Refactor TestFakerDeprecation

This is a proposed change to the `TestFakerDeprecation` class that makes
it easier for developers to add new tests for deprecations.  The
introduced `DEPRECATION_MAPPINGS` hash allows for devs to add new tests
in one location.

test/test_faker_deprecator.rb

@@ -3,21 +3,32 @@
 require_relative 'test_helper'
 
 class TestFakerDeprecation < Test::Unit::TestCase
+  ##
+  # A hash that maps deprecated methods to their new counterparts.
+  #
+  # @return [Hash{Array<String, String> => Array<String, String>}]
+  #
+  # @example Add the following into the hash
+  #  ['Faker::OldKlass', 'old_method'] => ['Faker::NewKlass', 'new_method']
+  DEPRECATION_MAPPINGS = {
+    ['Faker::IDNumber', 'valid'] => ['Faker::IdNumber', 'valid'],
+    ['Faker::JapaneseMedia::FmaBrotherhood', 'character'] => ['Faker::JapaneseMedia::FullmetalAlchemistBrotherhood', 'character']
+  }.freeze
+
   def test_using_a_deprecated_generator_returns_a_warning_message
     actual_stdout, actual_stderr = capture_output do
-      Faker::IDNumber.valid
-      Faker::JapaneseMedia::FmaBrotherhood.character
+      DEPRECATION_MAPPINGS.each_key { |klass, method| Object.const_get(klass).send(method) }
     end
 
-    assert_includes(actual_stdout, 'DEPRECATION WARNING: Faker::IDNumber is deprecated. Use Faker::IdNumber instead')
-    assert_includes(actual_stdout, 'DEPRECATION WARNING: Faker::JapaneseMedia::FmaBrotherhood is deprecated. Use Faker::JapaneseMedia::FullmetalAlchemistBrotherhood instead')
+    DEPRECATION_MAPPINGS.each do |(deprecated_klass, _deprecated_method), (new_klass, _new_method)|
+      assert_includes(actual_stdout, "DEPRECATION WARNING: #{deprecated_klass} is deprecated. Use #{new_klass} instead")
+    end
     assert_empty(actual_stderr)
   end
 
   def test_using_a_non_deprecated_generator_does_not_return_a_warning_message
     actual_stdout, actual_stderr = capture_output do
-      Faker::IdNumber.valid
-      Faker::JapaneseMedia::FullmetalAlchemistBrotherhood.character
+      DEPRECATION_MAPPINGS.each_value { |klass, method| Object.const_get(klass).send(method) }
     end
 
     assert_empty(actual_stdout)