(mocker, name, value, constant=False):
  if constant:
    mocker.patch(f"openpilot.system.hardware.power_monitoring.{name}", value)
  else:
    mocker.patch(f"openpilot.system.hardware.power_monitoring.{name}", return_value=value)


@pytest.fixture(autouse=True)
def mock_time(mocker):
  mocker.patch("time.monotonic", mock_time_monotonic)


class TestPowerMonitoring:
  def setup_method(self):
    self.params = Params()

  # Test to see that it doesn't do anything when pandaState is None
  def test_panda_state_present(self):
    pm = PowerMonitoring()
    for _ in range(10):
      pm.calculate(None, None)
    assert pm.get_power_used() == 0
    assert pm.get_car_battery_capacity() == (CAR_BATTERY_CAPACITY_uWh / 10)

  # Test to see that it doesn't integrate offroad when ignition is True
  def test_offroad_ignition(self):
    pm = PowerMonitoring()
    for _ in range(10):
      pm.calculate(GOOD_VOLTAGE, True)
    assert pm.get_power_used() == 0

  # Test to see that it integrates with discharging battery
  def test_offroad_integration_discharging(self, mocker):
    POWER_DRAW = 4
    pm_patch(mocker, "HARDWARE.get_current_power_draw", POWER_DRAW)
    pm = PowerMonitoring()
    for _ in range(TEST_DURATION_S + 1):
      pm.calculate(GOOD_VOLTAGE, False)
    expected_power_usage = ((TEST_DURATION_S/3600) * POWER_DRAW * 1e6)
    assert abs(pm.get_power_used() - expected_power_usage) < 10

  # Test to check positive integration of car_battery_capacity
  def test_car_battery_integration_onroad(self, mocker):
    POWER_DRAW = 4
    pm_patch(mocker, "HARDWARE.get_current_power_draw", POWER_DRAW)
    pm = PowerMonitoring()
    pm.car_battery_capacity_uWh = 0
    for _ in range(TEST_DURATION_S + 1):
      pm.calculate(GOOD_VOLTAGE, True)
    expected_capacity = ((TEST_DURATION_S/3600) * CAR_CHARGING_RATE_W * 1e6)
    assert abs(pm.get_car_battery_capacity() - expected_capacity) < 10

  # Test to check positive integration upper limit
  def test_car_battery_integration_upper_limit(self, mocker):
    POWER_DRAW = 4
    pm_patch(mocker, "HARDWARE.get_current_power_draw", POWER_DRAW)
    pm = PowerMonitoring()
    pm.car_battery_capacity_uWh = CAR_BATTERY_CAPACITY_uWh - 1000
    for _ in range(TEST_DURATION_S + 1):
      pm.calculate(GOOD_VOLTAGE, True)
    estimated_capacity = CAR_BATTERY_CAPACITY_uWh + (CAR_CHARGING_RATE_W / 3600 * 1e6)
    assert abs(pm.get_car_battery_capacity() - estimated_capacity) < 10

  # Test to check negative integration of car_battery_capacity
  def test_car_battery_integration_offroad(self, mocker):
    POWER_DRAW = 4
    pm_patch(mocker, "HARDWARE.get_current_power_draw", POWER_DRAW)
    pm = PowerMonitoring()
    pm.car_battery_capacity_uWh = CAR_BATTERY_CAPACITY_uWh
    for _ in range(TEST_DURATION_S + 1):
      pm.calculate(GOOD_VOLTAGE, False)
    expected_capacity = CAR_BATTERY_CAPACITY_uWh - ((TEST_DURATION_S/3600) * POWER_DRAW * 1e6)
    assert abs(pm.get_car_battery_capacity() - expected_capacity) < 10

  # Test to check negative integration lower limit
  def test_car_battery_integration_lower_limit(self, mocker):
    POWER_DRAW = 4
    pm_patch(mocker, "HARDWARE.get_current_power_draw", POWER_DRAW)
    pm = PowerMonitoring()
    pm.car_battery_capacity_uWh = 1000
    for _ in range(TEST_DURATION_S + 1):
      pm.calculate(GOOD_VOLTAGE, False)
    estimated_capacity = 0 - ((1/3600) * POWER_DRAW * 1e6)
    assert abs(pm.get_car_battery_capacity() - estimated_capacity) < 10

  # Test to check policy of stopping charging after MAX_TIME_OFFROAD_S
  def test_max_time_offroad(self, mocker):
    MOCKED_MAX_OFFROAD_TIME = 3600
    POWER_DRAW = 0 # To stop shutting down for other reasons
    pm_patch(mocker, "MAX_TIME_OFFROAD_S", MOCKED_MAX_OFFROAD_TIME, constant=True)
    pm_patch(mocker, "HARDWARE.get_current_power_draw", POWER_DRAW)
    pm = PowerMonitoring()
    pm.car_battery_capacity_uWh = CAR_BATTERY_CAPACITY_uWh
    start_time = ssb
    ignition = False
    while ssb <= start_time + MOCKED_MAX_OFFROAD_TIME:
      pm.calculate(GOOD_VOLTAGE, ignition)
      if (ssb - start_time) % 1000 == 0 and ssb < start_time + MOCKED_MAX_OFFROAD_TIME:
        assert not pm.should_shutdown(ignition, True, start_time, False)
    assert pm.should_shutdown(ignition, True, start_time, False)

  def test_car_voltage(self, mocker):
    POWER_DRAW = 0 # To stop shutting down for other reasons
    TEST_TIME = 350
    VOLTAGE_SHUTDOWN_MIN_OFFROAD_TIME_S = 50
    pm_patch(mocker, "VOLTAGE_SHUTDOWN_MIN_OFFROAD_TIME_S", VOLTAGE_SHUTDOWN_MIN_OFFROAD_TIME_S, constant=True)
    pm_patch(mocker, "HARDWARE.get_current_power_draw", POWER_DRAW)
    pm = PowerMonitoring()
    pm.car_battery_capacity_uWh = CAR_BATTERY_CAPACITY_uWh
    ignition = False
    start_time = ssb
    for i in range(TEST_TIME):
      pm.calculate(VOLTAGE_BELOW_PAUSE_CHARGING, ignition)
      if i % 10 == 0:
        assert pm.should_shutdown(ignition, True, start_time, True) == \
                          (pm.car_voltage_mV < VBATT_PAUSE_CHARGING * 1e3 and \
                          (ssb - start_time) > VOLTAGE_SHUTDOWN_MIN_OFFROAD_TIME_S and \
                            (ssb - start_time) > DELAY_SHUTDOWN_TIME_S)
    assert pm.should_shutdown(ignition, True, start_time, True)

  # Test to check policy of not stopping charging when DisablePowerDown is set
  def test_disable_power_down(self, mocker):
    POWER_DRAW = 0 # To stop shutting down for other reasons
    TEST_TIME = 100
    self.params.put_bool("DisablePowerDown", True)
    pm_patch(mocker, "HARDWARE.get_current_power_draw", POWER_DRAW)
    pm = PowerMonitoring()
    pm.car_battery_capacity_uWh = CAR_BATTERY_CAPACITY_uWh
    ignition = False
    for i in range(TEST_TIME):
      pm.calculate(VOLTAGE_BELOW_PAUSE_CHARGING, ignition)
      if i % 10 == 0:
        assert not pm.should_shutdown(ignition, True, ssb, False)
    assert not pm.should_shutdown(ignition, True, ssb, False)

  # Test to check policy of not stopping charging when ignition
  def test_ignition(self, mocker):
    POWER_DRAW = 0 # To stop shutting down for other reasons
    TEST_TIME = 100
    pm_patch(mocker, "HARDWARE.get_current_power_draw", POWER_DRAW)
    pm = PowerMonitoring()
    pm.car_battery_capacity_uWh = CAR_BATTERY_CAPACITY_uWh
    ignition = True
    for i in range(TEST_TIME):
      pm.calculate(VOLTAGE_BELOW_PAUSE_CHARGING, ignition)
      if i % 10 == 0:
        assert not pm.should_shutdown(ignition, True, ssb, False)
    assert not pm.should_shutdown(ignition, True, ssb, False)

  # Test to check policy of not stopping charging when harness is not connected
  def test_harness_connection(self, mocker):
    POWER_DRAW = 0 # To stop shutting down for other reasons
    TEST_TIME = 100
    pm_patch(mocker, "HARDWARE.get_current_power_draw", POWER_DRAW)
    pm = PowerMonitoring()
    pm.car_battery_capacity_uWh = CAR_BATTERY_CAPACITY_uWh

    ignition = False
    for i in range(TEST_TIME):
      pm.calculate(VOLTAGE_BELOW_PAUSE_CHARGING, ignition)
      if i % 10 == 0:
        assert not pm.should_shutdown(ignition, False, ssb, False)
    assert not pm.should_shutdown(ignition, False, ssb, False)

  def test_delay_shutdown_time(self):
    pm = PowerMonitoring()
    pm.car_battery_capacity_uWh = 0
    ignition = False
    in_car = True
    offroad_timestamp = ssb
    started_seen = True
    pm.calculate(VOLTAGE_BELOW_PAUSE_CHARGING, ignition)

    while ssb < offroad_timestamp + DELAY_SHUTDOWN_TIME_S:
      assert not pm.should_shutdown(ignition, in_car,
                                          offroad_timestamp,
                                          started_seen), \
                       f"Should not shutdown before {DELAY_SHUTDOWN_TIME_S} seconds offroad time"
    assert pm.should_shutdown(ignition, in_car,
                                       offroad_timestamp,
                                       started_seen), \
                    f"Should shutdown after {DELAY_SHUTDOWN_TIME_S} seconds offroad time"