Add E2E test for login

[fyliu]

Integration/E2E test:

• Write cypress test -- visit app, login, validate that you can see your name [Louis]
• Add cypress helper to auto login as different types of users (regular, admin, security admin) [Claire]
• valid login (Cypress automatically adds cookies in the browser) [Claire]
• invalid login with wrong password [Claire]

does not include unit tests anymore

[fyliu]

I had trouble mocking async code and tried jest/enzyme and react testing library. React testing library seems to do the trick. I still need to add the actual tests. This should be done by Wednesday if no other issues come up.

[nclairesays]

Cypress tests in progress. Adding edge cases for what happens during failed login attempts. Learning and figuring out the right architecture to writing these tests. Eta hopefully Wednesday also.

@fyliu you can try mocking out async calls using the nock library or using the act block in react testing library

[fyliu]

I checked that this works and the code looks good.