Move the use of VerifyType in consumer packages to unit tests

[dprotaso]

We're using duck.VerifyType to enforce that serialization formats match. These statements are being placed in packages as follows:

pkg/apis/duck/v1alpha1/targetable_types.go

Line 37 in 2b6bdab

var _ = duck.VerifyType(&Target{}, &Targetable{})

This technique means verify is invoked at runtime during package initialization.

As we add more potential types that need to be verified this package initialization technique has an affect on a program's startup.

To avoid this startup time cost, we can simply move these assertions to unit tests that invoke VerifyType

func TestTargetImplementsTargetable(t *testing.T) {
  duck.VerifyType(&Target{}, &Targetable{}) 
}

[dprotaso]

Similarly the use of

var _ duck.Implementable = (*Targetable)(nil)

is not an issue as it's a compile time check

[dprotaso]

/kind good-first-issue

[dprotaso]

/assign @vdemeester

[knative-prow-robot]

@dprotaso: GitHub didn't allow me to assign the following users: vdemeester.

Note that only knative members and repo collaborators can be assigned.
For more information please see the contributor guide

In response to this:

/assign @vdemeester

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[dprotaso]

Uses in other repos

Serving: https://github.com/knative/serving/search?q=%22VerifyType%22&unscoped_q=%22VerifyType%22
Eventing: https://github.com/knative/eventing/search?q=%22VerifyType%22&unscoped_q=%22VerifyType%22
Build: https://github.com/knative/build/search?q=%22VerifyType%22&unscoped_q=%22VerifyType%22

[mattmoor]

This is done.