Question

I want to use RSpec mocks to provide canned input to a block.

Ruby:

class Parser   attr_accessor :extracted    def parse(fname)     File.open(fname).each do |line|       extracted = line if line =~ /^RCS file: (.*),v$/     end   end end 

RSpec:

describe Parser   before do     @parser = Parser.new     @lines = mock('lines')     @lines.stub!(:each)     File.stub!(:open).and_return(@lines)   end    it 'should extract a filename into extracted' do     linetext = [ 'RCS file: hello,v\n', 'bla bla bla\n' ]      # HELP ME HERE ...     # the :each should be fed with 'linetext'     @lines.should_receive(:each)      @parser.should_receive('extracted=')     @parser.parse('somefile.txt')   end end 

It’s a way to test that the internals of the block work correctly by passing fixtured data into it. But I can’t figure out how to do the actual feeding with RSpec mocking mechanism.

update: looks like the problem was not with the linetext, but with the:

@parser.should_receive('extracted=') 

it’s not the way it’s called, replacing it in the ruby code with self.extracted= helps a bit, but feels wrong somehow.

Answer 1

I don’t have a computer with Ruby & RSpec available to check this, but I suspect you need to add a call to and_yields call [1] on the end of the should_receive(:each). However, you might find it simpler not to use mocks in this case e.g. you could return a StringIO instance containing linetext from the File.open stub.

[1] http://rspec.rubyforge.org/rspec/1.1.11/classes/Spec/Mocks/BaseExpectation.src/M000104.html