def explain_expectations
result = ''
result += "from #{@sender} " if instance_variable_defined?('@sender')
result += "to #{@recipients.inspect} " if instance_variable_defined?('@recipients')
result += "with subject \"#{@subject}\" " if instance_variable_defined?('@subject')
result += "with subject matching \"#{@subject_matcher}\" " if instance_variable_defined?('@subject_matcher')
result += "with body \"#{@body}\" " if instance_variable_defined?('@body')
result += "with body matching \"#{@body_matcher}\" " if instance_variable_defined?('@body_matcher')
result
end