diff --git a/.config/.codecov.yml b/.config/.codecov.yml
new file mode 100644
index 000000000..9e14ade12
--- /dev/null
+++ b/.config/.codecov.yml
@@ -0,0 +1,5 @@
+# Ignore test files themselves in the Codecov report
+# see: https://about.codecov.io/blog/should-i-include-test-files-in-code-coverage-calculations/
+ignore:
+  - "spec/"
+  - "*_spec.rb"
diff --git a/.dockerignore b/.dockerignore
deleted file mode 100644
index 844014fb0..000000000
--- a/.dockerignore
+++ /dev/null
@@ -1,9 +0,0 @@
-docker/developement/docker-compose.yml
-docker/developement/Dockerfile
-docker/run_tests/docker-compose.yml
-docker/run_tests/Dockerfile
-**/.git
-LICENSE
-README.md
-mampf-gui-transparent.png
-.dockerignore
diff --git a/.github/workflows/docker-compose-cache.json b/.github/workflows/docker-compose-cache.json
new file mode 100644
index 000000000..baee2cfd8
--- /dev/null
+++ b/.github/workflows/docker-compose-cache.json
@@ -0,0 +1,15 @@
+{
+  "target": {
+    "mampf": {
+      "cache-from": [
+        "type=registry,ref=ghcr.io/mampf-hd/mampf:cache"
+      ],
+      "cache-to": [
+        "type=registry,ref=ghcr.io/mampf-hd/mampf:cache"
+      ],
+      "output": [
+        "type=docker"
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 000000000..db47d5027
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,62 @@
+name: Testing
+
+on:
+  push:
+    branches:
+      - main
+      - dev
+      - experimental
+  pull_request:
+    types: [opened, reopened, synchronize, ready_for_review]
+
+jobs:
+  # For the setup idea using Docker Buildx, see StackOverflow answer [1].
+  # [2] and [3] might also be very useful. [4] is generally about Docker
+  # cache management within GitHub Actions.
+  #
+  # [1] https://stackoverflow.com/a/75544124/
+  # [2] https://depot.dev/blog/docker-layer-caching-in-github-actions#docker-layer-caching-in-github-actions
+  # [3] https://www.deploysentinel.com/blog/docker-buildx-cache-with-github-actions
+  # [4] https://docs.docker.com/build/ci/github-actions/cache/
+  unit-tests:
+    name: Unit tests
+    environment: testing
+    runs-on: ubuntu-latest
+    permissions: write-all
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+            submodules: recursive
+
+      - name: Setup Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      # see https://github.com/orgs/MaMpf-HD/packages?repo_name=mampf
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build docker images
+        # As the docker-compose.yml file uses contexts like "./../..", we have
+        # to change the working directory here.
+        working-directory: docker/test
+        run: |
+          docker buildx bake --file ./docker-compose.yml --file ./../../.github/workflows/docker-compose-cache.json
+
+      - name: Run unit tests
+        working-directory: docker/test
+        run: |
+          docker compose run --entrypoint="" mampf sh -c "RAILS_ENV=test bundle exec rspec --format RSpec::Github::Formatter"
+
+      - name: Report test coverage to codecov
+        uses: codecov/codecov-action@v4
+        with:
+          fail_ci_if_error: true
+          files: ./coverage/coverage.xml
+          token: ${{ secrets.CODECOV_TOKEN }}
+          verbose: true
+          codecov_yml_path: ./config/codecov.yml
diff --git a/.vscode/settings.json b/.vscode/settings.json
index 473af2bd1..9dcca743d 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -55,6 +55,16 @@
     },
     "rubyLsp.enableExperimentalFeatures": true,
     //////////////////////////////////////
+    // Ruby Test Explorer
+    //////////////////////////////////////
+    "rubyTestExplorer.testFramework": "rspec",
+    "rubyTestExplorer.rspecCommand": "python3 ./spec/rspec_inside_docker.py",
+    "rubyTestExplorer.rspecDirectory": "./spec/",
+    "rubyTestExplorer.logpanel": true,
+    "rubyTestExplorer.filePattern": [
+        "*_spec.rb"
+    ],
+    //////////////////////////////////////
     // Files
     //////////////////////////////////////
     "files.exclude": {
diff --git a/Gemfile b/Gemfile
index 0e7992715..d300a1561 100644
--- a/Gemfile
+++ b/Gemfile
@@ -123,7 +123,7 @@ group :test do
   # Adds support for Capybara system testing and selenium driver
   gem "selenium-webdriver"
   # Easy installation and use of web drivers to run system tests with browsers
-  gem "database_cleaner"
+  gem "database_cleaner-active_record"
   gem "faker"
   gem "launchy"
   gem "simplecov", require: false
@@ -138,6 +138,8 @@ group :test, :development, :docker_development do
 
   gem "cypress-on-rails", "~> 1.0"
   gem "simplecov-cobertura"
+
+  gem "rspec-github"
 end
 
 gem "prometheus_exporter"
diff --git a/Gemfile.lock b/Gemfile.lock
index 651f9feff..bb7841bd3 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -187,8 +187,6 @@ GEM
     cypress-on-rails (1.17.0)
       rack
     dalli (3.2.8)
-    database_cleaner (2.0.2)
-      database_cleaner-active_record (>= 2, < 3)
     database_cleaner-active_record (2.1.0)
       activerecord (>= 5.a)
       database_cleaner-core (~> 2.0.0)
@@ -497,6 +495,8 @@ GEM
     rspec-expectations (3.13.0)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
+    rspec-github (2.4.0)
+      rspec-core (~> 3.0)
     rspec-mocks (3.13.0)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
@@ -686,7 +686,7 @@ DEPENDENCIES
   coveralls
   cypress-on-rails (~> 1.0)
   dalli (>= 2.7)
-  database_cleaner
+  database_cleaner-active_record
   devise
   devise-bootstrap-views
   erubis
@@ -726,6 +726,7 @@ DEPENDENCIES
   responders
   rgl
   rqrcode
+  rspec-github
   rspec-rails
   rubocop (~> 1.63)
   rubocop-performance (~> 1.21)
diff --git a/config/webpack/test.js b/config/webpack/test.js
index 7f3342f96..b95b8458c 100644
--- a/config/webpack/test.js
+++ b/config/webpack/test.js
@@ -1,4 +1,4 @@
-process.env.NODE_ENV = process.env.NODE_ENV || "development";
+process.env.NODE_ENV = process.env.NODE_ENV || "test";
 
 const environment = require("./environment");
 
diff --git a/docker/run_cypress_tests/Dockerfile b/docker/test/Dockerfile
similarity index 92%
rename from docker/run_cypress_tests/Dockerfile
rename to docker/test/Dockerfile
index f37415d1a..74cdc9b38 100644
--- a/docker/run_cypress_tests/Dockerfile
+++ b/docker/test/Dockerfile
@@ -66,5 +66,8 @@ RUN yarn install --production=false
 COPY --from=build-pdfcomprezzor /go/src/pdfcomprezzor.wasm /go/src/wasm_exec.js /usr/src/app/public/pdfcomprezzor/
 COPY --from=build-pdfcomprezzor /go/src/pdfcomprezzor.wasm /go/src/wasm_exec.js /
 
-COPY  ./ /usr/src/app/
-RUN RAILS_ENV=test TEST_DATABASE_ADAPTER=postgresql rake assets:precompile
+COPY . /usr/src/app/
+COPY ./docker/production/docker.env ./docker-dummy.env
+
+RUN set -o allexport && . ./docker-dummy.env && set +o allexport && \
+    RAILS_ENV=test TEST_DATABASE_ADAPTER=nulldb bundle exec rails assets:precompile
diff --git a/docker/run_cypress_tests/Dockerfile_cypress b/docker/test/Dockerfile_cypress
similarity index 100%
rename from docker/run_cypress_tests/Dockerfile_cypress
rename to docker/test/Dockerfile_cypress
diff --git a/docker/run_cypress_tests/docker-compose.local.yml b/docker/test/docker-compose.local.yml
similarity index 93%
rename from docker/run_cypress_tests/docker-compose.local.yml
rename to docker/test/docker-compose.local.yml
index 83c57390a..1b151338c 100644
--- a/docker/run_cypress_tests/docker-compose.local.yml
+++ b/docker/test/docker-compose.local.yml
@@ -30,12 +30,12 @@ services:
   mampf:
     build:
       context: ./../..
-      dockerfile: docker/run_cypress_tests/Dockerfile
+      dockerfile: docker/test/Dockerfile
     image: mampf:tests
     ports:
       - "127.0.0.1:3000:3000"
     # TODO: Use this
-    # entrypoint: /usr/src/app/docker/run_cypress_tests/run_tests.sh
+    # entrypoint: /usr/src/app/docker/test/run_tests.sh
     entrypoint: ./entrypoint.sh
     environment:
       RAILS_ENV: test
@@ -76,7 +76,7 @@ services:
     image: mampf-cypress
     build:
       context: ./../..
-      dockerfile: docker/run_cypress_tests/Dockerfile_cypress
+      dockerfile: docker/test/Dockerfile_cypress
     environment:
       CYPRESS_baseUrl: http://mampf:3000
     entrypoint: bash -c "while ! curl -s $$CYPRESS_baseUrl > /dev/null; do echo waiting for MaMpf to come online at $$CYPRESS_baseUrl; sleep 1; done; npx cypress run $$@"
diff --git a/docker/run_cypress_tests/docker-compose.yml b/docker/test/docker-compose.yml
similarity index 70%
rename from docker/run_cypress_tests/docker-compose.yml
rename to docker/test/docker-compose.yml
index e4a8d5139..23e00fb3c 100644
--- a/docker/run_cypress_tests/docker-compose.yml
+++ b/docker/test/docker-compose.yml
@@ -33,13 +33,14 @@ services:
     image: dockage/mailcatcher:latest
     networks:
       - backend
+
   mampf:
     build:
       context: ./../..
-      dockerfile: docker/run_cypress_tests/Dockerfile
+      dockerfile: docker/test/Dockerfile
     image: mampf:tests
     # TODO: Use this
-    # entrypoint: /usr/src/app/docker/run_cypress_tests/run_tests.sh
+    # entrypoint: /usr/src/app/docker/test/run_tests.sh
     entrypoint: /usr/src/app/entrypoint.sh
     environment:
       RAILS_ENV: test
@@ -58,14 +59,16 @@ services:
       ERDBEERE_API: https://erdbeere.mathi.uni-heidelberg.de/api/v1
       MUESLI_SERVER: https://muesli.mathi.uni-heidelberg.de
       PROJECT_EMAIL: project@localhost
-      FEEBACK_EMAIL: feedback@localhost
+      FEEDBACK_EMAIL: feedback@localhost
       PROJECT_NOTIFICATION_EMAIL: project+notification@localhost
+      ERROR_EMAIL: mampf-error@localhost
       MEDIA_FOLDER: mampf
       REDIS_URL: redis://redis:6379/1
       SOLR_HOST: solr
       SOLR_PORT: 8983
       SOLR_PATH: /solr/test
       SPROCKETS_CACHE: /cache
+      BLOG: https://mampf.blog
     volumes:
         - type: bind
           source: ../../spec/
@@ -79,23 +82,3 @@ services:
     networks:
       - backend
       - frontend
-
-  cypress_runner:
-    image: mampf-cypress
-    build:
-      context: ./../..
-      dockerfile: docker/run_cypress_tests/Dockerfile_cypress
-    environment:
-      CYPRESS_baseUrl: http://mampf:3000
-    volumes:
-      - ../../spec/cypress/e2e:/cypress/e2e:ro
-      - ../../spec/cypress/fixtures:/cypress/fixtures:ro
-      - ../../spec/cypress.config.js:/cypress.config.js:ro
-      - ../../.git:/.git:ro
-      # cypress outputs are saved here (needed only locally)
-      #- ../../cypress/videos:/cypress/videos
-      #- ../../cypress/screenshots:/cypress/screenshots
-    depends_on:
-      - mampf
-    networks:
-      - frontend
diff --git a/docker/run_cypress_tests/run_tests.sh b/docker/test/run_tests.sh
similarity index 100%
rename from docker/run_cypress_tests/run_tests.sh
rename to docker/test/run_tests.sh
diff --git a/spec/factories/users.rb b/spec/factories/users.rb
index c4b8dbbc7..b9affdd33 100644
--- a/spec/factories/users.rb
+++ b/spec/factories/users.rb
@@ -35,5 +35,11 @@
     factory :confirmed_user, traits: [:skip_confirmation_notification,
                                       :auto_confirmed,
                                       :consented]
+
+    factory :confirmed_user_en, traits: [:skip_confirmation_notification,
+                                         :auto_confirmed,
+                                         :consented] do
+      locale { "en" }
+    end
   end
 end
diff --git a/spec/models/announcement_spec.rb b/spec/models/announcement_spec.rb
index 7d5112ae3..a021f9997 100644
--- a/spec/models/announcement_spec.rb
+++ b/spec/models/announcement_spec.rb
@@ -16,7 +16,7 @@
   # test traits
 
   describe "with lecture" do
-    before :all do
+    before :each do
       @announcement = FactoryBot.build(:announcement, :with_lecture)
     end
     it "has a valid factory" do
diff --git a/spec/models/answer_spec.rb b/spec/models/answer_spec.rb
index b8211e4e5..7342306bf 100644
--- a/spec/models/answer_spec.rb
+++ b/spec/models/answer_spec.rb
@@ -15,7 +15,7 @@
   # test traits
 
   describe "with stuff" do
-    before :all do
+    before :each do
       @answer = FactoryBot.build(:answer, :with_stuff)
     end
     it "has a text" do
diff --git a/spec/models/chapter_spec.rb b/spec/models/chapter_spec.rb
index af3a1a262..4630bf445 100644
--- a/spec/models/chapter_spec.rb
+++ b/spec/models/chapter_spec.rb
@@ -15,7 +15,7 @@
   # test traits
 
   describe "chapter with sections" do
-    before :all do
+    before :each do
       @chapter = FactoryBot.build(:chapter, :with_sections)
     end
     it "has a valid factory" do
diff --git a/spec/models/consumption_spec.rb b/spec/models/consumption_spec.rb
index 698776175..9b80fe8f3 100644
--- a/spec/models/consumption_spec.rb
+++ b/spec/models/consumption_spec.rb
@@ -8,7 +8,7 @@
   # describe traits
 
   describe "with stuff" do
-    before :all do
+    before :each do
       @consumption = FactoryBot.build(:consumption, :with_stuff)
     end
     it "has a medium id" do
diff --git a/spec/models/course_spec.rb b/spec/models/course_spec.rb
index 46165b833..353fe81db 100644
--- a/spec/models/course_spec.rb
+++ b/spec/models/course_spec.rb
@@ -29,7 +29,7 @@
   # Test traits
 
   describe "course with tags" do
-    before :all do
+    before :each do
       @course = FactoryBot.build(:course, :with_tags)
     end
     it "has a valid factory" do
@@ -98,7 +98,7 @@
   # test callbacks
 
   describe "after save" do
-    before :all do
+    before :each do
       @course = FactoryBot.create(:course)
       @lecture = FactoryBot.create(:lecture_with_sparse_toc, course: @course)
       @lesson = FactoryBot.create(:valid_lesson, lecture: @lecture)
@@ -283,7 +283,7 @@
   end
 
   context "subscribable lectures" do
-    before :all do
+    before :each do
       @admin = FactoryBot.create(:confirmed_user, admin: true)
       @course_editor = FactoryBot.create(:confirmed_user)
       @editor = FactoryBot.create(:confirmed_user)
@@ -334,7 +334,7 @@
   end
 
   context "lecture sorting" do
-    before :all do
+    before :each do
       @course = FactoryBot.create(:course)
       year = Faker::Number.between(from: 1_000_001, to: 100_000_000)
       term1 = FactoryBot.create(:term, year: year, season: "SS")
@@ -383,7 +383,7 @@
   end
 
   context "lecture subscriptions" do
-    before :all do
+    before :each do
       @course = FactoryBot.create(:course)
       year = Faker::Number.between(from: 1_000_001, to: 100_000_000)
       term1 = FactoryBot.create(:term, year: year, season: "SS")
@@ -436,7 +436,7 @@
   end
 
   describe "#edited_by?" do
-    before :all do
+    before :each do
       @user = FactoryBot.create(:confirmed_user)
     end
 
@@ -495,7 +495,7 @@
   end
 
   describe "#removable_by?" do
-    before :all do
+    before :each do
       @user = FactoryBot.create(:confirmed_user)
     end
 
@@ -511,7 +511,7 @@
   end
 
   context "media and their items with inheritance" do
-    before :all do
+    before :each do
       @course = FactoryBot.create(:course, short_title: "LA2")
       term = FactoryBot.create(:term, year: 2020, season: "SS")
       lecture = FactoryBot.create(:lecture_with_sparse_toc, course: @course,
@@ -576,7 +576,7 @@
   end
 
   context "class methods for select forms" do
-    before :all do
+    before :each do
       Course.destroy_all
       @user = FactoryBot.create(:confirmed_user)
       @admin = FactoryBot.create(:confirmed_user, admin: true)
@@ -644,7 +644,7 @@
   end
 
   context "complex question methods" do
-    before :all do
+    before :each do
       @course = FactoryBot.create(:course)
       @lecture1 = FactoryBot.create(:lecture, :released_for_all,
                                     course: @course)
@@ -812,7 +812,7 @@
   end
 
   context "image methods" do
-    before :all do
+    before :each do
       @course = FactoryBot.create(:course, :with_image)
     end
 
@@ -884,7 +884,7 @@
   end
 
   describe "self.similar_courses" do
-    before :all do
+    before :each do
       Course.destroy_all
       @course1 = FactoryBot.create(:course, title: "Algebra 1")
       @course2 = FactoryBot.create(:course, title: "Algebra 2")
@@ -908,7 +908,7 @@
   end
 
   describe "#search_by" do
-    before :all do
+    before :each do
       Course.destroy_all
       @editor1 = FactoryBot.create(:confirmed_user)
       @editor2 = FactoryBot.create(:confirmed_user)
diff --git a/spec/models/interaction_spec.rb b/spec/models/interaction_spec.rb
index d42264c37..3e355b1e2 100644
--- a/spec/models/interaction_spec.rb
+++ b/spec/models/interaction_spec.rb
@@ -8,7 +8,7 @@
   # describe traits
 
   describe "with stuff" do
-    before :all do
+    before :each do
       @interaction = FactoryBot.build(:interaction, :with_stuff)
     end
     it "has a session id" do
diff --git a/spec/models/lecture_spec.rb b/spec/models/lecture_spec.rb
index 26d67fbdb..d2ba05682 100644
--- a/spec/models/lecture_spec.rb
+++ b/spec/models/lecture_spec.rb
@@ -28,7 +28,7 @@
   # Test traits
 
   describe "lecture with organizational stuff" do
-    before :all do
+    before :each do
       @lecture = FactoryBot.build(:lecture, :with_organizational_stuff)
     end
     it "has a valid factory" do
@@ -42,7 +42,7 @@
     end
   end
   describe "lecture which is released for all" do
-    before :all do
+    before :each do
       @lecture = FactoryBot.build(:lecture, :released_for_all)
     end
     it "has a valid factory" do
@@ -53,7 +53,7 @@
     end
   end
   describe "term independent lecture" do
-    before :all do
+    before :each do
       @lecture = FactoryBot.build(:lecture, :term_independent)
     end
     it "has a valid factory" do
@@ -64,7 +64,7 @@
     end
   end
   describe "with table of contents" do
-    before :all do
+    before :each do
       @lecture = FactoryBot.build(:lecture, :with_toc)
     end
     it "has 3 chapters" do
@@ -75,7 +75,7 @@
     end
   end
   describe "with sparse table of contents" do
-    before :all do
+    before :each do
       @lecture = FactoryBot.build(:lecture, :with_sparse_toc)
     end
     it "has one chapter" do
diff --git a/spec/models/medium_publisher_spec.rb b/spec/models/medium_publisher_spec.rb
index 62f3665ae..1b5f4ae98 100644
--- a/spec/models/medium_publisher_spec.rb
+++ b/spec/models/medium_publisher_spec.rb
@@ -13,7 +13,7 @@
   end
 
   describe "::parse" do
-    before :all do
+    before :each do
       @medium = FactoryBot.create(:lecture_medium)
       @user = FactoryBot.create(:confirmed_user)
     end
@@ -79,7 +79,7 @@
 
   describe "#publish!" do
     context "without extra stuff" do
-      before :all do
+      before :each do
         @medium = FactoryBot.create(:lecture_medium)
         lecture = @medium.teachable
         lecture.update(released: "all")
@@ -160,7 +160,7 @@
   end
 
   describe "#assignment" do
-    before :all do
+    before :each do
       @medium = FactoryBot.create(:lecture_medium)
       @lecture = @medium.teachable
       user = FactoryBot.create(:confirmed_user)
@@ -192,7 +192,7 @@
   end
 
   describe "#errors" do
-    before :all do
+    before :each do
       @medium = FactoryBot.create(:lecture_medium)
       @user = FactoryBot.create(:confirmed_user)
     end
diff --git a/spec/models/medium_spec.rb b/spec/models/medium_spec.rb
index 2fca9e938..371cb2d80 100644
--- a/spec/models/medium_spec.rb
+++ b/spec/models/medium_spec.rb
@@ -95,7 +95,7 @@
   end
 
   describe "lesson medium" do
-    before :all do
+    before :each do
       @medium = FactoryBot.build(:lesson_medium)
     end
     it "has a valid factory" do
@@ -110,7 +110,7 @@
   end
 
   describe "lecture medium" do
-    before :all do
+    before :each do
       @medium = FactoryBot.build(:lecture_medium)
     end
     it "has a valid factory" do
@@ -125,7 +125,7 @@
   end
 
   describe "course medium" do
-    before :all do
+    before :each do
       @medium = FactoryBot.build(:course_medium)
     end
     it "has a valid factory" do
diff --git a/spec/models/notion_spec.rb b/spec/models/notion_spec.rb
index 31c6fa334..4d79da4a9 100644
--- a/spec/models/notion_spec.rb
+++ b/spec/models/notion_spec.rb
@@ -24,7 +24,7 @@
   # test traits
 
   describe "notion with tag" do
-    before :all do
+    before :each do
       @notion = FactoryBot.build(:notion, :with_tag)
     end
     it "has a valid factory" do
diff --git a/spec/models/probe_spec.rb b/spec/models/probe_spec.rb
index 59a567d97..e0f7bfa10 100644
--- a/spec/models/probe_spec.rb
+++ b/spec/models/probe_spec.rb
@@ -8,7 +8,7 @@
   # describe traits
 
   describe "with stuff" do
-    before :all do
+    before :each do
       @probe = FactoryBot.build(:probe, :with_stuff)
     end
     it "has a question id" do
diff --git a/spec/models/question_sampler_spec.rb b/spec/models/question_sampler_spec.rb
index 51ad1425f..4c1a3e820 100644
--- a/spec/models/question_sampler_spec.rb
+++ b/spec/models/question_sampler_spec.rb
@@ -1,10 +1,12 @@
+require "rails_helper"
+
 RSpec.describe(QuestionSampler, type: :model) do
   it "has a valid factory" do
     expect(FactoryBot.build(:question_sampler)).to be_kind_of(QuestionSampler)
   end
 
   describe "#sample!" do
-    before :all do
+    before :each do
       @questions = Question.where(id: FactoryBot.create_list(:valid_question, 4)
                                                 .map(&:id))
     end
@@ -28,7 +30,7 @@
     end
 
     context "in a simple example" do
-      before :all do
+      before :each do
         tags = Tag.where(id: FactoryBot.create_list(:tag, 3).map(&:id))
         @questions[0].tags << tags[0]
         @questions[1].tags << tags[1]
diff --git a/spec/models/question_spec.rb b/spec/models/question_spec.rb
index b29054ea5..58332c854 100644
--- a/spec/models/question_spec.rb
+++ b/spec/models/question_spec.rb
@@ -10,7 +10,7 @@
   # test traits
 
   describe "with stuff" do
-    before :all do
+    before :each do
       @question = FactoryBot.build(:question, :with_stuff)
     end
     it "has a text" do
diff --git a/spec/models/quiz_certificate_spec.rb b/spec/models/quiz_certificate_spec.rb
index 9780e1d6d..631b6e871 100644
--- a/spec/models/quiz_certificate_spec.rb
+++ b/spec/models/quiz_certificate_spec.rb
@@ -1,12 +1,12 @@
 require "rails_helper"
 
 RSpec.describe(QuizCertificate, type: :model) do
+  # test validations - this is done on the level of the parent Medium model
+
   it "has a valid factory" do
     expect(FactoryBot.build(:quiz_certificate)).to be_valid
   end
 
-  # test validations - this is done one the level of the parent Medium model
-
   it "is invalid without a quiz" do
     expect(FactoryBot.build(:quiz_certificate, quiz: nil)).to be_invalid
   end
diff --git a/spec/models/quiz_graph_spec.rb b/spec/models/quiz_graph_spec.rb
index 8f1d970a1..c86c00deb 100644
--- a/spec/models/quiz_graph_spec.rb
+++ b/spec/models/quiz_graph_spec.rb
@@ -8,7 +8,7 @@
   # test traits and subfactories
 
   describe "linear graph" do
-    before :all do
+    before :each do
       @graph = FactoryBot.build(:quiz_graph, :linear)
     end
     it "does not contain errors" do
diff --git a/spec/models/quiz_spec.rb b/spec/models/quiz_spec.rb
index 1e35bc7dd..e0aa378f8 100644
--- a/spec/models/quiz_spec.rb
+++ b/spec/models/quiz_spec.rb
@@ -10,7 +10,7 @@
   # test traits and subfactories
 
   describe "with quiz graph" do
-    before :all do
+    before :each do
       @quiz = FactoryBot.build(:valid_quiz, :with_quiz_graph)
     end
     it "has no errors" do
diff --git a/spec/models/referral_spec.rb b/spec/models/referral_spec.rb
index 200521a9c..a1dcc4fa7 100644
--- a/spec/models/referral_spec.rb
+++ b/spec/models/referral_spec.rb
@@ -18,7 +18,7 @@
   # test traits and subfactories
 
   describe "with times" do
-    before :all do
+    before :each do
       @referral = FactoryBot.build(:referral, :with_times)
     end
     it "has a valid factory" do
diff --git a/spec/models/submission_cleaner_spec.rb b/spec/models/submission_cleaner_spec.rb
index a1670c666..b6ec9a260 100644
--- a/spec/models/submission_cleaner_spec.rb
+++ b/spec/models/submission_cleaner_spec.rb
@@ -7,7 +7,7 @@
   end
 
   describe "with sample submissions" do
-    before :all do
+    before :each do
       Term.destroy_all
       ActionMailer::Base.deliveries = []
       @term1 = FactoryBot.create(:term, year: Time.zone.today.year, season: "SS")
diff --git a/spec/models/talk_spec.rb b/spec/models/talk_spec.rb
index a18242241..d8750bd31 100644
--- a/spec/models/talk_spec.rb
+++ b/spec/models/talk_spec.rb
@@ -60,7 +60,7 @@
   end
 
   context "title methods" do
-    before :all do
+    before :each do
       I18n.with_locale(:de) do
         course = FactoryBot.build(:course, title: "Algebra 1",
                                            short_title: "Alg1")
@@ -132,7 +132,7 @@
   end
 
   context "locale methods" do
-    before :all do
+    before :each do
       I18n.with_locale(:de) do
         course = FactoryBot.build(:course, title: "Algebra 1",
                                            short_title: "Alg1")
@@ -159,7 +159,7 @@
   end
 
   context "position methods" do
-    before :all do
+    before :each do
       lecture = FactoryBot.build(:lecture)
       @talk1 = FactoryBot.create(:talk, lecture: lecture)
       @talk2 = FactoryBot.create(:talk, lecture: lecture)
diff --git a/spec/models/talk_tag_join_spec.rb b/spec/models/talk_tag_join_spec.rb
deleted file mode 100644
index 1b5e7edeb..000000000
--- a/spec/models/talk_tag_join_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require "rails_helper"
-
-RSpec.describe(TalkTagJoin, type: :model) do
-  pending "add some examples to (or delete) #{__FILE__}"
-end
diff --git a/spec/models/teachable_parser_spec.rb b/spec/models/teachable_parser_spec.rb
index 7068fb2ba..d021b5c17 100644
--- a/spec/models/teachable_parser_spec.rb
+++ b/spec/models/teachable_parser_spec.rb
@@ -4,7 +4,7 @@
   end
 
   describe "#teachables_as_strings" do
-    before :all do
+    before :each do
       DatabaseCleaner.clean
       course1 = FactoryBot.create(:course)
       lecture1 = FactoryBot.create(:lecture, course: course1)
diff --git a/spec/models/term_spec.rb b/spec/models/term_spec.rb
index 5806d9eb6..1eca3529b 100644
--- a/spec/models/term_spec.rb
+++ b/spec/models/term_spec.rb
@@ -40,7 +40,7 @@
   # test traits
 
   describe "summer term" do
-    before :all do
+    before :each do
       @term = FactoryBot.build(:term, :summer)
     end
     it "has a valid factory" do
diff --git a/spec/models/user_cleaner_spec.rb b/spec/models/user_cleaner_spec.rb
index 4549cfd4c..d33724a05 100644
--- a/spec/models/user_cleaner_spec.rb
+++ b/spec/models/user_cleaner_spec.rb
@@ -5,12 +5,15 @@
     expect(FactoryBot.build(:user_cleaner))
       .to be_kind_of(UserCleaner)
   end
-
-  it "can destroy users" do
-    n_users = User.all.size
-    u = FactoryBot.build(:user_cleaner, :with_hashed_user)
-    expect(User.all.size).to eq(n_users + 1)
-    u.delete_ghosts
-    expect(User.all.size).to eq(n_users)
-  end
+  # Right now, delete_ghosts is commented out in user_cleaner.rb
+  # as we want to avoid accidental deletion of users in production.
+  # We will come up with a new strategy for cleaning up old users.
+  #
+  # it "can destroy users" do
+  #   n_users = User.all.size
+  #   u = FactoryBot.build(:user_cleaner, :with_hashed_user)
+  #   expect(User.all.size).to eq(n_users + 1)
+  #   u.delete_ghosts
+  #   expect(User.all.size).to eq(n_users)
+  # end
 end
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index cc5dd6d5f..6675cbb53 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -34,7 +34,7 @@
   end
 
   describe "user with subscribed lectures" do
-    before :all do
+    before :each do
       @user = FactoryBot.build(:user, :with_lectures)
     end
     it "has a valid factory" do
@@ -70,7 +70,7 @@
   # test methods - NEEDS TO BE REFACTORED
 
   # describe '#related_lectures' do
-  #   before :all do
+  #   before :each do
   #     @preceding_course = FactoryBot.create(:course)
   #     @course = FactoryBot.create(:course)
   #     @lecture = FactoryBot.create(:lecture, course: @course)
diff --git a/spec/rails_helper.rb b/spec/rails_helper.rb
index 1c4c94a3f..202207bd1 100644
--- a/spec/rails_helper.rb
+++ b/spec/rails_helper.rb
@@ -34,10 +34,14 @@
 
   # For Devise >= 4.1.0
   config.include Devise::Test::ControllerHelpers, type: :controller
+
   # If you're not using ActiveRecord, or you'd prefer not to run each of your
   # examples within a transaction, remove the following line or assign false
   # instead of true.
+  # We set it to false here since we are using the DatabaseCleaner gem instead.
+  # Also see https://avdi.codes/configuring-database_cleaner-with-rails-rspec-capybara-and-selenium/
   config.use_transactional_fixtures = false
+
   # RSpec Rails can automatically mix in different behaviours to your tests
   # based on their file location, for example enabling you to call `get` and
   # `post` in specs under `spec/controllers`.
diff --git a/spec/requests/media_spec.rb b/spec/requests/media_spec.rb
index 5f9a62277..3aa2ec5fb 100644
--- a/spec/requests/media_spec.rb
+++ b/spec/requests/media_spec.rb
@@ -1,10 +1,20 @@
 require "rails_helper"
 
+NO_HITS_MSG = "The search has not returned any hits".freeze
+
+def expect_no_results(response)
+  expect(response.body).to include(NO_HITS_MSG)
+end
+
+def expect_all_results(response)
+  expect(response.body).not_to include(NO_HITS_MSG)
+  num_hits = parse_media_search(response)
+  expect(num_hits).to eq(Medium.where(released: "all").size)
+end
+
 RSpec.describe("Media", type: :request) do
   describe "#search_by" do
     before do
-      Medium.destroy_all
-
       @medium1 = FactoryBot.create(:medium, :with_teachable, :with_editors, :released,
                                    sort: "Nuesse", description: "Erstes Medium")
       @medium2 = FactoryBot.create(:medium, :with_teachable, :with_editors, :released,
@@ -16,6 +26,11 @@
       @medium5 = FactoryBot.create(:medium, :with_teachable, :with_editors, :released,
                                    :with_tags, sort: "Nuesse", description: "Anderes Medium")
 
+      @tag1 = FactoryBot.create(:tag, title: "mampf adventures")
+      @tag2 = FactoryBot.create(:tag, title: "topology")
+      @medium4.tags << @tag1
+      @medium5.tags << @tag2
+
       @lecture1 = FactoryBot.create(:lecture)
       @medium6 = FactoryBot.create(:medium, :with_teachable, :with_editors, :released,
                                    teachable: @lecture1, sort: "Nuesse",
@@ -27,7 +42,7 @@
       @medium8 = FactoryBot.create(:medium, :with_teachable, :with_editors,
                                    sort: "Nuesse", description: "Unveröffentlichtes Medium")
 
-      sign_in FactoryBot.create(:confirmed_user)
+      sign_in FactoryBot.create(:confirmed_user_en)
       User.last.subscribe_lecture!(@lecture1)
 
       Medium.reindex
@@ -50,17 +65,15 @@
     it "can search for all (released) media" do
       get media_search_path, params: @params
 
-      expect(response.body).not_to include("The search has not returned any hits")
       expect(response.body).not_to include("Unveröffentlichtes Medium")
-      hits = parse_media_search(response)
-      expect(hits).to eq(Medium.where(released: "all").size)
+      expect_all_results(response)
     end
 
     it "can search for media by title" do
       @params[:search][:fulltext] = "Erstes"
       get media_search_path, params: @params
 
-      expect(response.body).not_to include("The search has not returned any hits")
+      expect(response.body).not_to include(NO_HITS_MSG)
       expect(response.body).to include("Erstes Medium")
       hits = parse_media_search(response)
       expect(hits).to eq(2)
@@ -71,7 +84,7 @@
       @params[:search][:types] = ["Quiz"]
       get media_search_path, params: @params
 
-      expect(response.body).not_to include("The search has not returned any hits")
+      expect(response.body).not_to include(NO_HITS_MSG)
       expect(response.body).to include("Drittes Medium")
       hits = parse_media_search(response)
       expect(hits).to eq(1)
@@ -82,7 +95,7 @@
       @params[:search][:tag_ids] = @medium4.tags.pluck(:id)
       get media_search_path, params: @params
 
-      expect(response.body).not_to include("The search has not returned any hits")
+      expect(response.body).not_to include(NO_HITS_MSG)
       expect(response.body).to include("Getagtes Medium")
       hits = parse_media_search(response)
       expect(hits).to eq(1)
@@ -90,35 +103,40 @@
 
     it 'can do combined search with tagoperator "or" and description' do
       @params[:search][:all_tags] = 0
-      @params[:search][:tag_ids] = @medium4.tags.pluck(:id)
+      @params[:search][:tag_ids] = [@medium4.tags.pluck(:id), @medium5.tags.pluck(:id)].flatten
       @params[:search][:fulltext] = "Medium"
       get media_search_path, params: @params
 
-      expect(response.body).not_to include("The search has not returned any hits")
+      expect(response.body).not_to include(NO_HITS_MSG)
+      expect(response.body).to include("Getagtes Medium")
       hits = parse_media_search(response)
-      expect(hits).to eq(Medium.where(released: "all").size)
+      expect(hits).to eq(2)
     end
 
     it 'can do search with tagoperator "and" and description' do
       @params[:search][:tag_operator] = "and"
       @params[:search][:all_tags] = 0
-      @params[:search][:tag_ids] = @medium4.tags.pluck(:id)
+      @params[:search][:tag_ids] = [@tag1, @tag2].map(&:id)
       @params[:search][:fulltext] = "Medium"
       get media_search_path, params: @params
 
-      expect(response.body).not_to include("The search has not returned any hits")
-      expect(response.body).to include("Getagtes Medium")
-      hits = parse_media_search(response)
-      expect(hits).to eq(1)
+      expect_no_results(response)
     end
 
-    it 'can search for all media with tags by using tagoperator "and"' do
+    it '"all tags" has higher precedence than any tagoperator (here "and")' do
+      @params[:search][:all_tags] = 1
       @params[:search][:tag_operator] = "and"
       get media_search_path, params: @params
 
-      expect(response.body).not_to include("The search has not returned any hits")
-      hits = parse_media_search(response)
-      expect(hits).to eq(2)
+      expect_all_results(response)
+    end
+
+    it '"all tags" has higher precedence than any tagoperator (here "or")' do
+      @params[:search][:all_tags] = 1
+      @params[:search][:tag_operator] = "or"
+      get media_search_path, params: @params
+
+      expect_all_results(response)
     end
 
     it "can search by teacher" do
@@ -126,7 +144,7 @@
       @params[:search][:teacher_ids] = [@lecture1.teacher.id]
       get media_search_path, params: @params
 
-      expect(response.body).not_to include("The search has not returned any hits")
+      expect(response.body).not_to include(NO_HITS_MSG)
       hits = parse_media_search(response)
       expect(hits).to eq(2)
     end
@@ -135,7 +153,7 @@
       @params[:search][:lecture_option] = 1
       get media_search_path, params: @params
 
-      expect(response.body).not_to include("The search has not returned any hits")
+      expect(response.body).not_to include(NO_HITS_MSG)
       expect(response.body).to include("Erstes Medium mit Lehrer")
       hits = parse_media_search(response)
       expect(hits).to eq(1)
@@ -146,7 +164,7 @@
       @params[:search][:media_lectures] = [@lecture2.id]
       get media_search_path, params: @params
 
-      expect(response.body).not_to include("The search has not returned any hits")
+      expect(response.body).not_to include(NO_HITS_MSG)
       expect(response.body).to include("Zweites Medium mit Lehrer")
       hits = parse_media_search(response)
       expect(hits).to eq(1)
diff --git a/spec/rspec_inside_docker.py b/spec/rspec_inside_docker.py
new file mode 100644
index 000000000..b6d78a168
--- /dev/null
+++ b/spec/rspec_inside_docker.py
@@ -0,0 +1,61 @@
+import sys
+import subprocess
+
+# Path where the custom formatter of the Ruby Test explorer extension is memory-mapped
+FORMATTER_PATH_IN_DOCKER = "/root/tmp/formatter.rb"
+PROJECT_ROOT_FOLDER_NAME = "mampf"
+DOCKER_SERVICE_NAME = "mampf"
+
+
+def switch_formatter_path():
+    """
+    Memory-maps the custom formatter of the Ruby Test explorer extension.
+
+    The Ruby Test explorer extension uses a custom formatter to get a specific
+    output JSON format. The path to the formatter is automatically passed as an
+    argument to the rspec command by the extension. We need to replace this
+    path by the path to the memory-mapped formatter in the Docker container.
+    """
+
+    formatter_argument_index = None
+    for i, arg in enumerate(sys.argv):
+        if arg == '--require':
+            formatter_argument_index = i
+            break
+
+    if formatter_argument_index == None:
+        print('Please specify "--require path/to/custom/formatter.rb"')
+        sys.exit(1)
+
+    # Switch the path to the custom formatter to the memory-mapped path
+    formatter_path_on_host = sys.argv[formatter_argument_index + 1]
+    sys.argv[formatter_argument_index + 1] = FORMATTER_PATH_IN_DOCKER
+
+    return formatter_path_on_host
+
+
+def process_paths():
+    for i, arg in enumerate(sys.argv):
+        if not arg.startswith('./') and "spec" in arg:
+            sys.argv[i] = replace_absolute_paths_by_relative_paths(sys.argv[i])
+
+
+def replace_absolute_paths_by_relative_paths(path):
+    res = path.split(PROJECT_ROOT_FOLDER_NAME + '/')[1]
+    if not res:
+        print(f'Path {path}'
+              f' does not contain string "{PROJECT_ROOT_FOLDER_NAME}/"')
+        sys.exit(1)
+    return './' + res  # make path relative
+
+
+if __name__ == '__main__':
+    formatter_path_on_host = switch_formatter_path()
+    process_paths()
+
+    rspec_args = ' '.join(sys.argv[1:])
+    test_command = f'RAILS_ENV=test bundle exec rspec {rspec_args}'
+
+    docker_cmd = f'cd ./docker/test && docker compose run --rm -T --entrypoint="" -v {formatter_path_on_host}:{FORMATTER_PATH_IN_DOCKER} {DOCKER_SERVICE_NAME} sh -c "{test_command}"'
+
+    subprocess.call(docker_cmd, shell=True)
diff --git a/spec/support/database_cleaner.rb b/spec/support/database_cleaner.rb
index 36ccc0309..a8949daa8 100644
--- a/spec/support/database_cleaner.rb
+++ b/spec/support/database_cleaner.rb
@@ -1,17 +1,15 @@
+# See the docs here: https://www.rubydoc.info/github/DatabaseCleaner/database_cleaner
 RSpec.configure do |config|
   config.before(:suite) do
-    DatabaseCleaner.clean_with(:truncation, except: ["ar_internal_metadata"])
-  end
-
-  config.before(:each) do
     DatabaseCleaner.strategy = :transaction
+    DatabaseCleaner.clean_with(:truncation)
   end
 
   config.before(:each) do
     DatabaseCleaner.start
   end
 
-  config.after(:each) do
+  config.append_after(:each) do
     DatabaseCleaner.clean
   end
 end
diff --git a/spec/support/request_parse_helper.rb b/spec/support/request_parse_helper.rb
index 5a541afce..d19f8666d 100644
--- a/spec/support/request_parse_helper.rb
+++ b/spec/support/request_parse_helper.rb
@@ -2,12 +2,12 @@ module RequestParsingHelper
   # Parse the request body as HTML and return the number of hits
   def parse_media_search(response)
     search_results = response.body
-                             .match(/(?<=search_results.innerHTML = ').*(?=';)/)[0]
+                             .match(/(?<=searchResults.innerHTML = ').*(?=';)/)[0]
                              .gsub('\n', "")
     # strip whitespaces in search_results
     search_results = search_results.gsub(/\s+/, " ")
     # fix " in search_results
-    search_results = search_results.gsub('\\\"', '"')
+    search_results = search_results.gsub(/\\\"/, '"') # rubocop:disable Style/RedundantRegexpArgument,Style/RedundantRegexpEscape
     # fix \/ in search_results
     search_results = search_results.gsub('\\/', "/")
 
@@ -15,9 +15,9 @@ def parse_media_search(response)
     search_results = Nokogiri::HTML(search_results)
 
     # get text within first "col-12 col-lg-2" div
-    matches = search_results.css("div.col-12.col-lg-2").first.text
+    num_hits_text = search_results.css("div.col-12.col-lg-2").first.text
     # get number in matches
-    matches.match(/\d+/)[0].to_i
+    num_hits_text.match(/\d+/)[0].to_i
   end
 end