diff --git a/Gemfile b/Gemfile
index 68e0b4aa2..ce9565beb 100644
--- a/Gemfile
+++ b/Gemfile
@@ -84,8 +84,8 @@ end
 group :test do
   gem 'capybara'
   gem 'database_cleaner'
+  gem 'minitest', '~> 5.14'
   gem 'simplecov', require: false
   gem 'webdrivers'
   gem 'webmock'
-  gem 'minitest', '~> 5.10.0'
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index ed210f681..75317c030 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -250,7 +250,7 @@ GEM
       rake
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    minitest (5.10.3)
+    minitest (5.14.0)
     monetize (1.9.4)
       money (~> 6.12)
     money (6.13.7)
@@ -479,7 +479,7 @@ DEPENDENCIES
   kaminari
   lhv!
   mina (= 0.3.1)
-  minitest (~> 5.10.0)
+  minitest (~> 5.14)
   money-rails
   nokogiri
   paper_trail (~> 4.0)
diff --git a/app/models/contact.rb b/app/models/contact.rb
index e4ed542a6..9cb954462 100644
--- a/app/models/contact.rb
+++ b/app/models/contact.rb
@@ -23,7 +23,9 @@ class Contact < ApplicationRecord
   accepts_nested_attributes_for :legal_documents
 
   validates :name, :email, presence: true
-  validates :street, :city, :zip, :country_code, presence: true, if: -> { self.class.address_processing? }
+  validates :street, :city, :zip, :country_code, presence: true, if: lambda {
+    self.class.address_processing?
+  }
 
   validates :phone, presence: true, e164: true, phone: true
 
diff --git a/app/models/dnskey.rb b/app/models/dnskey.rb
index 08a5b03d8..c0f3f7491 100644
--- a/app/models/dnskey.rb
+++ b/app/models/dnskey.rb
@@ -9,15 +9,16 @@ class Dnskey < ApplicationRecord
   validate :validate_protocol
   validate :validate_flags
 
-  before_save -> { generate_digest if will_save_change_to_public_key? &&
-                                      !will_save_change_to_ds_digest? }
+  before_save lambda {
+    generate_digest if will_save_change_to_public_key? && !will_save_change_to_ds_digest?
+  }
 
   before_save lambda {
     if (will_save_change_to_public_key? ||
         will_save_change_to_flags? ||
         will_save_change_to_alg? ||
         will_save_change_to_protocol?) &&
-        !will_save_change_to_ds_key_tag?
+       !will_save_change_to_ds_key_tag?
       generate_ds_key_tag
     end
   }
diff --git a/app/models/domain.rb b/app/models/domain.rb
index 3ad3b09f2..b37d31ea0 100644
--- a/app/models/domain.rb
+++ b/app/models/domain.rb
@@ -74,11 +74,12 @@ class Domain < ApplicationRecord
   before_update :manage_statuses
   def manage_statuses
     return unless will_save_change_to_registrant_id? # rollback has not yet happened
+
     pending_update! if registrant_verification_asked?
     true
   end
 
-  after_commit :update_whois_record, unless: 'domain_name.at_auction?'
+  after_commit :update_whois_record, unless: -> { domain_name.at_auction? }
 
   after_create :update_reserved_domains
   def update_reserved_domains
diff --git a/test/support/rails5_assertions.rb b/test/support/rails5_assertions.rb
deleted file mode 100644
index a11bb3ef1..000000000
--- a/test/support/rails5_assertions.rb
+++ /dev/null
@@ -1,96 +0,0 @@
-# Built-in since Rails 5.1
-
-module ActiveSupport
-  module Testing
-    module Assertions
-      UNTRACKED = Object.new # :nodoc:
-
-      # Assertion that the result of evaluating an expression is changed before
-      # and after invoking the passed in block.
-      #
-      #   assert_changes 'Status.all_good?' do
-      #     post :create, params: { status: { ok: false } }
-      #   end
-      #
-      # You can pass the block as a string to be evaluated in the context of
-      # the block. A lambda can be passed for the block as well.
-      #
-      #   assert_changes -> { Status.all_good? } do
-      #     post :create, params: { status: { ok: false } }
-      #   end
-      #
-      # The assertion is useful to test side effects. The passed block can be
-      # anything that can be converted to string with #to_s.
-      #
-      #   assert_changes :@object do
-      #     @object = 42
-      #   end
-      #
-      # The keyword arguments :from and :to can be given to specify the
-      # expected initial value and the expected value after the block was
-      # executed.
-      #
-      #   assert_changes :@object, from: nil, to: :foo do
-      #     @object = :foo
-      #   end
-      #
-      # An error message can be specified.
-      #
-      #   assert_changes -> { Status.all_good? }, 'Expected the status to be bad' do
-      #     post :create, params: { status: { incident: true } }
-      #   end
-      def assert_changes(expression, message = nil, from: UNTRACKED, to: UNTRACKED, &block)
-        exp = expression.respond_to?(:call) ? expression : -> { eval(expression.to_s, block.binding) }
-
-        before = exp.call
-        retval = yield
-
-        unless from == UNTRACKED
-          error = "#{expression.inspect} isn't #{from.inspect}"
-          error = "#{message}.\n#{error}" if message
-          assert from === before, error
-        end
-
-        after = exp.call
-
-        if to == UNTRACKED
-          error = "#{expression.inspect} didn't changed"
-          error = "#{message}.\n#{error}" if message
-          assert_not_equal before, after, error
-        else
-          error = "#{expression.inspect} didn't change to #{to}"
-          error = "#{message}.\n#{error}" if message
-          assert to === after, error
-        end
-
-        retval
-      end
-
-      # Assertion that the result of evaluating an expression is changed before
-      # and after invoking the passed in block.
-      #
-      #   assert_no_changes 'Status.all_good?' do
-      #     post :create, params: { status: { ok: true } }
-      #   end
-      #
-      # An error message can be specified.
-      #
-      #   assert_no_changes -> { Status.all_good? }, 'Expected the status to be good' do
-      #     post :create, params: { status: { ok: false } }
-      #   end
-      def assert_no_changes(expression, message = nil, &block)
-        exp = expression.respond_to?(:call) ? expression : -> { eval(expression.to_s, block.binding) }
-
-        before = exp.call
-        retval = yield
-        after = exp.call
-
-        error = "#{expression.inspect} did change to #{after}"
-        error = "#{message}.\n#{error}" if message
-        assert_equal before, after, error
-
-        retval
-      end
-    end
-  end
-end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 4cd632ea2..efdbc288f 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -16,7 +16,6 @@ require 'minitest/mock'
 require 'capybara/rails'
 require 'capybara/minitest'
 require 'webmock/minitest'
-require 'support/rails5_assertions' # Remove once upgraded to Rails 5.1
 require 'support/assertions/epp_assertions'