Fix moving average test for discrete derivative sensor (#31750)

* fix test_data_moving_average_for_discrete_sensor

After https://github.com/home-assistant/home-assistant/pull/31717 the test
didn't actually test anything anymore.

This fixes that.

* make the test faster

tests/components/derivative/test_sensor.py

@@ -124,18 +124,18 @@ async def test_dataSet6(hass):
 async def test_data_moving_average_for_discrete_sensor(hass):
     """Test derivative sensor state."""
     # We simulate the following situation:
-    # The temperature rises 1 °C per minute for 1 hour long.
-    # There is a data point every second, however, the sensor returns
+    # The temperature rises 1 °C per minute for 30 minutes long.
+    # There is a data point every 30 seconds, however, the sensor returns
     # the temperature rounded down to an integer value.
     # We use a time window of 10 minutes and therefore we can expect
     # (because the true derivative is 1 °C/min) an error of less than 10%.
 
     temperature_values = []
-    for temperature in range(6):
-        temperature_values += [temperature] * 6
+    for temperature in range(30):
+        temperature_values += [temperature] * 2  # two values per minute
     time_window = 600
+    times = list(range(0, 1800 + 30, 30))
 
-    times = list(range(len(temperature_values)))
     config, entity_id = await _setup_sensor(
         hass, {"time_window": {"seconds": time_window}, "unit_time": "min", "round": 1}
     )  # two minute window
@@ -150,8 +150,8 @@ async def test_data_moving_average_for_discrete_sensor(hass):
             state = hass.states.get("sensor.power")
             derivative = round(float(state.state), config["sensor"]["round"])
             # Test that the error is never more than
-            # (time_window_in_minutes / true_derivative * 100) = 10%
-            assert abs(1 - derivative) <= 0.1
+            # (time_window_in_minutes / true_derivative * 100) = 10% + ε
+            assert abs(1 - derivative) <= 0.1 + 1e-6
 
 
 async def test_prefix(hass):