The Angular.js bundle was evaluated a second time because a module that
required angular was proxyquire-d in session-test.js. When
`proxyquire(...)` loads a module, it does so with a fresh, empty module
cache [1] which is removed once the `proxyquire(...)` call returns.

As a result, every module that is transitively required by the
proxyquire'd module will be re-evaluated during the `proxyquire(...)`
call.

Aside from the performance cost for large modules, this is also bad for
any module which has side-effects as part of its evaluation. Angular
happens to detect this and abort when evaluated a second time.

The fix here is to use Angular's DI system to mock the only stubbed
dependencies instead of proxyquire.

[1] The _module cache_ is a (module ID/name => exports object) map.