Increase unit test coverage

[annevk]

It's not quite 100% and that might be good.

[foolip]

Running npm run coverage, it looks like coverage is 100% in 4 files out of 7 in lib/:

----------------------|----------|----------|----------|----------|-------------------|
File                  |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------------------|----------|----------|----------|----------|-------------------|
All files             |      100 |      100 |      100 |      100 |                   |
 get-user-status.js   |      100 |      100 |      100 |      100 |                   |
 pr-webhook.js        |      100 |      100 |      100 |      100 |                   |
 process-agreement.js |      100 |      100 |      100 |      100 |                   |
 update-pr.js         |      100 |      100 |      100 |      100 |                   |
----------------------|----------|----------|----------|----------|-------------------|

Not covered at all, seemingly, are add-data.js, app.js and routes.js.