Added tests for the history_events.go

[agautam478]

What changed?

• Added a few cases for 3 methods in history_events.go file.

Why?
unit test coverage

How did you test it?
unit tests

Potential risks

Release notes

Documentation Changes

[coveralls]

Pull Request Test Coverage Report for Build 018f548f-0046-4edc-b745-69306b729571

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 67 unchanged lines in 10 files lost coverage.
• Overall coverage decreased (-0.02%) to 68.11%

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Files with Coverage Reduction	New Missed Lines	%
common/task/weighted_round_robin_task_scheduler.go	1	88.06%
tools/cli/admin_db_decode_thrift.go	1	71.79%
common/task/fifo_task_scheduler.go	2	85.57%
common/util.go	2	91.78%
service/matching/taskListManager.go	2	81.16%
service/history/execution/mutable_state_util.go	2	78.52%
common/persistence/historyManager.go	2	66.67%
service/history/task/fetcher.go	3	85.57%
service/history/task/task_util.go	20	70.57%
service/history/execution/mutable_state_task_refresher.go	32	56.65%

Totals
Change from base Build 018f5467-b337-442d-bcf0-8ad761c213c7:	-0.02%
Covered Lines:	100048
Relevant Lines:	146892

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💛 - Coveralls