In an example. NoopTelemetry would be some type of empty class not dependent on mock (I've used a meta class a singleton in this case, but whichever, could be a module just the same). To test, you'd pass in a mock object to telemetry and check that a both timer_start and timer_stop are both called with the correct function name.

In your main or context, you setup your application with the needed pieces.

  def main():
     context = {'telemetry': StatsClient(....)}
     start(context)

  def start(context):
      algo_5(1, 4, context['telemetry'])

  def algo_5(param1, param2, telemetry=NoopTelemetry):
     telemetry.timer_start('algo_5')
     ret = param1 / param2 ** param2 # whatever
     telemetry.timer_stop('algo_5)
     return ret
  
  def test_start():
    context = {'telemetry': MagicMock()}
    start(context)
    # more testing.

  def test_algo5_math():
    ret = algo5(4, 5)
    assert 78  # maybe?

  def test_algo5_telemetry():
    mm = MagicMock()
    algo5(1, 1, mm)
    assert mm.timer_start.called_with_args(['algo5'])
    assert mm.timer_stop.called_with_args(['algo5'])