Restore torch defaults between sgl-kernel tests (#11131)

sgl-kernel/tests/conftest.py

+import pytest
+import torch
+
+
+# This ensures the torch defaults don't get left in modified states between
+# tests (e.g., when a test fails before restoring the original value), which
+# can cause subsequent tests to fail.
+@pytest.fixture(autouse=True)
+def reset_torch_defaults():
+    orig_default_device = torch.get_default_device()
+    orig_default_dtype = torch.get_default_dtype()
+    yield
+    torch.set_default_dtype(orig_default_dtype)
+    torch.set_default_device(orig_default_device)

sgl-kernel/tests/test_torch_defaults_reset.py

+import pytest
+import torch
+
+
+def test_change_torch_defaults():
+    torch.set_default_device("cpu:0")
+    torch.set_default_dtype(torch.float16)
+
+
+def test_check_torch_defaults():
+    assert torch.get_default_device() == torch.device("cpu")
+    assert torch.get_default_dtype() == torch.float32
+
+
+if __name__ == "__main__":
+    pytest.main([__file__])