= Flex Mock -- Making Mock Easy FlexMock is a simple mock object for unit testing. The interface is simple, but still provides a good bit of flexibility. Version :: 0.3.0 = Links Documents :: http://onestepback.org/software/flexmock Download :: Use RubyGems to download the flexmock gem from http://gems.rubyforge.org == Installation You can install FlexMock with the following command. $ gem install flexmock == Simple Example We have a data acquisition class (+TemperatureSampler+) that reads a temperature sensor and returns an average of 3 readings. We don't have a _real_ temperature to use for testing, so we mock one up with a mock object that responds to the +read_temperature+ message. Here's the complete example: class TemperatureSampler def initialize(sensor) @sensor = sensor end def average_temp total = (0...3).collect { @sensor.read_temperature }.inject { |i, s| i + s } total / 3.0 end end class TestTemperatureSampler < Test::Unit::TestCase include FlexMock::TestCase def test_tempurature_sampler readings = [10, 12, 14] sensor = flexmock("temp") sensor.should_receive(:read_temperature).and_return { readings.shift } sampler = TemperatureSampler.new(sensor) assert_equal 12, sampler.average_temp # NOTE: # all mocks created by the +flexmock+ method will be # automatically verified during the test teardown. end end == Quick Reference === Expectation Declarators Expectation declarators are used to specify the expectations placed upon received method calls. The following declarators may be used to create the proper expectations on a FlexMock object. * should_receive(symbol) -- Declares that a message named symbol will be sent to the mock object. Further refinements on this expected message (called an expectation) may be chained to the +should_receive+ call. * should_expect -- Creates a mock recording object that will translate received method calls into mock expectations. The recorder is passed to a block supplied with the +should_expect+ method. See examples below. * with(arglist) -- Declares that this expectation matches messages that match the given argument list. The === operator is used on a argument by argument basis to determine matching. This means that most literal values match literally, class values match any instance of a class and regular expression match any matching string (after a +to_s+ conversion). See argument validators (below) for details on argument validation options. * with_any_args -- Declares that this expectation matches the message with any argument (default) * with_no_args -- Declares that this expectation matches messages with no arguments * returns(value) -- Declares that the message will return the given value (returns(nil) is the default). * returns { |args| code ... } -- Declares that the message will return whatever the block calculates. The actual arguments in the message will be passed to the block. * zero_or_more_times -- Declares that the message is may be sent zero or more times (default, equivalent to at_least.never). * once -- Declares that the message is only sent once. at_least / at_most modifiers are allowed. * twice -- Declares that the message is only sent twice. at_least / at_most modifiers are allowed. * never -- Declares that the message is never sent. at_least / at_most modifiers are allowed. * times(n) -- Declares that the message is sent n times. at_least / at_most modifiers are allowed. * at_least -- Modifies the immediately following message count declarator so that it means the message is sent at least that number of times. E.g. at_least.once means the message is sent at least once during the test, but may be sent more often. Both at_least and at_most may be specified on the same expectation. * at_most -- Similar to at_least, but puts an upper limit on the number of messages. Both at_least and at_most may be specified on the same expectation. * ordered -- Declares that the message is ordered and is expected to be received in a certain position in a sequence of messages. The message should arrive after and previously declared ordered messages and prior to any following declared ordered messages. Unordered messages are ignored when considering the message order. * ordered(group) -- Declare that the given method belongs to an order group. Methods within the group may be received in any order. Ordered messages outside the group must be received either before or after the grouped messages. For example, in the following, messages +flip+ and +flop+ may be received in any order (because they are in the same group), but must occur strictly after +start+ but before +end+. The message +any_time+ may be received at any time because it is not ordered. m = FlexMock.new m.should_receive(:any_time) m.should_receive(:start).ordered m.should_receive(:flip).ordered(:flip_flop_group) m.should_receive(:flop).ordered(:flip_flop_group) m.should_receive(:end).ordered === Argument Validation The values passed to the +with+ declarator determine the criteria for matching expectations. The first expectation found that matches the arguments in a mock method call will be used to validate that mock method call. The following rules are used for argument matching: * A +with+ parameter that is a class object will match any actual argument that is an instance of that class. Examples: with(Integer) will match f(3) * A regular expression will match any actual argument that matches the regular expression. Non-string actual arguments are converted to strings via +to_s+ before applying the regular expression. Examples: with(/^src/) will match f("src_object") with(/^3\./) will match f(3.1415972) * Most other objects will match based on equal values. Examples: with(3) will match f(3) with("hello") will match f("hello") * If you wish to override the default matching behavior and force matching by equality, you can use teh FlexMock.eq convenience method. This is mostly used when you wish to match class objects, since the default matching behavior for class objects is to match instances, not themselves. Examples: with(eq(Integer)) will match f(Integer) with(eq(Integer)) will NOT match f(3) Note: If you do not use the FlexMock::TestCase Test Unit integration module, or the FlexMock::ArgumentTypes module, you will have to fully qualify the +eq+ method: with(FlexMock.eq(Integer)) will match f(Integer) with(FlexMock.eq(Integer)) will NOT match f(3) * If you wish to match _anything_, then use the FlexMock.any method in the with argument list. Examples (assumes either the FlexMock::TestCase or FlexMock::ArgumentTypes mix-ins has been included): with(any) will match f(3) with(any) will match f("hello") with(any) will match f(Integer) with(any) will match f(nil) * If you wish to specify a complex matching criteria, use the FlexMock.on(&block) with the logic contained in the block. Examples (assumes FlexMock::ArguementTypes has been included): with(on { |arg| (arg % 2) == 0 } ) will match any even integer. == Examples === Expect multiple queries and a single update The queries my have any arguments. The update must have a specific argument of 5. class TestDb include FlexMock::TestCase def test_db db = flexmock('db') db.should_receive(:query).and_return([1,2,3]) db.should_receive(:update).with(5).and_return(nil).once # test code here end end === Expect all queries before any updates (This and following examples assume that the FlexMock::TestCase module is being used.) All the query message must occur before any of the update messages. def test_query_and_update db = flexmock('db') db.should_receive(:query).and_return([1,2,3]).ordered db.should_recieve(:update).and_return(nil).ordered # test code here end === Expect several queries with different parameters The queries should happen after startup but before finish. The queries themselves may happen in any order (because they are in the same order group). The first two queries should happen exactly once, but the third query (which matches any query call with a four character parameter) may be called multiple times (but at least once). Startup and finish must also happen exactly once. Also note that we use the +with+ method to match different arguement values to figure out what value to return. def test_ordered_queries db = flexmock('db') db.should_receive(:startup).once.ordered db.should_receive(:query).with("CPWR").and_return(12.3). once.ordered(:queries) db.should_receive(:query).with("MSFT").and_return(10.0). once.ordered(:queries) db.should_receive(:query).with(/^....$/).and_return(3.3). at_least.once.ordered(:queries) db.should_receive(:finish).once.ordered # test code here end === Same as above, but using the Record Mode interface The record mode interface offers much the same features as the +should_receive+ interface introduced so far, but it allows the messages to be sent directly to a recording object rather than be specified indirectly using a symbol. def test_ordered_queries_in_record_mode db = flexmock('db') db.should_expect do |rec| rec.startup.once.ordered rec.query("CPWR") { 12.3 }.once.ordered(:queries) rec.query("MSFT") { 10.0 }.once.ordered(:queries) rec.query("^....$/) { 3.3 }.at_least.once.ordered(:queries) rec.finish)once.ordered end # test code here using +db+. end === Using Record Mode to record a known, good algorithm for testing Record mode is nice when you have a known, good algorithm that can use a recording mock object to record the steps. Then you compare the execution of a new algorithm to behavior of the old using the recorded expectations in the mock. For this you probably want to put the recorder in _strict_ mode so that the recorded expectations use exact matching on argument lists, and strict ordering of the method calls. Note: This is most useful when there are no queries on the mock objects, because the query responses cannot be programmed into the recorder object. def test_build_xml builder = flexmock('builder') builder.should_expect do |rec| rec.should_be_strict known_good_way_to_build_xml(rec) # record the messages end new_way_to_build_xml(builder) # compare to new way end === Expect multiple calls, returning a different value each time Sometimes you need to return different values for each call to a mocked method. This example shifts values out of a list for this effect. def test_multiple_gets file = flexmock('file') return_values = ["line 1\n", "line 2\n"] file.should_receive(:gets).with_no_args.and_return { return_values.shift } # test code here end === Ignore uninteresting messages Generally you need to mock only those methods that return an interesting value or wish to assert were sent in a particular manner. Use the +should_ignore_missing+ method to turn on missing method ignoring. def test_an_important_message m = flexmock('m') m.should_recieve(:an_important_message).and_return(1).once m.should_ignore_missing # test code here end Note: The original +mock_ignore_missing+ is now an alias for +should_ignore_missing+. == Classic +mock_handle+ Interface FlexMock still supports the simple +mock_handle+ interface used in the original version of FlexMock. +mock_handle+ is equivalent to the following: def mock_handle(sym, expected_count=nil, &block) self.should_receive(sym).times(expected_count).returns(&block) end == Other Mock Objects ruby-mock :: http://www.b13media.com/dev/ruby/mock.html test-unit-mock :: http://www.deveiate.org/code/Test-Unit-Mock.shtml == License Copyright 2003, 2004, 2005, 2006 by Jim Weirich (jim@weirichhouse.org). All rights reserved. Permission is granted for use, copying, modification, distribution, and distribution of modified versions of this work as long as the above copyright notice is included. = Other stuff Author:: Jim Weirich Requires:: Ruby 1.8.x or later == Warranty This software is provided "as is" and without any express or implied warranties, including, without limitation, the implied warranties of merchantibility and fitness for a particular purpose.