diff --git a/app/controllers/api/beta/participant_controller.rb b/app/controllers/api/beta/participant_controller.rb
index 9dcd19c22..0fb47402f 100644
--- a/app/controllers/api/beta/participant_controller.rb
+++ b/app/controllers/api/beta/participant_controller.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'course_list'
+
 class Api::Beta::ParticipantController < Api::Beta::BaseController
   before_action :doorkeeper_authorize!, scopes: [:public]
 
diff --git a/app/controllers/api/v8/base_controller.rb b/app/controllers/api/v8/base_controller.rb
index f8e633da1..a83f1c1c8 100644
--- a/app/controllers/api/v8/base_controller.rb
+++ b/app/controllers/api/v8/base_controller.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'json'
+require 'version'
 
 module Api
   module V8
diff --git a/app/controllers/api/v8/core/courses/reviews_controller.rb b/app/controllers/api/v8/core/courses/reviews_controller.rb
index b79fb2971..04e34df6a 100644
--- a/app/controllers/api/v8/core/courses/reviews_controller.rb
+++ b/app/controllers/api/v8/core/courses/reviews_controller.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'natsort'
+
 module Api
   module V8
     module Core
diff --git a/app/controllers/api/v8/core/exercises/submissions_controller.rb b/app/controllers/api/v8/core/exercises/submissions_controller.rb
index ea5f5f113..d7f808e4b 100644
--- a/app/controllers/api/v8/core/exercises/submissions_controller.rb
+++ b/app/controllers/api/v8/core/exercises/submissions_controller.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'submission_processor'
+
 module Api
   module V8
     module Core
diff --git a/app/controllers/api/v8/core/exercises_controller.rb b/app/controllers/api/v8/core/exercises_controller.rb
index 853b60ebe..dcc30ab66 100644
--- a/app/controllers/api/v8/core/exercises_controller.rb
+++ b/app/controllers/api/v8/core/exercises_controller.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'submission_list'
+
 module Api
   module V8
     module Core
diff --git a/app/controllers/api/v8/core/submissions/reviews_controller.rb b/app/controllers/api/v8/core/submissions/reviews_controller.rb
index dc74c0db8..8ccf4ab9f 100644
--- a/app/controllers/api/v8/core/submissions/reviews_controller.rb
+++ b/app/controllers/api/v8/core/submissions/reviews_controller.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'natsort'
+
 module Api
   module V8
     module Core
diff --git a/app/controllers/courses_controller.rb b/app/controllers/courses_controller.rb
index 406e15c0f..a9d446b39 100644
--- a/app/controllers/courses_controller.rb
+++ b/app/controllers/courses_controller.rb
@@ -4,6 +4,8 @@
 require 'course_list'
 require 'exercise_completion_status_generator'
 require 'json'
+require 'course_list'
+require 'course_info'
 
 class CoursesController < ApplicationController
   before_action :set_organization
diff --git a/app/controllers/exercises_controller.rb b/app/controllers/exercises_controller.rb
index b0d7d81c6..d9e634818 100644
--- a/app/controllers/exercises_controller.rb
+++ b/app/controllers/exercises_controller.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'submission_list'
+
 class ExercisesController < ApplicationController
   def show
     @exercise = Exercise.find(params[:id])
diff --git a/app/controllers/full_zip_controller.rb b/app/controllers/full_zip_controller.rb
index 8927da7a2..8988a5861 100644
--- a/app/controllers/full_zip_controller.rb
+++ b/app/controllers/full_zip_controller.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'submission_packager'
+
 class FullZipController < ApplicationController
   def index
     submission = Submission.find(params[:submission_id])
diff --git a/app/controllers/migrate_to_other_course_controller.rb b/app/controllers/migrate_to_other_course_controller.rb
index c293c84d0..861b8bedd 100644
--- a/app/controllers/migrate_to_other_course_controller.rb
+++ b/app/controllers/migrate_to_other_course_controller.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'student_submission_migrator'
+
 class MigrateToOtherCourseController < ApplicationController
   def show
     @old_course = Course.find(params[:course_id])
diff --git a/app/controllers/setup/course_details_controller.rb b/app/controllers/setup/course_details_controller.rb
index b1cd448e0..e46aa4c85 100644
--- a/app/controllers/setup/course_details_controller.rb
+++ b/app/controllers/setup/course_details_controller.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'course_refresh_database_updater'
+
 class Setup::CourseDetailsController < Setup::SetupController
   before_action :set_course, except: %i[new create]
 
diff --git a/app/models/course_template.rb b/app/models/course_template.rb
index ad3593746..9cae1c46c 100644
--- a/app/models/course_template.rb
+++ b/app/models/course_template.rb
@@ -3,6 +3,7 @@
 # Course stub to be copied by teachers for their own organisations
 
 require 'net/http'
+require 'system_commands'
 
 class CourseTemplate < ApplicationRecord
   include SystemCommands
diff --git a/app/models/deadline_spec.rb b/app/models/deadline_spec.rb
index 23d29336f..fe9eabd39 100644
--- a/app/models/deadline_spec.rb
+++ b/app/models/deadline_spec.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'date_and_time_utils'
+
 # Parses and abstracts specification in the "deadline" field of a `metadata.yml` file.
 class DeadlineSpec # (the name of this class is unfortunate as it confuses IDEs when jumping to tests)
   class InvalidSyntaxError < StandardError; end
diff --git a/app/models/exercise.rb b/app/models/exercise.rb
index a606f5e8e..303c17164 100644
--- a/app/models/exercise.rb
+++ b/app/models/exercise.rb
@@ -2,6 +2,8 @@
 
 require 'shellwords'
 
+require 'date_and_time_utils'
+
 class Exercise < ApplicationRecord
   self.include_root_in_json = false
   include Swagger::Blocks
diff --git a/app/models/submission.rb b/app/models/submission.rb
index 178f909de..2db931210 100644
--- a/app/models/submission.rb
+++ b/app/models/submission.rb
@@ -2,6 +2,7 @@
 
 require 'zlib'
 require 'securerandom'
+require 'submission_packager'
 
 class Submission < ApplicationRecord
   include Swagger::Blocks
diff --git a/app/models/unlock_spec.rb b/app/models/unlock_spec.rb
index 360e28694..31f9d373c 100644
--- a/app/models/unlock_spec.rb
+++ b/app/models/unlock_spec.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'date_and_time_utils'
+
 # Parses and abstracts specification in the "unlocked_after" field of a `metadata.yml` file.
 class UnlockSpec # (the name of this class is unfortunate as it confuses IDEs when jumping to tests)
   class InvalidSyntaxError < StandardError; end
diff --git a/config/site_tailoring.example.rb b/config/site_tailoring.example.rb
index 0a52f5328..20afcbed7 100644
--- a/config/site_tailoring.example.rb
+++ b/config/site_tailoring.example.rb
@@ -2,5 +2,7 @@
 
 # Optionally copy this file to site_tailoring.rb and
 # override methods defined in lib/tailoring.rb here.
+require 'tailoring'
+
 class SiteTailoring < Tailoring
 end
diff --git a/lib/course_info.rb b/lib/course_info.rb
index c03aec6bf..882390752 100644
--- a/lib/course_info.rb
+++ b/lib/course_info.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'natsort'
+require 'course_list'
 
 # Builds /courses/:id.json
 class CourseInfo
diff --git a/lib/course_list.rb b/lib/course_list.rb
index ef5f1c5c8..a0a608f08 100644
--- a/lib/course_list.rb
+++ b/lib/course_list.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'natsort'
+
 # Builds /courses.json
 class CourseList
   def initialize(user, helpers)
diff --git a/lib/course_refresh_database_updater.rb b/lib/course_refresh_database_updater.rb
index 95819bb76..ff9bc3ca9 100644
--- a/lib/course_refresh_database_updater.rb
+++ b/lib/course_refresh_database_updater.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'benchmark'
+require 'system_commands'
 
 class CourseRefreshDatabaseUpdater
   def refresh_course(course, refreshed_course_data)
diff --git a/lib/doc_gen/shell_session.rb b/lib/doc_gen/shell_session.rb
index 338e91d8b..99e2089fe 100644
--- a/lib/doc_gen/shell_session.rb
+++ b/lib/doc_gen/shell_session.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'cgi' # for escapeHTML
+require 'doc_gen'
 
 class DocGen
   # A shell session where the interaction can be printed to the generated document.
diff --git a/lib/sandbox_results_saver.rb b/lib/sandbox_results_saver.rb
index ff5663f94..1b978f829 100644
--- a/lib/sandbox_results_saver.rb
+++ b/lib/sandbox_results_saver.rb
@@ -3,6 +3,8 @@
 # Saves results from a remote sandbox to the database.
 #
 # See also: TestRunGrader
+require 'test_run_grader'
+
 module SandboxResultsSaver
   class InvalidTokenError < RuntimeError; end
 
diff --git a/lib/submission_packager.rb b/lib/submission_packager.rb
index bcb18abca..49df1f36d 100644
--- a/lib/submission_packager.rb
+++ b/lib/submission_packager.rb
@@ -2,6 +2,7 @@
 
 require 'tmpdir'
 require 'fileutils'
+require 'rust_langs_cli_executor'
 
 # Takes a submission zip and makes a tar file suitable for the sandbox
 class SubmissionPackager
diff --git a/spec/integration/admin_usecases_spec.rb b/spec/integration/admin_usecases_spec.rb
index 302ae5c4b..755b91075 100644
--- a/spec/integration/admin_usecases_spec.rb
+++ b/spec/integration/admin_usecases_spec.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
+require 'submission_processor'
 
 describe 'The system (used by an instructor for administration)', type: :request, integration: true do
   include IntegrationTestActions
diff --git a/spec/lib/course_refresh_database_updater_spec.rb b/spec/lib/course_refresh_database_updater_spec.rb
index 46e23bbce..5a27223b9 100644
--- a/spec/lib/course_refresh_database_updater_spec.rb
+++ b/spec/lib/course_refresh_database_updater_spec.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
+require 'course_refresh_database_updater'
 
 describe CourseRefreshDatabaseUpdater do
   include GitTestActions
diff --git a/spec/lib/date_and_time_utils_spec.rb b/spec/lib/date_and_time_utils_spec.rb
index 94eb20d20..c27f19b2f 100644
--- a/spec/lib/date_and_time_utils_spec.rb
+++ b/spec/lib/date_and_time_utils_spec.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
+require 'date_and_time_utils'
 
 describe DateAndTimeUtils do
   describe '#to_time' do
diff --git a/spec/lib/file_tree_hasher_spec.rb b/spec/lib/file_tree_hasher_spec.rb
index 572b61a81..58c7055b6 100644
--- a/spec/lib/file_tree_hasher_spec.rb
+++ b/spec/lib/file_tree_hasher_spec.rb
@@ -2,6 +2,7 @@
 
 require 'spec_helper'
 require 'fileutils'
+require 'file_tree_hasher'
 
 describe FileTreeHasher do
   def write_file(path, content)
diff --git a/spec/lib/submission_packager/java_maven_spec.rb b/spec/lib/submission_packager/java_maven_spec.rb
index ca73bf354..2c7b68492 100644
--- a/spec/lib/submission_packager/java_maven_spec.rb
+++ b/spec/lib/submission_packager/java_maven_spec.rb
@@ -4,6 +4,8 @@
 require 'tmpdir'
 require 'shellwords'
 require 'system_commands'
+require 'submission_packager'
+require 'rust_langs_cli_executor'
 
 # There is some functionality in common with JavaSimple. We mostly only test that in java_simple_spec.rb.
 describe SubmissionPackager do
diff --git a/spec/lib/submission_processor_spec.rb b/spec/lib/submission_processor_spec.rb
index a0685378c..3067d9869 100644
--- a/spec/lib/submission_processor_spec.rb
+++ b/spec/lib/submission_processor_spec.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
+require 'submission_processor'
 
 describe SubmissionProcessor do
   def expect_processing
diff --git a/spec/lib/test_run_grader_spec.rb b/spec/lib/test_run_grader_spec.rb
index 718dbf208..1033b6423 100644
--- a/spec/lib/test_run_grader_spec.rb
+++ b/spec/lib/test_run_grader_spec.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
+require 'test_run_grader'
 
 describe TestRunGrader do
   include GitTestActions
diff --git a/spec/lib/version_spec.rb b/spec/lib/version_spec.rb
index aa52dc14d..bf3976838 100644
--- a/spec/lib/version_spec.rb
+++ b/spec/lib/version_spec.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
+require 'version'
 
 describe Version do
   it 'splits the version string into components' do
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 9d8e3ea49..fcaa33273 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -9,6 +9,7 @@
 require 'fileutils'
 require 'capybara/poltergeist'
 require 'simplecov'
+require 'tailoring'
 # require 'rspec_remote_formatter'
 SimpleCov.start 'rails' do
   add_filter '/bin/'
diff --git a/spec/support/remote_sandbox_for_testing.rb b/spec/support/remote_sandbox_for_testing.rb
index 4a7b2e1e3..3d83d8c09 100644
--- a/spec/support/remote_sandbox_for_testing.rb
+++ b/spec/support/remote_sandbox_for_testing.rb
@@ -2,6 +2,7 @@
 
 require 'fileutils'
 require 'system_commands'
+require 'sandbox_results_saver'
 
 class RemoteSandboxForTesting
   @server_pids = nil
diff --git a/spec/usermanual/usermanual_spec.rb b/spec/usermanual/usermanual_spec.rb
index 989ee995a..e95d39933 100644
--- a/spec/usermanual/usermanual_spec.rb
+++ b/spec/usermanual/usermanual_spec.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
+require 'doc_gen'
 
 describe 'User manual', type: :request, usermanual: true, integration: true do
   def make_page(name)