[LAB2] 312551098

[EusdenLin]

Description

At lab2, I write the main_test.js for the two main classes: mailsystem and application.
For mailsystem, I stub the mailsystem with a fake name and fake context to test the send/write functions.
For application, I create a fake name_list.txt for the getNames() function.
Check if the selected people are from the name list, the initialization about the application.
Finally, I mocked the send/write function in the mailsystem, making sure the notifySelected() function calls the selected people in the correct order and has no redundant calls.

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