Unit Tests MUST NOT Access External Services (eg redis)

[hiddenalpha]

Expected behavior:
Unit tests do NOT require external services. If they do, they are integration tests and can be run when explicitly told to do so.

Actual behavior:
There are some unit test which require external services (redis in this case). So they are an integration test by definition...

Error Message (filtered):

[INFO] Running org.swisspush.gateleen.core.lock.lua.ReleaseLockLuaScriptTests
[ERROR] Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.021 s <<< FAILURE! - in org.swisspush.gateleen.core.lock.lua.ReleaseLockLuaScriptTests
[ERROR] org.swisspush.gateleen.core.lock.lua.ReleaseLockLuaScriptTests  Time elapsed: 0.007 s  <<< ERROR!
redis.clients.jedis.exceptions.JedisConnectionException: Failed to create socket.
Caused by: java.net.ConnectException: Connection refused
...
[ERROR] Errors: 
[ERROR]   ReleaseLockLuaScriptTests>AbstractLuaScriptTest.checkRedisAvailable:24 » JedisConnection
...
[INFO] gateleen ........................................... SUCCESS [  0.481 s]
[INFO] gateleen-testhelper ................................ SUCCESS [  2.125 s]
[INFO] gateleen-core ...................................... FAILURE [ 12.595 s]
...
[INFO] BUILD FAILURE
...
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:3.0.0-M5:test (default-test) on project gateleen-core: There are test failures.
...

Reproducer:

#!/bin/sh
set -e \
  && SUDO=sudo \
  && gateleenGitTag="v2.1.27" \
  && workDir="/home/user/work" \
  && cacheDir="/var/tmp" \
  \
  && $SUDO apt update \
  && $SUDO apt install --no-install-recommends -y \
         curl maven openjdk-21-jdk-headless \
  \
  && curl -SL https://github.com/swisspush/gateleen/archive/refs/tags/"${gateleenGitTag:?}".tar.gz > "${cacheDir:?}/gateleen-${gateleenGitTag:?}.tgz" \
  && mkdir -p "${workDir:?}/gateleen" \
  && cd       "${workDir:?}/gateleen" \
  && tar --strip-components 1 -xf "${cacheDir:?}/gateleen-${gateleenGitTag:?}.tgz" \
  && mvn clean \
  && mvn verify -PpublicRepos \

Why I consider this to be a bug:
It is crazy annoying, everytime one builds gateleen locally, it either: Does not work due to not running redis, or even worse: It enbloatens the local redis with unwanted test data. At times, it also triggers weird side-effects as other redis clients now may see their state corrupted.
Or for short: Stuff that requires ugly workarounds, is a bug.