Add time-machine support for faster time freezing in tests (#2555)

Author: koxudaxi

pyproject.toml

@@ -88,7 +88,8 @@ test = [
   "pytest-cov>=5",
   "pytest-mock>=3.14",
   "pytest-xdist>=3.3.1",
-  "setuptools; python_version<'3.10'", # PyCharm debugger needs it
+  "setuptools; python_version<'3.10'",         # PyCharm debugger needs it
+  "time-machine>=3.1; python_version>='3.10'",
   { include-group = "coverage" },
 ]
 type = [

tests/conftest.py

@@ -3,7 +3,8 @@
 from __future__ import annotations
 
 import inspect
-from typing import TYPE_CHECKING, Protocol
+import sys
+from typing import TYPE_CHECKING, Any, Protocol
 
 import pytest
 from inline_snapshot import external_file, register_format_alias
@@ -14,6 +15,37 @@
     from collections.abc import Callable
     from pathlib import Path
 
+if sys.version_info >= (3, 10):
+    from datetime import datetime, timezone
+
+    import time_machine
+
+    def _parse_time_string(time_str: str) -> datetime:
+        """Parse time string to datetime with UTC timezone."""
+        for fmt in (
+            "%Y-%m-%dT%H:%M:%S%z",
+            "%Y-%m-%d %H:%M:%S%z",
+            "%Y-%m-%dT%H:%M:%S",
+            "%Y-%m-%d %H:%M:%S",
+            "%Y-%m-%d",
+        ):
+            try:
+                dt = datetime.strptime(time_str, fmt)  # noqa: DTZ007
+                if dt.tzinfo is None:
+                    dt = dt.replace(tzinfo=timezone.utc)
+                return dt  # noqa: TRY300
+            except ValueError:  # noqa: PERF203
+                continue
+        return datetime.fromisoformat(time_str.replace("Z", "+00:00"))  # pragma: no cover
+
+    def freeze_time(time_to_freeze: str, **kwargs: Any) -> time_machine.travel:  # noqa: ARG001
+        """Freeze time using time-machine (100-200x faster than freezegun)."""
+        dt = _parse_time_string(time_to_freeze)
+        return time_machine.travel(dt, tick=False)
+
+else:
+    from freezegun import freeze_time as freeze_time  # noqa: PLC0414
+
 
 def _normalize_line_endings(text: str) -> str:
     """Normalize line endings to LF for cross-platform comparison."""
@@ -200,3 +232,13 @@ def _inline_snapshot_file_formats() -> None:
 def min_version() -> str:
     """Return minimum Python version as string."""
     return f"3.{MIN_VERSION}"
+
+
+@pytest.fixture(scope="session", autouse=True)
+def _preload_heavy_modules() -> None:
+    """Pre-import heavy modules once per session to warm up the import cache.
+
+    This reduces per-test overhead when running with pytest-xdist,
+    as each worker only pays the import cost once at session start.
+    """
+    import datamodel_code_generator  # noqa: PLC0415, F401

tests/main/conftest.py

@@ -10,10 +10,9 @@
 from typing import Literal
 
 import pytest
-from freezegun import freeze_time
 
 from datamodel_code_generator.__main__ import Exit, main
-from tests.conftest import AssertFileContent, assert_directory_content, assert_output
+from tests.conftest import AssertFileContent, assert_directory_content, assert_output, freeze_time
 
 InputFileTypeLiteral = Literal["auto", "openapi", "jsonschema", "json", "yaml", "dict", "csv", "graphql"]
 CopyFilesMapping = Sequence[tuple[Path, Path]]

tests/main/jsonschema/test_main_jsonschema.py

@@ -10,7 +10,6 @@
 
 import black
 import pytest
-from freezegun import freeze_time
 from packaging import version
 
 from datamodel_code_generator import (
@@ -22,7 +21,7 @@
     generate,
 )
 from datamodel_code_generator.__main__ import Exit, main
-from tests.conftest import assert_directory_content
+from tests.conftest import assert_directory_content, freeze_time
 from tests.main.conftest import (
     DATA_PATH,
     JSON_SCHEMA_DATA_PATH,

tests/main/openapi/test_main_openapi.py

@@ -12,7 +12,6 @@
 import black
 import pydantic
 import pytest
-from freezegun import freeze_time
 from packaging import version
 
 from datamodel_code_generator import (
@@ -27,7 +26,7 @@
     inferred_message,
 )
 from datamodel_code_generator.__main__ import Exit
-from tests.conftest import assert_directory_content
+from tests.conftest import assert_directory_content, freeze_time
 from tests.main.conftest import (
     DATA_PATH,
     OPEN_API_DATA_PATH,

tests/main/test_main_general.py

@@ -6,7 +6,6 @@
 from typing import TYPE_CHECKING
 
 import pytest
-from freezegun import freeze_time
 
 from datamodel_code_generator import (
     DataModelType,
@@ -16,7 +15,7 @@
 )
 from datamodel_code_generator.__main__ import Config, Exit
 from datamodel_code_generator.format import PythonVersion
-from tests.conftest import create_assert_file_content
+from tests.conftest import create_assert_file_content, freeze_time
 from tests.main.conftest import (
     DATA_PATH,
     EXPECTED_MAIN_PATH,

tests/test_main_kr.py

@@ -7,11 +7,10 @@
 
 import black
 import pytest
-from freezegun import freeze_time
 
 from datamodel_code_generator import MIN_VERSION, chdir, inferred_message
 from datamodel_code_generator.__main__ import Exit
-from tests.conftest import create_assert_file_content
+from tests.conftest import create_assert_file_content, freeze_time
 from tests.main.conftest import run_main_and_assert, run_main_with_args
 
 DATA_PATH: Path = Path(__file__).parent / "data"