Adding support for custom JS DB strategies

lib/cucumber/rails/database.rb

@@ -1,11 +1,23 @@
 module Cucumber
   module Rails
     module Database
+
+      CUSTOM_STRATEGY_INTERFACE = %w{ before_js before_non_js }
+
       class << self
 
         def javascript_strategy=(strategy)
-          strategy_type = map[strategy] || raise("The strategy '#{strategy}' is not understood. Please use one of #{map.keys.join(',')}")
+          strategy_type =
+            case strategy
+            when Symbol
+              map[strategy] || raise("The strategy '#{strategy}' is not understood. Please use one of #{map.keys.join(',')}")
+            when Class
+              strategy
+            end
+
           @strategy = strategy_type.new
+
+          validate_interface!
         end
 
         def before_js
@@ -26,6 +38,12 @@ def map
           }
         end
 
+        def validate_interface!
+          unless CUSTOM_STRATEGY_INTERFACE.all? {|m| @strategy.respond_to?(m) }
+            raise(ArgumentError, "Strategy must respond to all of: #{CUSTOM_STRATEGY_INTERFACE.map{|method| "##{method}" } * '  '} !")
+          end
+        end
+
       end
 
       class SharedConnectionStrategy

spec/cucumber/rails/database_spec.rb

@@ -0,0 +1,62 @@
+# -*- encoding: utf-8 -*-
+
+require 'spec_helper'
+require 'cucumber'
+
+require 'rails'
+require 'active_record'
+require 'cucumber/rails/database'
+
+
+describe Cucumber::Rails::Database do
+
+  class QuickCallback
+    @@callbacks = Hash.new {|h,k| h[k] = []}
+    def self.add_callback(name, block)
+      @@callbacks[name] << block
+    end
+
+    def self.run!(name)
+      @@callbacks[name].map(&:call)
+    end
+  end
+
+  class Object
+    def Before(name, &block)
+      QuickCallback.add_callback(name, block)
+    end
+  end
+
+  it 'should accept custom JS DB strategies' do
+    require 'lib/cucumber/rails/hooks/active_record'
+
+    class ValidStrategy
+      def before_js
+        # Anything
+      end
+
+      def before_non_js
+        # Likewise
+      end
+    end
+
+    Cucumber::Rails::Database.javascript_strategy = ValidStrategy
+    # Fun Ruby fact (@frf): foo=(a) will ALWAYS return a (unless you do send(:foo=, a))
+    strategy = Cucumber::Rails::Database.instance_variable_get(:@strategy)
+    strategy.should_receive(:before_js).once
+    QuickCallback.run!('@javascript')
+
+    strategy.should_receive(:before_non_js).once
+    QuickCallback.run!('~@javascript')
+  end
+
+  it 'should reject invalid JS DB strategies' do
+    require 'lib/cucumber/rails/hooks/active_record'
+
+    class InvalidStrategy
+    end
+
+    lambda { Cucumber::Rails::Database.javascript_strategy = InvalidStrategy }.should raise_error(ArgumentError)
+  end
+
+end