Add information on mocking an external function

[rnelson0]

When not testing the function itself, you still need to mock it so it's available to the calling class.

[CLAassistant]

All committers have signed the CLA.

[ekohl]

rspec-puppet really doesn't mention spec_helper_local.rb anywhere. That's really a PDK-thing and I'd avoid it here.

[ekohl]

This is the legacy function API. The current standard should be used everywhere.

[rnelson0]

There's some discussion of that in slack and how it would apply to tests, there's not a lot of clarity there and the "obvious" code doesn't seem to work. Very happy to move to that if we can determine the correct syntax to use.

[ekohl]

I'm looking at the function testing code and Puppet.override looks promising. It is a private API of Puppet, but looks promising.

rspec-puppet/lib/rspec-puppet/example/function_example_group.rb

Lines 87 to 108 in f4c5c71

	def find_function(function_name = self.class.top_level_description)
	with_vardir do
	env = adapter.current_environment
	if Puppet.version.to_f >= 4.0
	context_overrides = compiler.context_overrides
	func = nil
	loaders = Puppet.lookup(:loaders)
	Puppet.override(context_overrides, 'rspec-test scope') do
	func = V4FunctionWrapper.new(function_name,
	loaders.private_environment_loader.load(:function, function_name), context_overrides)
	@scope = context_overrides[:global_scope]
	end
	return func if func.func
	end
	if Puppet::Parser::Functions.function(function_name)
	V3FunctionWrapper.new(function_name, scope.method("function_#{function_name}".intern))
	end
	end
	end

Another problem you may have with the modern API is that it prefers namespaced functions, or there's a difference in priority.

[gavindidrichsen]

Thanks for your contributions here @rnelson0 , @ekohl.

As it seems there's still a bit of discussion about the implementation details, I'm going to move this draft. We'll certainly have a look again at this whenever it comes back up.