Adds test for relative path

Author: DrPaulSharp

tests/test_models.py

@@ -1,5 +1,6 @@
 """Test the pydantic models."""
 
+import pathlib
 import re
 from typing import Callable
 
@@ -100,6 +101,13 @@ def test_initialise_with_extra_fields(self, model: Callable, model_params: dict)
             model(new_field=1, **model_params)
 
 
+def test_custom_file_path_is_absolute() -> None:
+    """If we use provide a relative path to the custom file model, it should be converted to an absolute path."""
+    relative_path = pathlib.Path("./relative_path")
+    custom_file = RATapi.models.CustomFile(path=relative_path)
+    assert custom_file.path.is_absolute()
+
+
 def test_data_eq() -> None:
     """If we use the Data.__eq__ method with an object that is not a pydantic BaseModel, we should return
     "NotImplemented".