[WIP] Fix tests in this pull request

src/py/mat3ra/mode/method.py

@@ -9,6 +9,14 @@
 class Method(BaseMethod, InMemoryEntityPydantic):
     data: Dict[str, Any] = Field(default_factory=dict, exclude=True)
 
+    @classmethod
+    def get_default_config(cls) -> Dict[str, Any]:
+        """Return the default configuration for a Method."""
+        return {
+            "type": "pseudopotential",
+            "subtype": "us",
+        }
+
     def clone_without_data(self) -> "Method":
         cloned = self.clone()
         cloned.data = {}

src/py/mat3ra/mode/models/dft.py

@@ -1,8 +1,8 @@
-from typing import List, Union
+from typing import Any, List, Union
 
 from mat3ra.esse.models.core.primitive.slugified_entry import SlugifiedEntry
 from mat3ra.esse.models.model.mixins.dft.gga_functional import Functional
-from pydantic import Field
+from pydantic import Field, field_validator
 
 from ..model import Model
 
@@ -12,3 +12,35 @@ class DFTModel(Model):
     refiners: List[SlugifiedEntry] = Field(default_factory=list)
     modifiers: List[SlugifiedEntry] = Field(default_factory=list)
 
+    @field_validator("functional", mode="before")
+    @classmethod
+    def _coerce_functional(cls, value: Any) -> Union[SlugifiedEntry, None]:
+        """Convert string to SlugifiedEntry if needed."""
+        if value is None:
+            return None
+        if isinstance(value, SlugifiedEntry):
+            return value
+        if isinstance(value, str):
+            return SlugifiedEntry(name=value, slug=value)
+        if isinstance(value, dict):
+            return SlugifiedEntry(**value)
+        return value
+
+    @field_validator("refiners", "modifiers", mode="before")
+    @classmethod
+    def _coerce_list_of_entries(cls, value: Any) -> List[SlugifiedEntry]:
+        """Convert list of strings to list of SlugifiedEntry if needed."""
+        if not value:
+            return []
+        result = []
+        for item in value:
+            if isinstance(item, SlugifiedEntry):
+                result.append(item)
+            elif isinstance(item, str):
+                result.append(SlugifiedEntry(name=item, slug=item))
+            elif isinstance(item, dict):
+                result.append(SlugifiedEntry(**item))
+            else:
+                result.append(item)
+        return result
+