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Add information on mocking an external function #51

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Add information on mocking an external function #51

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9350f5e
Add information on mocking an external function
rnelson0 Apr 24, 2023
311c55c
Denote possible spec helper file paths for PDK and non-PDK users
rnelson0 Apr 25, 2023
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25 changes: 25 additions & 0 deletions docs/documentation/functions/index.md
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Expand Up @@ -97,3 +97,28 @@ describe 'ensure_resource' do
end
end
{% endhighlight %}

## Mocking a function for use in all tests

You may not need to test a function itself, but a calling class may require the function
to return a value. You can mock the function once and make it available to all test.
Modify *spec/spec_helper_local.rb* and use `Puppet::Parser::Functions.newfunction()`
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rspec-puppet really doesn't mention spec_helper_local.rb anywhere. That's really a PDK-thing and I'd avoid it here.

to add the function inside of an `RSpec.configure` block. For example:

{% highlight ruby %}
RSpec.configure do | c|
c.before :each do
# The vault_lookup function takes a single argument and returns a hash with three keys
Puppet::Parser::Functions.newfunction(:vault_lookup, type: :rvalue) do |_args|
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This is the legacy function API. The current standard should be used everywhere.

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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.

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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.

{
domain: 'test',
username: 'test',
password: 'test'
}
end
end
end
{% endhighlight %}

You may add multiple functions and other configuration elements inside the `c.before :each do`
block and all will be available inside every test.