Code coverage improvement

[hoangnguyen92dn]

• It's great to see that you've included a few unit tests 👍  Could we increase the unit test coverage to cover most of the layers of application? It would be great to add a few instrumentation tests to the app as well.

• Would it be possible to set private access for those constants?
  

  survey-exam/domain/src/test/java/com/example/nimblesurveys/domain/usecase/LoginUseCaseTest.kt

  Lines 91 to 97 in 3ae3ac7

  	const val EMAIL = "[email protected]"
  	const val PASSWORD = "password"
  	const val ACCESS_TOKEN = "accesstoken"
  	const val REFRESH_TOKEN = "refreshtoken"
  	const val TOKEN_TYPE = "Bearer"
  	const val EXPIRY = 7200L
  	const val CREATED_AT = 1597169495L

[ryan-conway]

@hoangnguyen92dn noted on these, the constants should definitely be private