v4: Only permit integration through API methods exposed through nunit.engine.api

[ChrisMaddock]

We've faced various issues in v3 with it being unclear which public exposed methods are intended to be supported as interfaces. This leads to unexpected breaking changes for runners maintainers, and also lost time in trying to support interactivity with the engine through a range of unsupported methods.

For v4, I suggest we make only the methods in nunit.engine.api.dll publicly accessible. To do this, we would make methods internal in the other assemblies, and use InternalsVisibleTo to allow interaction between different assemblies.

[CharliePoole]

Minor thing: I'd add "or any other API assemblies we decide we need."

[CharliePoole]

We've made the basic decision: only API methods are guaranteed to remain stable. It remains to make current public methods internal or otherwise inaccessible to the greatest extent possible.

[CharliePoole]

@nunit/engine-team

Excluding test and testdata assemblies, The following projects need to be reviewed and fixed as necessary. They are listed in top-down order, which is probably the easiest way to deal with them.

I also excluded the agent projects, since they are about to disappear, becoming separately maintained pluggable agent extensions. For that reason, anything needed by the agents from nunit.agent.core should remain public.

• nunit4-console
• nunit4-netcore-console
• nunit.engine
• nunit.agent.core
• nunit.extensibility
• nunit.common

If you have time to do one of these tasks, please edit to put your name or GitHub id on the same line, like this (@CharliePoole) or this (Charlie).