Add more test to reach 100% coverage for visibility_single_manager

[bowenxia]

What changed?
Add unit tests to reach 100% coverage for the file

Why?
code coverage week

How did you test it?
unit test

Potential risks

Release notes

Documentation Changes

[codecov]

Codecov Report

Merging #5832 (8daa448) into master (c56c124) will increase coverage by 0.24%.
Report is 1 commits behind head on master.
The diff coverage is n/a.

❗ Current head 8daa448 differs from pull request most recent head e08e72c. Consider uploading reports for the commit e08e72c to get more accurate results

Additional details and impacted files

see 8 files with indirect coverage changes

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[coveralls]

Pull Request Test Coverage Report for Build 018e9d46-51b7-469d-8c5a-6f1158cec0c9

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 38 unchanged lines in 9 files lost coverage.
• Overall coverage increased (+0.08%) to 65.422%

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Files with Coverage Reduction	New Missed Lines	%
service/history/task/transfer_standby_task_executor.go	2	86.6%
common/task/weighted_round_robin_task_scheduler.go	2	89.05%
common/persistence/sql/sqlplugin/postgres/task.go	2	73.4%
service/history/shard/context.go	2	66.7%
common/persistence/sql/sqlplugin/postgres/db.go	2	80.0%
service/history/execution/mutable_state_util.go	2	78.13%
common/asyncworkflow/queue/consumer/default_consumer.go	3	92.05%
service/history/task/fetcher.go	3	86.6%
service/history/task/task_util.go	20	70.57%

Totals
Change from base Build 018e9d44-8f40-49fc-a0a5-47b187356a25:	0.08%
Covered Lines:	95738
Relevant Lines:	146339

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💛 - Coveralls

[taylanisikdemir]

nit: this is already covered by other unit tests targeting public funcs. unless you wanted to cover specific edge cases, you don't need to add a separate test func targeting private funcs.

[bowenxia]

Yes, I am testing an edge case with an input is nil.