exclusion of heavy/long/dependency requiring tests

[Dieterbe]

1. the tests in stacktest all require docker and docker-compose to run a stack. they also require make bin to have run.
2. idx/cassandra has a few Benchmarks that CreateSession and require a cassandra to be running.

these tests are:
A) time consuming to always run
B) not trivial to get the context right. For 2 we could probably just use docker also though, and any dependency can basically solved this way, so that only problem 1 remains.

As for how to exclude tests, there seem to be 2 common approaches:
a) build tags: see https://stackoverflow.com/questions/24030059/skip-some-tests-with-go-test and https://medium.com/@povilasve/go-advanced-tips-tricks-a872503ac859
b) env vars: see https://peter.bourgon.org/go-for-industrial-programming/#testing, https://splice.com/blog/lesser-known-features-go-test/
c) short mode: https://golang.org/pkg/testing/#Short

some preliminary pros/cons after not much research:

• b and c require more setup than a, which is mostly implicit.
• a only on file level, whereas b is per function
• b and c can provide feedback back to user, when -v is used. a has no feedback mechanism afaik.
• according to peter bourgon's best practices long tests should be opt-in, which would rule out c. However, if the go developers made the short flag as to opt-out, then I rather go with how go is actually designed.

I think i would prefer c.