Add test for species transport model (#2280)

Test the following features of the species transport model:

- Turning on the species transport model
- Checking the mixtures object command list
- Creating a custom mixture with custom species (using the TUI)
- Copying an existing mixture
- Reassigning a cellzone material to a different mixture
- Deleting an existing mixture

This test should be updated as the settings API is expanded to cover all functionality pertaining to the species transport model.

tests/test_solvermode/test_species_model.py

@@ -0,0 +1,72 @@
+import pytest
+
+
+@pytest.mark.setup
+@pytest.mark.fluent_version(">=24.1")
+def test_change_create_mixture(load_mixing_elbow_mesh):
+    solver_session = load_mixing_elbow_mesh
+
+    # Test turning on species transport model
+    species_mdl = solver_session.setup.models.species.model
+
+    assert species_mdl.option() == "off"
+    species_mdl.option = "species-transport"
+    assert species_mdl.option() == "species-transport"
+
+    # Test command names list
+    materials = solver_session.setup.materials
+    assert sorted(materials.mixture.command_names) == sorted(
+        [
+            "delete",
+            "list",
+            "list_properties",
+            "make_a_copy",
+        ]
+    )
+
+    # Test change/creating a mixture with custom species from template
+    custom_species_1 = materials.fluid.create("custom-species-1")
+    custom_species_2 = materials.fluid.create("custom-species-2")
+    solver_session.tui.define.materials.change_create(
+        "mixture-template",  # Change/create mixture-template
+        "custom-mixture",  # Rename to `custom-mixture`
+        "yes",  # Change mixture species
+        "2",  # Set number of species to 2
+        custom_species_1.name(),  # Set species 1
+        custom_species_2.name(),  # Set species 2
+        "0",  # No surface species
+        "0",  # No site species
+        "no",  # Do not change density
+        "no",  # Do not change specific heat
+        "no",  # Do not change thermal conductivity
+        "no",  # Do not change viscosity
+        "no",  # Do not change mass diffusivity
+        "no",  # Do not change speed of sound
+        "yes",  # Overwrite mixture-template
+    )
+    assert "custom-mixture" in materials.mixture.keys()
+    assert "mixture-template" not in materials.mixture.keys()
+
+    # Test that mixture contains correct species
+    mix_species = solver_session.setup.materials.mixture[
+        "custom-mixture"
+    ].species.volumetric_species.keys()
+    assert "custom-species-1" in mix_species
+    assert "custom-species-2" in mix_species
+
+    # Test copying a mixture
+    materials.mixture.make_a_copy(
+        from_="custom-mixture",
+        to="custom-mixture-copy",
+    )
+    assert "custom-mixture-copy" in materials.mixture.keys()
+
+    # Test changing cellzone mixture
+    elbow_zone = solver_session.setup.cell_zone_conditions.fluid["elbow-fluid"]
+    assert elbow_zone.material() == "custom-mixture"
+    elbow_zone.material = "custom-mixture-copy"
+    assert elbow_zone.material() == "custom-mixture-copy"
+
+    # Test deleting a mixture
+    materials.mixture.delete(name_list=["custom-mixture"])
+    assert "custom-mixture" not in materials.mixture.keys()