Add tests

.gitlab-ci.yml

+image: node:18.15.0
+
+stages:
+  - test
+
+# === Caches ===
+.yarn-cache: &yarn-cache
+  key: yarn-$CI_JOB_IMAGE
+  paths:
+    - .yarn
+
+# === Proxy ===
+# Description: sets up the proxy needed for the runner inside of the PTB. Produces a build.env that is used in the next jobs
+proxy:
+  stage: .pre
+  script:
+    - touch build.env
+    - if [[ "$CI_RUNNER_TAGS" == *"behind_proxy"* ]]; then
+    -   echo "behind_proxy=true" >> build.env
+    -   echo "http_proxy=http://webproxy.bs.ptb.de:8080/" >> build.env
+    -   echo "https_proxy=http://webproxy.bs.ptb.de:8080/" >> build.env
+    - fi
+  artifacts:
+    reports:
+      dotenv: build.env
+
+
+# === Yarn Install ===
+# Description: installs and caches dependencies
+.yarn-install: &yarn-install
+  - corepack enable
+  # proxy settings
+  - if [[ "$behind_proxy" == true ]]; then
+  -   npm config set proxy $http_proxy
+  -   npm config set https-proxy $https_proxy
+  -   yarn config set -H httpProxy $http_proxy
+  -   yarn config set -H httpsProxy $https_proxy
+  - fi
+  # install deps
+  - yarn install --immutable
+
+# === Job: Unit Tests ===
+# Description: this job runs the unit tests
+test:
+  stage: test
+  needs: ["proxy"]
+  script:
+    - *yarn-install
+    - yarn run test:unit --ci
+  cache:
+    - <<: *yarn-cache
+  artifacts:
+    when: always
+    reports:
+      junit:
+        - junit.xml