Speed up unit tests (#975)

Author: maddenp-cu

src/uwtools/config/jinja2.py

@@ -295,6 +295,8 @@ def _deref_render(val: str, context: dict, local: dict | None = None) -> str:
     :param local: Local sibling values to use if a match is not found in context.
     :return: The rendered value (potentially unchanged).
     """
+    if not any(marker in val for marker in ("{{", "{%", "{#")):
+        return val
     env = _register_filters(Environment(undefined=StrictUndefined))
     template = env.from_string(val)
     context = _update_context(context, local)

src/uwtools/tests/support.py

@@ -8,7 +8,7 @@
 if TYPE_CHECKING:
     from collections.abc import Callable
 
-import yaml
+import json
 
 from uwtools.config.validator import _validation_errors
 from uwtools.utils.file import resource_path
@@ -61,7 +61,7 @@ def schema_validator(schema_name: str, *args: Any) -> Callable:
     :returns: A lambda that, when called with an input to test, returns a string (possibly empty)
         containing the validation errors.
     """
-    schema = yaml.safe_load((resource_path("jsonschema") / f"{schema_name}.jsonschema").read_text())
+    schema = json.loads((resource_path("jsonschema") / f"{schema_name}.jsonschema").read_text())
     defs = schema.get("$defs", {})
     for arg in args:
         schema = schema[arg]