Extract ErrorWithFilteredBacktrace to reduce duplication

lib/mocha/error_with_filtered_backtrace.rb

@@ -0,0 +1,17 @@
+require 'mocha/backtrace_filter'
+
+module Mocha
+
+  # @private
+  class ErrorWithFilteredBacktrace < StandardError
+
+    # @private
+    def initialize(message = nil, backtrace = [])
+      super(message)
+      filter = BacktraceFilter.new
+      set_backtrace(filter.filtered(backtrace))
+    end
+
+  end
+
+end

lib/mocha/not_initialized_error.rb

@@ -1,18 +1,9 @@
-require 'mocha/backtrace_filter'
+require 'mocha/error_with_filtered_backtrace'
 
 module Mocha
 
   # Exception raised when Mocha has not been initialized, e.g. outside the
   # context of a test.
-  class NotInitializedError < StandardError
-
-    # @private
-    def initialize(message = nil, backtrace = [])
-      super(message)
-      filter = BacktraceFilter.new
-      set_backtrace(filter.filtered(backtrace))
-    end
-
-  end
+  class NotInitializedError < ErrorWithFilteredBacktrace; end
 
 end

lib/mocha/stubbing_error.rb

@@ -1,19 +1,10 @@
-require 'mocha/backtrace_filter'
+require 'mocha/error_with_filtered_backtrace'
 
 module Mocha
 
   # Exception raised when stubbing a particular method is not allowed.
   #
   # @see Configuration.prevent
-  class StubbingError < StandardError
-
-    # @private
-    def initialize(message = nil, backtrace = [])
-      super(message)
-      filter = BacktraceFilter.new
-      set_backtrace(filter.filtered(backtrace))
-    end
-
-  end
+  class StubbingError < ErrorWithFilteredBacktrace; end
 
 end