diff --git a/.github/workflows/scripts/test_utils.sh b/.github/workflows/scripts/test_utils.sh
new file mode 100644
index 00000000..66d47460
--- /dev/null
+++ b/.github/workflows/scripts/test_utils.sh
@@ -0,0 +1,47 @@
+#!/bin/bash
+check_env_var() {
+  # Expected usage: check_env_var "MY_ENV_VAR" "foo"
+  var_name="$1"
+  expected="$2"
+  actual="${!var_name}"
+  if [ "$actual" != "$expected" ]; then
+    echo "ERROR: $var_name is '$actual', expected '$expected'" >&2
+    exit 1
+  else
+    echo "$var_name is correctly set to '$expected'"
+  fi
+}
+
+check_disallowed_env_prefix() {
+  prefix="$1"
+  shift
+  whitelist=("$@")
+
+  disallowed=()
+
+  while IFS='=' read -r var _; do
+    if [[ "$var" == "$prefix"* ]]; then
+      allowed=false
+      for allowed_var in "${whitelist[@]}"; do
+        if [[ "$var" == "$allowed_var" ]]; then
+          allowed=true
+          break
+        fi
+      done
+
+      if ! $allowed; then
+        disallowed+=("$var")
+      fi
+    fi
+  done < <(env)
+
+  if [ "${#disallowed[@]}" -ne 0 ]; then
+    echo "ERROR: Found disallowed environment variables with prefix '$prefix':" >&2
+    for var in "${disallowed[@]}"; do
+      echo "  - $var" >&2
+    done
+    exit 1
+  else
+    echo "✅ No disallowed environment variables with prefix '$prefix' found."
+  fi
+}
diff --git a/.github/workflows/tests_eessi_extend_module.yml b/.github/workflows/tests_eessi_extend_module.yml
new file mode 100644
index 00000000..ef66bcf0
--- /dev/null
+++ b/.github/workflows/tests_eessi_extend_module.yml
@@ -0,0 +1,127 @@
+# documentation: https://help.github.com/en/articles/workflow-syntax-for-github-actions
+name: Tests for EESSI-extend module functionality in software.eessi.io
+on:
+  push:
+    branches: [ "*-software.eessi.io" ]
+  pull_request:
+permissions:
+  contents: read # to fetch code (actions/checkout)
+jobs:
+  basic_checks:
+    runs-on: ubuntu-22.04
+    strategy:
+      fail-fast: false
+      matrix:
+        EESSI_VERSION:
+          - '2023.06'
+    steps:
+      - name: Check out software-layer repository
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+          
+      - name: Mount EESSI CernVM-FS repository
+        uses: eessi/github-action-eessi@v3
+        with:
+          eessi_stack_version: ${{matrix.EESSI_VERSION}}
+          use_eessi_module: true
+
+      - name: Install the EESSI-extend shipped with the repository
+        run: |
+          # Define a function to check the values of environment variables
+          # and another that checks an environment does not contain environment 
+          # variables matching a certain pattern
+          source .github/workflows/scripts/test_utils.sh
+
+          # Let's start from a clean slate (unload the EESSI module)
+          module purge
+          check_disallowed_env_prefix EESSI_
+          check_disallowed_env_prefix EASYBUILD_
+
+          # Load the EESSI module
+          module load EESSI/${{matrix.EESSI_VERSION}}
+          check_disallowed_env_prefix EASYBUILD_
+
+          # Load EasyBuild to install EESSI-extend
+          module load EasyBuild
+          # Set an installation path
+          export MY_INSTALLATION_PATH=/tmp/easybuild
+          export EASYBUILD_PREFIX=$MY_INSTALLATION_PATH
+          eb EESSI-extend-easybuild.eb --rebuild
+
+          # Verify that we can pick the installed version up
+          module use $MY_INSTALLATION_PATH/modules/all
+          module load EESSI-extend/${{matrix.EESSI_VERSION}}-easybuild
+          echo $EBROOTEESSIMINEXTEND | grep $MY_INSTALLATION_PATH || { echo "ERROR: Installed version of EESSI-extend not picked up (loaded $EBROOTEESSIMINEXTEND)" >&2; exit 1; }
+          module unload EESSI-extend
+          # That should have unset all EasyBuild envvars (including EASYBUILD_PREFIX)
+          check_disallowed_env_prefix EASYBUILD_
+          module unuse $MY_INSTALLATION_PATH/modules/all
+
+      - name: Run tests for EESSI-extend in the various CPU-only scenarios
+        run: |
+          export MY_INSTALLATION_PATH=/tmp/easybuild
+
+          # Define a function to check the values of environment variables
+          # and another that checks an environment does not contain environment 
+          # variables matching a certain pattern
+          source .github/workflows/scripts/test_utils.sh
+
+          # Let's start from a clean slate
+          module purge
+          module load EESSI/${{matrix.EESSI_VERSION}}
+          # Access the installed EESSI-extend
+          module use "$MY_INSTALLATION_PATH"/modules/all
+          check_disallowed_env_prefix EASYBUILD_
+
+          # Configure for CVMFS install
+          export EESSI_CVMFS_INSTALL=1
+          module load EESSI-extend/${{matrix.EESSI_VERSION}}-easybuild
+          # check some common EasyBuild settings
+          check_env_var "EASYBUILD_READ_ONLY_INSTALLDIR" "1"
+          check_env_var "EASYBUILD_ALLOW_LOADED_MODULES" "EasyBuild,EESSI-extend"
+          check_env_var "EASYBUILD_SYSROOT" "$EESSI_EPREFIX"
+          check_env_var "EASYBUILD_HOOKS" "/cvmfs/software.eessi.io/versions/${{matrix.EESSI_VERSION}}/init/easybuild/eb_hooks.py"
+          check_env_var "EASYBUILD_RPATH" "1"
+          check_env_var "EASYBUILD_FILTER_ENV_VARS" "LD_LIBRARY_PATH"
+          # check some specific ones
+          check_env_var "EASYBUILD_INSTALLPATH" "$EESSI_SOFTWARE_PATH"
+          check_env_var "EASYBUILD_UMASK" "022"
+          # unload and check the environment is clean again
+          module unload EESSI-extend
+          check_disallowed_env_prefix EASYBUILD_
+          unset EESSI_CVMFS_INSTALL
+
+          # Now configure for a site
+          export EESSI_SITE_INSTALL=1
+          module load EESSI-extend/${{matrix.EESSI_VERSION}}-easybuild
+          # check some specific envvars
+          check_env_var "EASYBUILD_INSTALLPATH" "$EESSI_SITE_SOFTWARE_PATH"
+          check_env_var "EASYBUILD_UMASK" "022"
+          # unload and check the environment is clean again
+          module unload EESSI-extend
+          check_disallowed_env_prefix EASYBUILD_
+          unset EESSI_SITE_INSTALL
+
+          # Now for a project
+          export EESSI_PROJECT_INSTALL="$MY_INSTALLATION_PATH"
+          module load EESSI-extend/${{matrix.EESSI_VERSION}}-easybuild
+          # check some specific envvars
+          check_env_var "EASYBUILD_INSTALLPATH" "$MY_INSTALLATION_PATH/versions/$EESSI_VERSION/software/linux/$EESSI_SOFTWARE_SUBDIR"
+          check_env_var "EASYBUILD_UMASK" "002"
+          check_env_var "EASYBUILD_GROUP_WRITABLE_INSTALLDIR" "1"
+          # unload and check the environment is clean again
+          module unload EESSI-extend
+          check_disallowed_env_prefix EASYBUILD_
+          unset EESSI_PROJECT_INSTALL
+
+          # Now for a user
+          export EESSI_USER_INSTALL="$MY_INSTALLATION_PATH/$USER"
+          mkdir -p $EESSI_USER_INSTALL  # must exist
+          module load EESSI-extend/${{matrix.EESSI_VERSION}}-easybuild
+          # check some specific envvars
+          check_env_var "EASYBUILD_INSTALLPATH" "$MY_INSTALLATION_PATH/$USER/versions/$EESSI_VERSION/software/linux/$EESSI_SOFTWARE_SUBDIR"
+          check_env_var "EASYBUILD_UMASK" "077"
+          # unload and check the environment is clean again
+          module unload EESSI-extend
+          check_disallowed_env_prefix EASYBUILD_
+          unset EESSI_USER_INSTALL
+