Add test_gitt_pulse_fit

pybop/applications/gitt_methods.py

@@ -47,7 +47,7 @@
         )
 
         # Define the cost to optimise
-        self.parameter_set = parameter_set
+        self.parameter_set = parameter_set.copy()
         self.model = pybop.lithium_ion.SPDiffusion(
             parameter_set=self.parameter_set, build=True
         )
@@ -92,14 +92,14 @@
         verbose: bool = False,
     ):
         # Preallocate outputs
         self.pulses = []
         stoichiometry = []
         diffusion_time = []
         series_resistance = []
 
         for pulse_index in gitt_pulse_index:
             # Estimate the parameters for this pulse
             self.pulses.append(
                 pybop.GITTPulseFit(
                     gitt_pulse=gitt_dataset.get_subset(pulse_index),
                     parameter_set=parameter_set,
@@ -110,16 +110,16 @@
             )
 
             # Log and update the parameter estimates for the next iteration
             parameter_set.update(
                 {
                     "Particle diffusion time scale [s]": self.pulses[-1].results.x[0],
                     "Series resistance [Ohm]": self.pulses[-1].results.x[1],
                 }
             )
             diffusion_time.append(parameter_set["Particle diffusion time scale [s]"])
             series_resistance.append(parameter_set["Series resistance [Ohm]"])
             stoichiometry.append(parameter_set["Initial stoichiometry"])
             parameter_set.update(
                 {
                     "Initial stoichiometry": stoichiometry[-1]
                     + (
@@ -130,7 +130,7 @@
                 }
             )
 
         self.parameter_data = pybop.Dataset(
             {
                 "Stoichiometry": np.asarray(stoichiometry),
                 "Particle diffusion time scale [s]": np.asarray(diffusion_time),

tests/integration/test_applications.py

@@ -2,6 +2,9 @@
 import pytest
 
 import pybop
+from pybop.models.lithium_ion.basic_SP_diffusion import (
+    convert_physical_to_electrode_parameters,
+)
 
 
 class TestApplications:
@@ -96,3 +99,46 @@ def test_stoichiometry_fit(self, parameter_set):
         np.testing.assert_allclose(
             ocv_fit.shift, 0.1 * nom_capacity, rtol=5e-3, atol=5e-3
         )
+
+    @pytest.fixture
+    def half_cell_model(self):
+        parameter_set = pybop.ParameterSet("Xu2019")
+        return pybop.lithium_ion.SPMe(
+            parameter_set=parameter_set, options={"working electrode": "positive"}
+        )
+
+    @pytest.fixture
+    def pulse_data(self, half_cell_model):
+        sigma = 1e-3
+        initial_state = {"Initial SoC": 0.9}
+        experiment = pybop.Experiment(
+            [
+                "Rest for 1 second",
+                "Discharge at 1C for 10 minutes (10 second period)",
+                "Rest for 20 minutes",
+            ]
+        )
+        values = half_cell_model.predict(
+            initial_state=initial_state, experiment=experiment
+        )
+        corrupt_values = values["Voltage [V]"].data + np.random.normal(
+            0, sigma, len(values["Voltage [V]"].data)
+        )
+        return pybop.Dataset(
+            {
+                "Time [s]": values["Time [s]"].data,
+                "Current function [A]": values["Current [A]"].data,
+                "Discharge capacity [A.h]": values["Discharge capacity [A.h]"].data,
+                "Voltage [V]": corrupt_values,
+            }
+        )
+
+    def test_gitt_pulse_fit(self, half_cell_model, pulse_data):
+        parameter_set = convert_physical_to_electrode_parameters(
+            half_cell_model.parameter_set, "positive"
+        )
+        diffusion_time = parameter_set["Particle diffusion time scale [s]"]
+
+        gitt_fit = pybop.GITTPulseFit(pulse_data, parameter_set)
+
+        np.testing.assert_allclose(gitt_fit.results.x[0], diffusion_time, rtol=5e-2)