[Task] Add unit test cases for ChatHistoryService

[tjtanjin]

Task Description: Currently, we run unit tests using jest which can be found here.

However, the test cases are not yet comprehensive enough and work can be done to cover more grounds. Specifically for this issue, we hope to add test cases for the ChatHistoryService.

Deliverable(s): New unit test cases that cover the testing of the VoiceService.

Additional Context:

• The ChatHistoryService can be found here
• An example for AudioService can be found here which may serve as a good source for reference

[anjumnnit]

assign this to me I will complete it. @tjtanjin

[tjtanjin]

assign this to me I will complete it. @tjtanjin

Go for it!

[anjumnnit]

sorry I have unassigned this issue. U can assign it to other who can finish it early.