Need to add unit tests to the GPU-based spatial join

[pwrliang]

This PR #310 will implement the feature of GPU-based spatial join. We need unit tests for the library in Rust. #310 (comment)

[paleolimbot]

@pwrliang Can we close this? I believe there are Rust tests that were added in one of the PRs I reviewed for the rust wrapper crate.

[pwrliang]

Close this as the tests have been added in #586