diff --git a/action.yml b/action.yml
index 6ed5acc..09f91ef 100644
--- a/action.yml
+++ b/action.yml
@@ -51,32 +51,19 @@ runs:
       env:
         REDMINE_DIR: ${{ inputs.path }}
 
-    - name: Install dependencies
+    - name: Set up base environment
       run: |
-        sudo apt-get update; \
-        sudo apt-get install -y --no-install-recommends \
-          build-essential \
-          bzr git mercurial subversion cvs \
-          ghostscript \
-          gsfonts \
-          imagemagick libmagick++-dev \
-          libnss3-dev;
-      shell: bash
-
-    - name: Allow ImageMagick to read PDF files
-      run: |
-        sudo sed -ri 's/(rights)="none" (pattern="PDF")/\1="read" \2/' /etc/ImageMagick-6/policy.xml
-      shell: bash
-
-    - name: Set up Google Chrome for system tests
-      run: |
-        wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
-        echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" | sudo tee /etc/apt/sources.list.d/google-chrome.list
-        sudo apt-get update
-        sudo apt-get install -y --no-install-recommends google-chrome-stable
+        # For example: v5.1.3.stable -> "setup-base-5.1.sh"
+        setup_base_script="setup-base-$REDMINE_VERSION_MAJOR.$REDMINE_VERSION_MINOR.sh"
 
-        echo GOOGLE_CHROME_OPTS_ARGS="headless,disable-gpu,no-sandbox,disable-dev-shm-usage" >> $GITHUB_ENV
+        if [ -e ./scripts/$setup_base_script ]; then
+          ./scripts/$setup_base_script
+        else
+          ./scripts/setup-base-next.sh
+        fi
       shell: bash
+      env:
+        REDMINE_DIR: ${{ inputs.path }}
 
     - name: Set up PostgreSQL database
       if: ${{ startsWith(inputs.database, 'postgres:') }}
@@ -101,13 +88,6 @@ runs:
       env:
         REDMINE_DIR: ${{ inputs.path }}
 
-      # https://www.redmine.org/issues/40802
-    - name: Fix LoadError in Redmine 4.2
-      if: ${{ env.REDMINE_VERSION_MAJOR < 5 }}
-      run: echo "gem 'builder', '~> 3.2.4'" >> Gemfile.local
-      shell: bash
-      working-directory: ${{ inputs.path }}
-
     - name: Set up Ruby and install dependencies
       uses: ruby/setup-ruby@v1
       with:
diff --git a/scripts/setup-base-4.2.sh b/scripts/setup-base-4.2.sh
new file mode 100644
index 0000000..1af3bc7
--- /dev/null
+++ b/scripts/setup-base-4.2.sh
@@ -0,0 +1,27 @@
+#!/bin/bash
+
+set -eu
+
+# Install dependencies
+sudo apt-get update; \
+sudo apt-get install -y --no-install-recommends \
+  build-essential \
+  bzr git mercurial subversion cvs \
+  ghostscript \
+  gsfonts \
+  imagemagick libmagick++-dev \
+  libnss3-dev;
+
+# Allow ImageMagick to read PDF files
+sudo sed -ri 's/(rights)="none" (pattern="PDF")/\1="read" \2/' /etc/ImageMagick-6/policy.xml
+
+# Set up Google Chrome for system tests
+wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
+echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" | sudo tee /etc/apt/sources.list.d/google-chrome.list
+sudo apt-get update
+sudo apt-get install -y --no-install-recommends google-chrome-stable
+echo GOOGLE_CHROME_OPTS_ARGS="headless,disable-gpu,no-sandbox,disable-dev-shm-usage" >> $GITHUB_ENV
+
+# Fix LoadError cannot load such file -- builder
+# https://www.redmine.org/issues/40802
+echo "gem 'builder', '~> 3.2.4'" >> $REDMINE_DIR/Gemfile.local
diff --git a/scripts/setup-base-5.0.sh b/scripts/setup-base-5.0.sh
new file mode 100644
index 0000000..f7add9b
--- /dev/null
+++ b/scripts/setup-base-5.0.sh
@@ -0,0 +1,23 @@
+#!/bin/bash
+
+set -eu
+
+# Install dependencies
+sudo apt-get update; \
+sudo apt-get install -y --no-install-recommends \
+  build-essential \
+  bzr git mercurial subversion cvs \
+  ghostscript \
+  gsfonts \
+  imagemagick libmagick++-dev \
+  libnss3-dev;
+
+# Allow ImageMagick to read PDF files
+sudo sed -ri 's/(rights)="none" (pattern="PDF")/\1="read" \2/' /etc/ImageMagick-6/policy.xml
+
+# Set up Google Chrome for system tests
+wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
+echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" | sudo tee /etc/apt/sources.list.d/google-chrome.list
+sudo apt-get update
+sudo apt-get install -y --no-install-recommends google-chrome-stable
+echo GOOGLE_CHROME_OPTS_ARGS="headless,disable-gpu,no-sandbox,disable-dev-shm-usage" >> $GITHUB_ENV
diff --git a/scripts/setup-base-5.1.sh b/scripts/setup-base-5.1.sh
new file mode 100644
index 0000000..f7add9b
--- /dev/null
+++ b/scripts/setup-base-5.1.sh
@@ -0,0 +1,23 @@
+#!/bin/bash
+
+set -eu
+
+# Install dependencies
+sudo apt-get update; \
+sudo apt-get install -y --no-install-recommends \
+  build-essential \
+  bzr git mercurial subversion cvs \
+  ghostscript \
+  gsfonts \
+  imagemagick libmagick++-dev \
+  libnss3-dev;
+
+# Allow ImageMagick to read PDF files
+sudo sed -ri 's/(rights)="none" (pattern="PDF")/\1="read" \2/' /etc/ImageMagick-6/policy.xml
+
+# Set up Google Chrome for system tests
+wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
+echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" | sudo tee /etc/apt/sources.list.d/google-chrome.list
+sudo apt-get update
+sudo apt-get install -y --no-install-recommends google-chrome-stable
+echo GOOGLE_CHROME_OPTS_ARGS="headless,disable-gpu,no-sandbox,disable-dev-shm-usage" >> $GITHUB_ENV
diff --git a/scripts/setup-base-next.sh b/scripts/setup-base-next.sh
new file mode 100644
index 0000000..f7add9b
--- /dev/null
+++ b/scripts/setup-base-next.sh
@@ -0,0 +1,23 @@
+#!/bin/bash
+
+set -eu
+
+# Install dependencies
+sudo apt-get update; \
+sudo apt-get install -y --no-install-recommends \
+  build-essential \
+  bzr git mercurial subversion cvs \
+  ghostscript \
+  gsfonts \
+  imagemagick libmagick++-dev \
+  libnss3-dev;
+
+# Allow ImageMagick to read PDF files
+sudo sed -ri 's/(rights)="none" (pattern="PDF")/\1="read" \2/' /etc/ImageMagick-6/policy.xml
+
+# Set up Google Chrome for system tests
+wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
+echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" | sudo tee /etc/apt/sources.list.d/google-chrome.list
+sudo apt-get update
+sudo apt-get install -y --no-install-recommends google-chrome-stable
+echo GOOGLE_CHROME_OPTS_ARGS="headless,disable-gpu,no-sandbox,disable-dev-shm-usage" >> $GITHUB_ENV