Add unit tests for Changit::Merger

lib/changit/config_merger.rb

@@ -5,6 +5,7 @@ def initialize(src_config, target_config)
       @target = target_config
     end
 
+    # comapre and merge src_config into target_config into a lexer
     def merge
       src_lexer = Lexer.new(@src)
       src_token_hash = src_lexer.token_hash
@@ -21,12 +22,17 @@ def merge
           end
         end
 
-        config_difference = src_token_hash.dup.delete_if { |k, _| target_token_hash.key?(k) }
+        config_difference = hash_difference(src_token_hash, target_token_hash)
         target_token_hash.merge!(config_difference)
         target_lexer.reconstruct_tokens_from_hash!
       end
 
       target_lexer
     end
+
+    # return the difference between two hashes
+    def hash_difference(src_token_hash, target_token_hash)
+      src_token_hash.dup.delete_if { |k, _| target_token_hash.key?(k) }
+    end
   end
 end

test/merger_test.rb

@@ -0,0 +1,25 @@
+require 'test_helper'
+require 'changit/lexer'
+require 'changit/lexer/section_token'
+
+class ConfigMergerTest < Minitest::Test
+  def test_merge
+    merger = config_merger
+    merged_config = merger.merge
+
+    assert_kind_of Changit::Lexer, merged_config
+  end
+
+  def test_hash_difference
+    difference_hash = config_merger.hash_difference({ "key1" => 1, "key2" => 2 }, { "key1" => 7 })
+    assert_equal difference_hash, { "key2" => 2 }
+  end
+
+  private
+
+  def config_merger
+    src_config = "[user]\n\tname = anothername\n".freeze
+    target_config = "[user]\n\tname = testname\n\temail = testmail@domain.com\n[core]\n\teditor = vim\n[color]\n\tui = true\n[rebase]\n\tautosquash = true\n".freeze
+    Changit::ConfigMerger.new(src_config, target_config)
+  end
+end