test(cli): cover native allocator purge delay default

Author: kvlonge

tests/integration/src/sqlbuild/cli/commands/main/_test_types.py

@@ -809,3 +809,10 @@ class DiscoveryWorkTestCase:
     command: tuple[str, ...]
     expected_exit_code: int
     expected_eager_output_column_scans: int
+
+
+@dataclass(frozen=True)
+class NativeAllocatorEntryTestCase:
+    description: str
+    inherited_environment: tuple[tuple[str, str], ...]
+    expected_purge_delay: str

tests/integration/src/sqlbuild/cli/commands/main/test_native_allocator_entry.py

@@ -0,0 +1,75 @@
+"""Fresh-process integration coverage for the native allocator entrypoint default."""
+
+from __future__ import annotations
+
+import json
+import os
+import subprocess
+import sys
+
+import pytest
+
+from tests.integration.src.sqlbuild.cli.commands.main._test_types import (
+    NativeAllocatorEntryTestCase,
+)
+
+_PURGE_DELAY_VARIABLE: str = "MIMALLOC_PURGE_DELAY"
+_SCRIPT: str = """
+import json
+import os
+import sys
+from sqlbuild.cli.entry.main.entry import main
+
+loaded_at_import = "sqlbuild._native" in sys.modules
+exit_code = main(["--version"])
+print(json.dumps({
+    "loaded_at_import": loaded_at_import,
+    "loaded_after_main": "sqlbuild._native" in sys.modules,
+    "purge_delay": os.environ.get("MIMALLOC_PURGE_DELAY"),
+    "exit_code": exit_code,
+}))
+"""
+
+
+@pytest.mark.parametrize(
+    "test_case",
+    [
+        NativeAllocatorEntryTestCase(
+            description="unset purge delay defaults to ten milliseconds",
+            inherited_environment=(),
+            expected_purge_delay="10",
+        ),
+        NativeAllocatorEntryTestCase(
+            description="user purge delay is preserved",
+            inherited_environment=((_PURGE_DELAY_VARIABLE, "250"),),
+            expected_purge_delay="250",
+        ),
+    ],
+    ids=lambda case: case.description,
+)
+def test_given_fresh_process_when_running_cli_entry_then_purge_delay_is_set_before_native_load(
+    test_case: NativeAllocatorEntryTestCase,
+) -> None:
+    environment: dict[str, str] = os.environ.copy()
+    environment.pop(_PURGE_DELAY_VARIABLE, None)
+    environment.update(test_case.inherited_environment)
+
+    result: subprocess.CompletedProcess[str] = subprocess.run(
+        [sys.executable, "-c", _SCRIPT],
+        check=True,
+        capture_output=True,
+        env=environment,
+        text=True,
+    )
+    payload: dict[str, object] = json.loads(result.stdout.strip().splitlines()[-1])
+
+    assert payload == {
+        "loaded_at_import": False,
+        "loaded_after_main": True,
+        "purge_delay": test_case.expected_purge_delay,
+        "exit_code": 0,
+    }
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-vv"])