Rspec given

:construction: 
With given, anything can be the content of a  `Then` clause, and if it's "true" the clause succeeds, otherwise it fails. This means that you can have
```ruby
Then { header_to_xml_to_s.include? "<FromEANNumber>1111111111111</FromEANNumber>" }
```
and it will be semantically equivalent and easier on the eyes. Also the failure parser will have an easier job to show what exactly fails (the typical drawback of `assert_true` and `.should be_true` is that the error message is like "false should have been true"... thank you very much for the information :grinning: )