diff --git a/Gemfile b/Gemfile
index f6df068e2a2..192f350a0f6 100644
--- a/Gemfile
+++ b/Gemfile
@@ -188,6 +188,7 @@ group :development do
   gem 'librarian', '>= 0.0.25', require: false
   gem 'annotate'
   gem 'foreman', require: false
+  gem 'metamorpher', '~> 0.1.0'
 end
 
 # Gem that enables support for plugins. It is required.
diff --git a/refactorings/where_dot_first_to_find_by/app.rb b/refactorings/where_dot_first_to_find_by/app.rb
new file mode 100644
index 00000000000..7645623eea6
--- /dev/null
+++ b/refactorings/where_dot_first_to_find_by/app.rb
@@ -0,0 +1,50 @@
+require "optparse"
+require_relative "refactorers/refactor_where_first_to_find_by.rb"
+require_relative "refactorers/refactor_where_first_not_called_expectations.rb"
+require_relative "refactorers/refactor_where_first_mocks.rb"
+require_relative "refactorers/refactor_where_first_strict_mocks.rb"
+
+options = { overwrite: true }
+OptionParser.new do |opts|
+  opts.banner = "Usage: refactorer.rb [options]"
+
+  opts.on("-d", "--dry-run", "Write changes to console, rather than to source files.") do |v|
+    options[:overwrite] = false
+  end
+end.parse!
+
+source_dir = ARGV.first || "."
+base = File.expand_path(File.join("**", "*.rb"), source_dir)
+puts "Refactoring in source directory: #{base}"
+
+[
+  # Refactor "where(...).first -> find_by(...)"
+  RefactorWhereFirstToFindBy,
+
+  # Refactor ".expect(:where).never" to ".expect(:find_by).never"
+  RefactorWhereFirstNotCalledExpectations,
+
+  # Refactor ".expect(:where).return([X])" to ".expect(:find_by).return(X)"
+  #      and ".stubs(:where).return([X])" to ".stubs(:find_by).return(X)"
+  RefactorWhereFirstMocks,
+
+  # Refactor ".expect(:where).with(...).return([X])" to ".expect(:find_by).with(...).return(X)"
+  RefactorWhereFirstStrictMocks
+
+].each do |refactorer|
+  refactorer.new.refactor_files(Dir.glob(base)) do |path, refactored, changes|
+    if changes.empty?
+      puts "No changes in #{path}"
+
+    else
+      puts "In #{path}:"
+
+      changes.each do |change|
+        puts "\tAt #{change.original_position}, inserting:\n\t\t#{change.refactored_code}"
+        puts ""
+      end
+
+      File.open(path, "w") { |f| f.write(refactored) } if options[:overwrite]
+    end
+  end
+end
diff --git a/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_mocks.rb b/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_mocks.rb
new file mode 100644
index 00000000000..628fdaa3a30
--- /dev/null
+++ b/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_mocks.rb
@@ -0,0 +1,31 @@
+require "metamorpher"
+
+class RefactorWhereFirstMocks
+  include Metamorpher::Refactorer
+  include Metamorpher::Builders::Ruby
+
+  def pattern
+    builder
+     .build("TYPE.DOUBLE_METHOD(:where).returns(ARRAY_VALUE)")
+     .ensuring("DOUBLE_METHOD") { |m| m.name == :expects || m.name == :stubs }
+     .ensuring("ARRAY_VALUE") { |v| v.name == :array }
+     # Doesn't match non-array return types, such as Topic.stubs(:where).returns(Topic)
+  end
+
+  def replacement
+    builder
+     .build("TYPE.DOUBLE_METHOD(:find_by).returns(SINGLE_VALUE)")
+     .deriving("SINGLE_VALUE", "ARRAY_VALUE") { |array_value| take_first(array_value) }
+  end
+
+  private
+
+  # Refactor the argument from [] to nil, or from [X] to X
+  def take_first(array_value)
+    if array_value.children.empty?
+      builder.build("nil")
+    else
+      array_value.children.first
+    end
+  end
+end
diff --git a/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_not_called_expectations.rb b/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_not_called_expectations.rb
new file mode 100644
index 00000000000..6edf5f4e8c7
--- /dev/null
+++ b/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_not_called_expectations.rb
@@ -0,0 +1,14 @@
+require "metamorpher"
+
+class RefactorWhereFirstNotCalledExpectations
+  include Metamorpher::Refactorer
+  include Metamorpher::Builders::Ruby
+
+  def pattern
+    builder.build("TYPE.expects(:where).never")
+  end
+
+  def replacement
+    builder.build("TYPE.expects(:find_by).never")
+  end
+end
diff --git a/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_strict_mocks.rb b/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_strict_mocks.rb
new file mode 100644
index 00000000000..51470f2b2e8
--- /dev/null
+++ b/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_strict_mocks.rb
@@ -0,0 +1,27 @@
+require "metamorpher"
+
+class RefactorWhereFirstStrictMocks
+  include Metamorpher::Refactorer
+  include Metamorpher::Builders::Ruby
+
+  def pattern
+    builder.build("TYPE.expects(:where).with(PARAMS_).returns(ARRAY_VALUE)")
+  end
+
+  def replacement
+    builder
+     .build("TYPE.expects(:find_by).with(PARAMS_).returns(SINGLE_VALUE)")
+     .deriving("SINGLE_VALUE", "ARRAY_VALUE") { |array_value| take_first(array_value) }
+  end
+
+  private
+
+  # Refactor the argument from [] to nil, or from [X] to X
+  def take_first(array_value)
+    if array_value.children.empty?
+      builder.build("nil")
+    else
+      array_value.children.first
+    end
+  end
+end
diff --git a/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_to_find_by.rb b/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_to_find_by.rb
new file mode 100644
index 00000000000..4632deeba0a
--- /dev/null
+++ b/refactorings/where_dot_first_to_find_by/refactorers/refactor_where_first_to_find_by.rb
@@ -0,0 +1,14 @@
+require "metamorpher"
+
+class RefactorWhereFirstToFindBy
+  include Metamorpher::Refactorer
+  include Metamorpher::Builders::Ruby
+
+  def pattern
+    builder.build("TYPE.where(PARAMS_).first")
+  end
+
+  def replacement
+    builder.build("TYPE.find_by(PARAMS_)")
+  end
+end