Improve IGListWorkingRangeHandler Test Coverage
Improve IGListWorkingRangeHandler Test Coverage

Summary:
Added working range handler tests. This will allow changes/experiments to be made to the working range handler with improved confidence.

Two of the added tests are currently disabled; working range updates don't currently take inserts and deletes into account and so these tests fail.

Reviewed By: rnystrom

Differential Revision: D13717357

fbshipit-source-id: dd4523d3162cfe13ee03e9d10ffa22b58514ca5f

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