CollectionAssert.Contains has misleading parameters and/or output

[stevenaw]

Issue https://github.com/nunit/nunit/issues/4185 was filed against the framework which, after investigation, we determined that the actual parameter on the set-based CollectionAssert methods is actually treated as the expected value, leading to some confusion about the failure message output. Changing the parameter name carries a risk of breaking anyone passing values using named parameters, which isn't worth the risk here so a decision was made to tackle it in documentation instead.

This ticket is to track the documentation update to clarify this.

[MaxAtoms]

Small correction: The second actual should be replaced with expected. Thanks for creating the issue, @stevenaw !

[stevenaw]

Oops, thanks for catching that! I've updated the description