How to use custom RR wildcard matcher?

Question

I have created a wildcard matcher for RR that matches JSON strings by parsing them into hashes. This is because JSON (de)serialization doesn't preserve order; if we have:

{ 'foo': 42, 'bar': 123 }

... then after (de)serialization, we might find that our update method is called with:

{ 'bar': 123, 'foo': 42 }

The wildcard matcher looks like this:

class RR::WildcardMatchers::MatchesJsonString

  attr_reader :expected_json_hash

  def initialize(expected_json_string)
    @expected_json_hash = JSON.parse(expected_json_string)
  end

  def ==(other)
    other.respond_to?(:expected_json_hash) && other.expected_json_hash == self.expected_json_hash
  end

  def wildcard_matches?(actual_json_string)
    actual_json_hash = JSON.parse(actual_json_string)
    @expected_json_hash == actual_json_hash
  end
end

module RR::Adapters::RRMethods
  def matches_json(expected_json_string)
    RR::WildcardMatchers::MatchesJsonString.new(expected_json_string)
  end
end

... and we're using it like:

describe 'saving manifests' do

  before do
    @manifests = [
      { :sections => [], 'title' => 'manifest1' },
      { :sections => [], 'title' => 'manifest2' }
    ]

    mock(manifest).create_or_update!(matches_json(@manifests[0].to_json)) { raise 'uh oh' }
    mock(manifest).create_or_update!(matches_json(@manifests[1].to_json))

    parser = ContentPack::ContentPackParser.new({
                                                  'manifests' => @manifests
                                                })
    @errors = parser.save
  end

  it 'updates manifests' do
    manifest.should have_received.create_or_update!(anything).twice
  end
end

This in accordance with the RR documentation. However, instead of mock() expecting an argument that matches JSON, it expects the argument to be a MatchesJsonString object:

 1) ContentPack::ContentPackParser saving manifests updates manifests
     Failure/Error: mock(Manifest).create_or_update!(matches_json(@manifests[0].to_json)) { raise 'uh oh' }
     RR::Errors::TimesCalledError:
       create_or_update!(#<RR::WildcardMatchers::MatchesJsonString:0x13540def0 @expected_json_hash={"title"=>"manifest1", "sections"=>[]}>)
       Called 0 times.
       Expected 1 times.
     # ./spec/models/content_pack/content_pack_parser_spec.rb:196

While posting I noticed that there have been a grand total of 15 questions tagged with 'rr'. I suspect the first answer might be along the lines of "don't use rr" ;-) — Duncan Bayne, Nov 05 '12 at 00:34

score 0 · Accepted Answer · answered Nov 05 '12 at 00:47

The answer is that there's a typo in the documentation to which I linked. This (my emphasis):

#wildcard_matches?(other)

wildcard_matches? is the method that actually checks the argument against the expectation. It should return true if other is considered to match, false otherwise. In the case of DivisibleBy, wildcard_matches? reads:

... should actually read:

#wildcard_match?(other)

...

One of my colleagues suggested that we compare our code with one of the matchers defined in the rr gem, and then the difference stood out.

How to use custom RR wildcard matcher?

1 Answers1