How to get the content of a rendered .erb template as a string?

[enricovianello]

I have a resource which creates an XML file via an erb template and I'd like to test its content via XPath. I found Nokogiri library and it works but I need to access the content of the rendered file as a string.

I tried:

content = catalogue.resource('file', '/path/to/file.xml').send(:parameters)[:content]

but I get:

undefined method `parameters' for nil:NilClass

My puppet version is 5.5.17.
Is there an alternative way to access the content of a rendered .erb template as a string?

[ekohl]

Why can't you use contain_file('/path/to/file.xml').with_content()?

[enricovianello]

@ekohl Because I'd like to query the content of my XML file with XPath, in order to improve the maintainability of my tests but, for all I know, only a regex is supported with .with_content () method. Or am I wrong?

[ekohl]

This happens when the resource is not found in the catalog. We have similar helpers and they start with is_expected.to contain_file(title) to ensure the resource is actually in the catalog. Currently in our modules we have a helper:

def get_content(subject, title)
  is_expected.to contain_file(title)
  content = subject.resource('file', title).send(:parameters)[:content]
  content.split(/\n/).reject { |line| line =~ /(^#|^$|^\s+#)/ }
end

While looking at this issue, I checked the source and the alternative is to use a proc:

it { is_expected.to contain_concat__fragment(title).with_content(Proc.new { |content| content.split("\n") & expected_lines == expected_lines}) }

The downside of this is that the error reporting is not great: the to_s of a Proc is not useful. This leads to failures (cut down for readability):

expected that the catalogue would contain Concat::Fragment[foreman_settings+01-header.yaml] with content set to #<Proc:0x0000564ec832c950@/home/ekohl/dev/puppet-foreman/spec/spec_helper.rb:61> but it is set to "---\n### File managed with puppet ###\n## Module:
Diff:
@@ -1,2 +1,62 @@
-#<Proc:0x0000564ec832c950@/home/ekohl/dev/puppet-foreman/spec/spec_helper.rb:61>
+---
+### File managed with puppet ###
+## Module:           'foreman'

A more advanced example would be to use a class:

class ValidateConcatFragmentContent
  def initialize(expected_lines)
    @expected_lines = expected_lines
  end

  def call(content)
    content.split("\n") & @expected_lines == @expected_lines
  end

  def to_s
    @expected_lines.join("\n")
  end
end

it { is_expected.to contain_concat__fragment(title).with_content(ValidateConcatFragmentContent.new(expected_lines)) }

Now the error reporting is better:

expected that the catalogue would contain Concat::Fragment[foreman_settings+01-header.yaml] with content set to #<ValidateConcatFragmentContent:0x0000557a165390b8 @expected_lines=[":lgging:", "  :level: info", "  :production:", "    :type: journald", "    :layout: pattern"]> but it is set to "---\n### File managed with puppet ###\n## Module:           'foreman'
Diff:

@@ -1,6 +1,62 @@
-:lgging:
+---
+### File managed with puppet ###
+## Module:           'foreman'
+:logging:
   :level: info
   :production:
     :type: journald
     :layout: pattern

Perhaps the code should be extended to allow raising an error to allow customizing the message. See

rspec-puppet/lib/rspec-puppet/matchers/parameter_matcher.rb

Lines 73 to 78 in 6db5fb0

	def check_proc(expected, actual)
	expected_return = @should_match
	actual_return = expected.call(actual)
	actual_return == expected_return
	end

[ekohl]

Looking closer it appears the call was not actually called since it's now a class and not a proc. It just matched the to_s representation. It may be better to write a custom matcher or use the workaround of first checking if the catalog really contains the desired resource.