After we run `require('mock-modules').dumpCache()`, the object exported by
the `emptyObject` module will no longer be identical to previously
exported objects, so tests like `expect(component.refs).toBe(emptyObject)`
will fail.
Note that this behavior only manifests itself in tests, because of course
we do not call `dumpCache` in production code.
We could consider storing the `emptyObject` globally to thwart the effects
of `dumpCache`, but it's more idiomatic simply to re-`require` the latest
version of `emptyObject`.
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