tests: Fix vidgrind test compilation errors

[Trek Hopton]

At the moment vidgrind tests are broken and do not compile. This needs to be fixed and we should be running circleci so that it doesn’t keep happening.

[kortschak]

I'm looking into this at the moment and it looks like a bit of a mess; a number of values/types in video_test.go are no longer exported from their defining packages or have undergone a major refactoring that is not obviously mappable back to the code that exists here.

I have a fix though.

[Trek Hopton]

Resolved in PR #114