*: add some initial tests for every command

[cgonyeo]

Each command supported by acbuild should have at least one functional test.

• annotation
• begin
• cat-manifest
• copy
• dependency
• end
• environment
• isolator
• label
• mount
• port
• replace-manifest
• run
• set-event-handler
• set-exec
• set-group
• set-name
• set-user
• set-working-directory
• write

[jonboulle]

Perhaps you could edit your comment to add a check-list for this one.

[jonboulle]

One possibility is to do something like fleet: https://github.com/coreos/fleet/blob/master/functional/util/util.go#L29
https://github.com/coreos/fleet/blob/master/functional/README.md

(rkt is similar but rather more complex)