diff --git a/Library/Homebrew/test/test_migrator.rb b/Library/Homebrew/test/test_migrator.rb
new file mode 100644
index 0000000000000000000000000000000000000000..b22184888fac2ee5df16508326c4e780fc4852d6
--- /dev/null
+++ b/Library/Homebrew/test/test_migrator.rb
@@ -0,0 +1,268 @@
+require "testing_env"
+require "migrator"
+require "testball"
+require "tab"
+require "keg"
+
+class Formula
+  def set_oldname oldname
+    @oldname = oldname
+  end
+end
+
+class MigratorErrorsTests < Homebrew::TestCase
+  def setup
+    @new_f = Testball.new("newname")
+    @new_f.set_oldname "oldname"
+    @old_f = Testball.new("oldname")
+  end
+
+  def test_no_oldname
+    assert_raises(Migrator::MigratorNoOldnameError) { Migrator.new(@old_f) }
+  end
+
+  def test_no_oldpath
+    assert_raises(Migrator::MigratorNoOldpathError) { Migrator.new(@new_f) }
+  end
+
+  def test_different_taps
+    keg = HOMEBREW_CELLAR/"oldname/0.1"
+    keg.mkpath
+    tab = Tab.empty
+    tab.tabfile = HOMEBREW_CELLAR/"oldname/0.1/INSTALL_RECEIPT.json"
+    tab.source["tap"] = "Homebrew/homebrew"
+    tab.write
+    assert_raises(Migrator::MigratorDifferentTapsError) { Migrator.new(@new_f) }
+  ensure
+    keg.parent.rmtree
+  end
+end
+
+class MigratorTests < Homebrew::TestCase
+  include FileUtils
+
+  def setup
+    @new_f = Testball.new("newname")
+    @new_f.set_oldname "oldname"
+
+    @old_f = Testball.new("oldname")
+
+    @old_keg_record = HOMEBREW_CELLAR/"oldname/0.1"
+    @old_keg_record.join("bin").mkpath
+    @new_keg_record = HOMEBREW_CELLAR/"newname/0.1"
+
+    %w[inside bindir].each { |file| touch @old_keg_record.join("bin", file) }
+
+    @old_tab = Tab.empty
+    @old_tab.tabfile = HOMEBREW_CELLAR/"oldname/0.1/INSTALL_RECEIPT.json"
+    @old_tab.source["path"] = "/oldname"
+    @old_tab.write
+
+    @keg = Keg.new(@old_keg_record)
+    @keg.link
+    @keg.optlink
+
+    @old_pin = HOMEBREW_LIBRARY/"PinnedKegs/oldname"
+    @old_pin.make_relative_symlink @old_keg_record
+
+    @migrator = Migrator.new(@new_f)
+
+    mkpath HOMEBREW_PREFIX/"bin"
+  end
+
+  def teardown
+    @old_pin.unlink if @old_pin.symlink?
+
+    if @old_keg_record.parent.symlink?
+      @old_keg_record.parent.unlink
+    elsif @old_keg_record.directory?
+      @keg.unlink
+      @keg.uninstall
+    end
+
+    if @new_keg_record.directory?
+      new_keg = Keg.new(@new_keg_record)
+      new_keg.unlink
+      new_keg.uninstall
+    end
+
+    @old_keg_record.parent.rmtree if @old_keg_record.parent.directory?
+    @new_keg_record.parent.rmtree if @new_keg_record.parent.directory?
+
+    rmtree HOMEBREW_PREFIX/"bin"
+    rmtree HOMEBREW_PREFIX/"opt" if (HOMEBREW_PREFIX/"opt").directory?
+    # What to do with pin?
+    @new_f.unpin
+  end
+
+  def test_move_cellar
+    @keg.unlink
+    shutup { @migrator.move_to_new_directory }
+    assert_predicate @new_keg_record, :directory?
+    assert_predicate @new_keg_record/"bin", :directory?
+    assert_predicate @new_keg_record/"bin/inside", :file?
+    assert_predicate @new_keg_record/"bin/bindir", :file?
+    refute_predicate @old_keg_record, :directory?
+  end
+
+  def test_backup_cellar
+    @old_keg_record.parent.rmtree
+    @new_keg_record.join("bin").mkpath
+
+    @migrator.backup_oldname_cellar
+
+    assert_predicate @old_keg_record, :directory?
+    assert_predicate @old_keg_record/"bin", :directory?
+  end
+
+  def test_oldkeg_linked
+    assert_predicate @migrator, :oldkeg_linked?
+  end
+
+  def test_repin
+    @new_keg_record.join("bin").mkpath
+    expected_relative = @new_keg_record.relative_path_from HOMEBREW_LIBRARY/"PinnedKegs"
+
+    @migrator.repin
+
+    assert_predicate @migrator.new_pin_record, :symlink?
+    assert_equal expected_relative, @migrator.new_pin_record.readlink
+    refute_predicate @migrator.old_pin_record, :exist?
+  end
+
+  def test_unlink_oldname
+    assert_equal 1, HOMEBREW_LIBRARY.join("LinkedKegs").children.size
+    assert_equal 1, HOMEBREW_PREFIX.join("opt").children.size
+
+    shutup { @migrator.unlink_oldname }
+
+    refute_predicate HOMEBREW_LIBRARY/"LinkedKegs", :exist?
+    refute_predicate HOMEBREW_LIBRARY.join("bin"), :exist?
+  end
+
+  def test_link_newname
+    @keg.unlink
+    @keg.uninstall
+    @new_keg_record.join("bin").mkpath
+    %w[inside bindir].each { |file| touch @new_keg_record.join("bin", file) }
+
+    shutup { @migrator.link_newname }
+
+    assert_equal 1, HOMEBREW_LIBRARY.join("LinkedKegs").children.size
+    assert_equal 1, HOMEBREW_PREFIX.join("opt").children.size
+  end
+
+  def test_link_oldname_opt
+    @new_keg_record.mkpath
+    @migrator.link_oldname_opt
+    assert_equal @new_keg_record.realpath, (HOMEBREW_PREFIX/"opt/oldname").realpath
+  end
+
+  def test_link_oldname_cellar
+    @new_keg_record.join("bin").mkpath
+    @keg.unlink
+    @keg.uninstall
+    @migrator.link_oldname_cellar
+    assert_equal @new_keg_record.parent.realpath, (HOMEBREW_CELLAR/"oldname").realpath
+  end
+
+  def test_update_tabs
+    @new_keg_record.join("bin").mkpath
+    tab = Tab.empty
+    tab.tabfile = HOMEBREW_CELLAR/"newname/0.1/INSTALL_RECEIPT.json"
+    tab.source["path"] = "/path/that/must/be/changed/by/update_tabs"
+    tab.write
+    @migrator.update_tabs
+    assert_equal @new_f.path.to_s, Tab.for_keg(@new_keg_record).source["path"]
+  end
+
+  def test_migrate
+    tab = Tab.empty
+    tab.tabfile = HOMEBREW_CELLAR/"oldname/0.1/INSTALL_RECEIPT.json"
+    tab.source["path"] = @old_f.path.to_s
+    tab.write
+
+    shutup { @migrator.migrate }
+
+    assert_predicate @new_keg_record, :exist?
+    assert_predicate @old_keg_record.parent, :symlink?
+    refute_predicate (HOMEBREW_LIBRARY/"LinkedKegs/oldname"), :exist?
+    assert_equal @new_keg_record.realpath, (HOMEBREW_LIBRARY/"LinkedKegs/newname").realpath
+    assert_equal @new_keg_record.realpath, @old_keg_record.realpath
+    assert_equal @new_keg_record.realpath, (HOMEBREW_PREFIX/"opt/oldname").realpath
+    assert_equal @new_keg_record.parent.realpath, (HOMEBREW_CELLAR/"oldname").realpath
+    assert_equal @new_keg_record.realpath, (HOMEBREW_LIBRARY/"PinnedKegs/newname").realpath
+    assert_equal @new_f.path.to_s, Tab.for_keg(@new_keg_record).source["path"]
+  end
+
+  def test_unlinik_oldname_opt
+    @new_keg_record.mkpath
+    old_opt_record = HOMEBREW_PREFIX/"opt/oldname"
+    old_opt_record.unlink if old_opt_record.symlink?
+    old_opt_record.make_relative_symlink(@new_keg_record)
+    @migrator.unlink_oldname_opt
+    refute_predicate old_opt_record, :symlink?
+  end
+
+  def test_unlink_oldname_cellar
+    @new_keg_record.mkpath
+    @keg.unlink
+    @keg.uninstall
+    @old_keg_record.parent.make_relative_symlink(@new_keg_record.parent)
+    @migrator.unlink_oldname_cellar
+    refute_predicate @old_keg_record.parent, :symlink?
+  end
+
+  def test_backup_oldname_cellar
+    @new_keg_record.join("bin").mkpath
+    @keg.unlink
+    @keg.uninstall
+    @migrator.backup_oldname_cellar
+    refute_predicate @old_keg_record.subdirs, :empty?
+  end
+
+  def test_backup_old_tabs
+    tab = Tab.empty
+    tab.tabfile = HOMEBREW_CELLAR/"oldname/0.1/INSTALL_RECEIPT.json"
+    tab.source["path"] = "/should/be/the/same"
+    tab.write
+    migrator = Migrator.new(@new_f)
+    tab.tabfile.delete
+    migrator.backup_old_tabs
+    assert_equal "/should/be/the/same", Tab.for_keg(@old_keg_record).source["path"]
+  end
+
+  # Backup tests are divided into three groups: when oldname Cellar is deleted
+  # and when it still exists and when it's a symlink
+
+  def check_after_backup
+    assert_predicate @old_keg_record.parent, :directory?
+    refute_predicate @old_keg_record.parent.subdirs, :empty?
+    assert_predicate HOMEBREW_LIBRARY/"LinkedKegs/oldname", :exist?
+    assert_predicate HOMEBREW_PREFIX/"opt/oldname", :exist?
+    assert_predicate HOMEBREW_LIBRARY/"PinnedKegs/oldname", :symlink?
+    assert_predicate @keg, :linked?
+  end
+
+  def test_backup_cellar_exist
+    @migrator.backup_oldname
+    check_after_backup
+  end
+
+  def test_backup_cellar_removed
+    @new_keg_record.join("bin").mkpath
+    @keg.unlink
+    @keg.uninstall
+    @migrator.backup_oldname
+    check_after_backup
+  end
+
+  def test_backup_cellar_linked
+    @new_keg_record.join("bin").mkpath
+    @keg.unlink
+    @keg.uninstall
+    @old_keg_record.parent.make_relative_symlink(@new_keg_record.parent)
+    @migrator.backup_oldname
+    check_after_backup
+  end
+end