calibration: add test that triggers warning

lumicks/pylake/force_calibration/tests/test_power_spectrum_calibration.py

@@ -7,6 +7,7 @@
 import pytest
 
 from lumicks.pylake.force_calibration import power_spectrum_calibration as psc
+from lumicks.pylake.force_calibration.power_spectrum import PowerSpectrum
 from lumicks.pylake.force_calibration.calibration_models import (
     NoFilter,
     PassiveCalibrationModel,
@@ -60,6 +61,30 @@ def test_calibration_result():
         psc.CalibrationResults(invalid=5)
 
 
+def test_fit_warn():
+    # fmt:off
+    power = [
+        1.64129e-04, 1.43886e-05, 7.34803e-06, 7.23357e-06, 6.01199e-06, 5.71373e-06, 6.20084e-06,
+        5.16348e-06, 5.61539e-06, 4.88627e-06, 5.21241e-06,
+    ]
+
+    frequency = [
+        1204.923, 3204.795, 5204.667, 7204.538, 9204.411, 11204.283, 13204.155, 15204.027,
+        17203.899, 19341.362, 21523.622,
+    ]
+    # fmt:on
+
+    ps = PowerSpectrum(np.arange(len(frequency)), 78125)
+    ps.power, ps.frequency = np.asarray(power), np.array(frequency)
+
+    psc.fit_power_spectrum(
+        ps,
+        PassiveCalibrationModel(1.0),
+        bias_correction=False,
+        loss_function="lorentzian",
+    )
+
+
 @pytest.mark.parametrize(
     "loss_function, corner_frequency,diffusion_constant,alpha,f_diode,num_samples,viscosity,bead_diameter,temperature",
     [