Add test case for partial splitting.
Add test case for partial splitting.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=297425937

yext/closure-templates,google/closure-templates,yext/closure-templates,google/closure-templates,yext/closure-templates,google/closure-templates,google/closure-templates,yext/closure-templates,google/closure-templates