diff --git a/lib/thor/actions/inject_into_file.rb b/lib/thor/actions/inject_into_file.rb
index be13ddb2..51aed970 100644
--- a/lib/thor/actions/inject_into_file.rb
+++ b/lib/thor/actions/inject_into_file.rb
@@ -2,6 +2,38 @@
 
 class Thor
   module Actions
+    WARNINGS = {unchanged_no_flag: "File unchanged! Either the supplied flag value not found or the content has already been inserted!"}
+
+    # Injects the given content into a file, raising an error if the contents of
+    # the file are not changed. Different from gsub_file, this method is reversible.
+    #
+    # ==== Parameters
+    # destination<String>:: Relative path to the destination root
+    # data<String>:: Data to add to the file. Can be given as a block.
+    # config<Hash>:: give :verbose => false to not log the status and the flag
+    #                for injection (:after or :before) or :force => true for
+    #                insert two or more times the same content.
+    #
+    # ==== Examples
+    #
+    #   insert_into_file "config/environment.rb", "config.gem :thor", :after => "Rails::Initializer.run do |config|\n"
+    #
+    #   insert_into_file "config/environment.rb", :after => "Rails::Initializer.run do |config|\n" do
+    #     gems = ask "Which gems would you like to add?"
+    #     gems.split(" ").map{ |gem| "  config.gem :#{gem}" }.join("\n")
+    #   end
+    #
+    def insert_into_file!(destination, *args, &block)
+      data = block_given? ? block : args.shift
+
+      config = args.shift || {}
+      config[:after] = /\z/ unless config.key?(:before) || config.key?(:after)
+      config = config.merge({error_on_no_change: true})
+
+      action InjectIntoFile.new(self, destination, data, config)
+    end
+    alias_method :inject_into_file!, :insert_into_file!
+
     # Injects the given content into a file. Different from gsub_file, this
     # method is reversible.
     #
@@ -21,8 +53,6 @@ module Actions
     #     gems.split(" ").map{ |gem| "  config.gem :#{gem}" }.join("\n")
     #   end
     #
-    WARNINGS = {unchanged_no_flag: "File unchanged! Either the supplied flag value not found or the content has already been inserted!"}
-
     def insert_into_file(destination, *args, &block)
       data = block_given? ? block : args.shift
 
@@ -47,6 +77,7 @@ def initialize(base, destination, data, config)
 
         @replacement = data.is_a?(Proc) ? data.call : data
         @flag = Regexp.escape(@flag) unless @flag.is_a?(Regexp)
+        @error_on_no_change = @config.fetch(:error_on_no_change, false)
       end
 
       def invoke!
@@ -59,6 +90,8 @@ def invoke!
         if exists?
           if replace!(/#{flag}/, content, config[:force])
             say_status(:invoke)
+          elsif @error_on_no_change
+            raise Thor::Error, "The content of #{destination} did not change"
           elsif replacement_present?
             say_status(:unchanged, color: :blue)
           else
diff --git a/spec/actions/inject_into_file_spec.rb b/spec/actions/inject_into_file_spec.rb
index 6ba6dcd6..e46a60c9 100644
--- a/spec/actions/inject_into_file_spec.rb
+++ b/spec/actions/inject_into_file_spec.rb
@@ -20,6 +20,10 @@ def invoke!(*args, &block)
     capture(:stdout) { invoker.insert_into_file(*args, &block) }
   end
 
+  def invoke_with_a_bang!(*args, &block)
+    capture(:stdout) { invoker.insert_into_file!(*args, &block) }
+  end
+
   def revoke!(*args, &block)
     capture(:stdout) { revoker.insert_into_file(*args, &block) }
   end
@@ -170,6 +174,164 @@ def file
         end
       end
     end
+
+    context "with a bang" do
+      it "changes the file adding content after the flag" do
+        invoke_with_a_bang! "doc/README", "\nmore content", after: "__start__"
+        expect(File.read(file)).to eq("__start__\nmore content\nREADME\n__end__\n")
+      end
+
+      it "changes the file adding content before the flag" do
+        invoke_with_a_bang! "doc/README", "more content\n", before: "__end__"
+        expect(File.read(file)).to eq("__start__\nREADME\nmore content\n__end__\n")
+      end
+
+      it "appends content to the file if before and after arguments not provided" do
+        invoke_with_a_bang!("doc/README", "more content\n")
+        expect(File.read(file)).to eq("__start__\nREADME\n__end__\nmore content\n")
+      end
+
+      it "does not change the file and raises an error if replacement present in the file" do
+        invoke_with_a_bang!("doc/README", "more specific content\n")
+        expect do
+          invoke_with_a_bang!("doc/README", "more specific content\n")
+        end.to raise_error(Thor::Error, "The content of #{destination_root}/doc/README did not change")
+      end
+
+      it "does not change the file and raises an error if flag not found in the file" do
+        expect do
+          invoke_with_a_bang!("doc/README", "more content\n", after: "whatever")
+        end.to raise_error(Thor::Error, "The content of #{destination_root}/doc/README did not change")
+      end
+
+      it "accepts data as a block" do
+        invoke_with_a_bang! "doc/README", before: "__end__" do
+          "more content\n"
+        end
+
+        expect(File.read(file)).to eq("__start__\nREADME\nmore content\n__end__\n")
+      end
+
+      it "logs status" do
+        expect(invoke_with_a_bang!("doc/README", "\nmore content", after: "__start__")).to eq("      insert  doc/README\n")
+      end
+
+      it "logs status if pretending" do
+        invoker(pretend: true)
+        expect(invoke_with_a_bang!("doc/README", "\nmore content", after: "__start__")).to eq("      insert  doc/README\n")
+      end
+
+      it "does not change the file if pretending" do
+        invoker pretend: true
+        invoke_with_a_bang! "doc/README", "\nmore content", after: "__start__"
+        expect(File.read(file)).to eq("__start__\nREADME\n__end__\n")
+      end
+
+      it "does not change the file and raises an error if already includes content" do
+        invoke_with_a_bang! "doc/README", before: "__end__" do
+          "more content\n"
+        end
+
+        expect(File.read(file)).to eq("__start__\nREADME\nmore content\n__end__\n")
+
+        expect do
+          invoke_with_a_bang! "doc/README", before: "__end__" do
+            "more content\n"
+          end
+        end.to raise_error(Thor::Error, "The content of #{destination_root}/doc/README did not change")
+
+        expect(File.read(file)).to eq("__start__\nREADME\nmore content\n__end__\n")
+      end
+
+      it "does not change the file and raises an error if already includes content using before with capture" do
+        invoke_with_a_bang! "doc/README", before: /(__end__)/ do
+          "more content\n"
+        end
+
+        expect(File.read(file)).to eq("__start__\nREADME\nmore content\n__end__\n")
+
+        expect do
+          invoke_with_a_bang! "doc/README", before: /(__end__)/ do
+            "more content\n"
+          end
+        end.to raise_error(Thor::Error, "The content of #{destination_root}/doc/README did not change")
+
+        expect(File.read(file)).to eq("__start__\nREADME\nmore content\n__end__\n")
+      end
+
+      it "does not change the file and raises an error if already includes content using after with capture" do
+        invoke_with_a_bang! "doc/README", after: /(README\n)/ do
+          "more content\n"
+        end
+
+        expect(File.read(file)).to eq("__start__\nREADME\nmore content\n__end__\n")
+
+        expect do
+          invoke_with_a_bang! "doc/README", after: /(README\n)/ do
+            "more content\n"
+          end
+        end.to raise_error(Thor::Error, "The content of #{destination_root}/doc/README did not change")
+
+        expect(File.read(file)).to eq("__start__\nREADME\nmore content\n__end__\n")
+      end
+
+      it "does not attempt to change the file if it doesn't exist - instead raises Thor::Error" do
+        expect do
+          invoke_with_a_bang! "idontexist", before: "something" do
+            "any content"
+          end
+        end.to raise_error(Thor::Error, /does not appear to exist/)
+        expect(File.exist?("idontexist")).to be_falsey
+      end
+
+      it "does not attempt to change the file if it doesn't exist and pretending" do
+        expect do
+          invoker pretend: true
+          invoke_with_a_bang! "idontexist", before: "something" do
+            "any content"
+          end
+        end.not_to raise_error
+        expect(File.exist?("idontexist")).to be_falsey
+      end
+
+      it "does change the file if already includes content and :force is true" do
+        invoke_with_a_bang! "doc/README", before: "__end__" do
+          "more content\n"
+        end
+
+        expect(File.read(file)).to eq("__start__\nREADME\nmore content\n__end__\n")
+
+        invoke_with_a_bang! "doc/README", before: "__end__", force: true do
+          "more content\n"
+        end
+
+        expect(File.read(file)).to eq("__start__\nREADME\nmore content\nmore content\n__end__\n")
+      end
+
+      it "can insert chinese" do
+        encoding_original = Encoding.default_external
+
+        begin
+          silence_warnings do
+            Encoding.default_external = Encoding.find("UTF-8")
+          end
+          invoke_with_a_bang! "doc/README.zh", "\n中文", after: "__start__"
+          expect(File.read(File.join(destination_root, "doc/README.zh"))).to eq("__start__\n中文\n说明\n__end__\n")
+        ensure
+          silence_warnings do
+            Encoding.default_external = encoding_original
+          end
+        end
+      end
+
+      it "does not mutate the provided config" do
+        config = {after: "__start__"}
+        invoke_with_a_bang! "doc/README", "\nmore content", config
+        expect(File.read(file)).to eq("__start__\nmore content\nREADME\n__end__\n")
+
+        expect(config).to eq({after: "__start__"})
+      end
+    end
   end
 
   describe "#revoke!" do