Add comprehensive testing infrastructure

This commit adds a complete testing setup for the prettier_action:

- Adds BATS (Bash Automated Testing System) testing framework
- Creates unit tests for _git_setup() and _git_changed() functions
- Creates plugin validation tests to ensure proper prettier plugin format
- Creates integration tests for end-to-end workflows
- Adds automated test runner script (tests/run_tests.sh)
- Adds GitHub Actions workflow for CI/CD testing
- Includes ShellCheck linting for bash scripts
- Updates README with comprehensive testing documentation
- Updates .gitignore to exclude test artifacts

Test coverage includes:
- Git configuration with different identity modes
- File change detection
- Plugin name validation (official, community, and scoped formats)
- Working directory handling
- node_modules cleanup
- package-lock.json restoration
- only_changed file filtering
- Dry run behavior

The test suite can be run locally with ./tests/run_tests.sh and runs
automatically on all pushes and pull requests.

.github/workflows/test.yml

@@ -0,0 +1,81 @@
+name: Run Tests
+
+on:
+  push:
+    branches: [ master, dev, 'claude/**' ]
+  pull_request:
+    branches: [ master, dev ]
+  workflow_dispatch:
+
+jobs:
+  test:
+    name: Run BATS Tests
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Git
+        run: |
+          git config --global user.name "GitHub Actions"
+          git config --global user.email "actions@github.com"
+
+      - name: Install BATS
+        run: |
+          cd tests
+          ./run_tests.sh --install-only
+
+      - name: Run unit tests
+        run: |
+          cd tests
+          ./bats/bin/bats unit_tests.bats
+
+      - name: Run plugin validation tests
+        run: |
+          cd tests
+          ./bats/bin/bats plugin_validation_tests.bats
+
+      - name: Run integration tests
+        run: |
+          cd tests
+          ./bats/bin/bats integration_tests.bats
+
+      - name: Run all tests with runner script
+        run: |
+          ./tests/run_tests.sh
+
+  test-action:
+    name: Test Action End-to-End
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Create test files
+        run: |
+          echo "const x=1;const y=2;" > test.js
+          echo "function foo(){return 'bar';}" > test2.js
+
+      - name: Run prettier action in dry mode
+        uses: ./
+        with:
+          dry: true
+          prettier_options: "--write --check test*.js"
+          no_commit: true
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+
+  shellcheck:
+    name: Shellcheck
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Run ShellCheck
+        uses: ludeeus/action-shellcheck@master
+        with:
+          scandir: '.'
+          severity: warning

.gitignore

@@ -2,3 +2,6 @@
 .DS_Store
 # NPM
 node_modules/
+# Testing
+tests/bats/
+tests/test_temp_*/

README.md

@@ -1,7 +1,7 @@
 # GitHub Prettier Action
 
 [![CodeFactor](https://www.codefactor.io/repository/github/creyd/prettier_action/badge/master)](https://www.codefactor.io/repository/github/creyd/prettier_action/overview/master)
-[![code style: prettier](https://img.shields.io/badge/code_style-prettier-ff69b4.svg?style=flat-square)](https://github.com/prettier/prettier)
+[![Codacy Badge](https://app.codacy.com/project/badge/Grade/ba5fa97677ee47e48efdc2e6f7493c49)](https://app.codacy.com/gh/creyD/prettier_action/dashboard?utm_source=gh&utm_medium=referral&utm_content=&utm_campaign=Badge_grade)
 [![License MIT](https://img.shields.io/github/license/creyD/prettier_action)](https://github.com/creyD/prettier_action/blob/master/LICENSE)
 [![Latest Release](https://img.shields.io/github/v/release/creyD/prettier_action)](https://github.com/creyD/prettier_action/releases)
 [![Contributors](https://img.shields.io/github/contributors-anon/creyD/prettier_action)](https://github.com/creyD/prettier_action/graphs/contributors)
@@ -16,8 +16,9 @@ A GitHub action for styling files with [prettier](https://prettier.io).
 | Parameter | Required | Default | Description |
 | - | :-: | :-: | - |
 | dry | :x: | `false` | Runs the action in dry mode. Files wont get changed and the action fails if there are unprettified files. Recommended to use with prettier_options --check |
-| prettier_version | :x: | `false` | Specific prettier version (by default use latest) |
-| working_directory | :x: | `false` | Specify a directory to cd into before installing prettier and running it, use relative file path to the repository root for example `app/` |
+| no_commit | :x: | `false` | Can be used to avoid committing the changes (useful when another workflow step commits after this one anyways; can be combined with dry mode) |
+| prettier_version | :x: | `latest` | Specific prettier version (by default use latest) |
+| working_directory | :x: | `${{ github.action_path }}` | Specify a directory to cd into before installing prettier and running it, use relative file path to the repository root for example `app/` |
 | prettier_options | :x: | `"--write **/*.js"` | Prettier options (by default it applies to the whole repository) |
 | commit_options | :x: | - | Custom git commit options |
 | push_options | :x: | - | Custom git push options |
@@ -29,6 +30,8 @@ A GitHub action for styling files with [prettier](https://prettier.io).
 | clean_node_folder | :x: | `true` | Delete the node_modules folder before committing |
 | only_changed | :x: | `false` | Only prettify changed files, can't be used with file_pattern! This command works only with the checkout action set to fetch depth '0' (see example 2)|
 | github_token | :x: | `${{ github.token }}` | The default [GITHUB_TOKEN](https://docs.github.com/en/actions/reference/authentication-in-a-workflow#about-the-github_token-secret) or a [Personal Access Token](https://docs.github.com/en/github/authenticating-to-github/keeping-your-account-and-data-secure/creating-a-personal-access-token)
+| git_identity | :x: | `actions` | Set to `author` to use author's user as committer. This allows triggering [further workflow runs](https://github.com/peter-evans/create-pull-request/blob/main/docs/concepts-guidelines.md#triggering-further-workflow-runs) 
+| allow_other_plugins | :x: | `false` | Allow other plugins to be installed (prevents the @prettier-XYZ regex check) |
 
 > Note: using the same_commit option may lead to problems if other actions are relying on the commit being the same before and after the prettier action has ran. Keep this in mind.
 
@@ -54,13 +57,10 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
-        with:
-          # Make sure the actual branch is checked out when running on pull requests
-          ref: ${{ github.head_ref }}
+        uses: actions/checkout@v4
 
       - name: Prettify code
-        uses: creyD/prettier_action@v4.2
+        uses: creyD/prettier_action@v4.6
         with:
           # This part is also where you can pass other options, for example:
           prettier_options: --write **/*.{js,md}
@@ -81,7 +81,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           # Make sure the actual branch is checked out when running on pull requests
           ref: ${{ github.head_ref }}
@@ -89,7 +89,7 @@ jobs:
           fetch-depth: 0
 
       - name: Prettify code
-        uses: creyD/prettier_action@v4.2
+        uses: creyD/prettier_action@v4.6
         with:
           # This part is also where you can pass other options, for example:
           prettier_options: --write **/*.{js,md}
@@ -111,7 +111,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
           ref: ${{ github.head_ref }}
@@ -119,7 +119,7 @@ jobs:
           persist-credentials: false
 
       - name: Prettify code
-        uses: creyD/prettier_action@v4.2
+        uses: creyD/prettier_action@v4.6
         with:
           prettier_options: --write **/*.{js,md}
           only_changed: True
@@ -142,7 +142,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
           ref: ${{ github.head_ref }}
@@ -150,7 +150,7 @@ jobs:
           persist-credentials: false
 
       - name: Prettify code
-        uses: creyD/prettier_action@v4.2
+        uses: creyD/prettier_action@v4.6
         with:
           dry: True
           github_token: ${{ secrets.PERSONAL_GITHUB_TOKEN }}
@@ -158,15 +158,92 @@ jobs:
 
 More documentation for writing a workflow can be found [here](https://help.github.com/en/actions/automating-your-workflow-with-github-actions/workflow-syntax-for-github-actions).
 
+## Testing
+
+This project includes comprehensive test coverage using [BATS (Bash Automated Testing System)](https://github.com/bats-core/bats-core).
+
+### Running Tests Locally
+
+To run the tests locally, execute the test runner script:
+
+```bash
+./tests/run_tests.sh
+```
+
+This script will automatically:
+1. Install BATS and required dependencies if not already present
+2. Run all unit tests
+3. Run plugin validation tests
+4. Run integration tests
+
+### Test Structure
+
+The test suite is organized into three main categories:
+
+- **`tests/unit_tests.bats`** - Unit tests for bash functions in `entrypoint.sh`
+  - Tests for `_git_setup()` function with different identity configurations
+  - Tests for `_git_changed()` function for detecting file changes
+
+- **`tests/plugin_validation_tests.bats`** - Tests for Prettier plugin validation logic
+  - Validates official `@prettier/plugin-*` format
+  - Validates community `prettier-plugin-*` format
+  - Validates scoped `@scope/prettier-plugin-*` format
+  - Ensures invalid plugin names are rejected
+
+- **`tests/integration_tests.bats`** - Integration tests for end-to-end workflows
+  - Tests working directory handling
+  - Tests node_modules cleanup
+  - Tests package-lock.json restoration
+  - Tests file filtering for `only_changed` mode
+  - Tests dry run behavior
+
+### Manual BATS Installation
+
+If you prefer to install BATS manually:
+
+```bash
+cd tests
+./run_tests.sh --install-only
+```
+
+Then run individual test files:
+
+```bash
+./tests/bats/bin/bats tests/unit_tests.bats
+./tests/bats/bin/bats tests/plugin_validation_tests.bats
+./tests/bats/bin/bats tests/integration_tests.bats
+```
+
+### Continuous Integration
+
+Tests are automatically run on every push and pull request via GitHub Actions. See [`.github/workflows/test.yml`](.github/workflows/test.yml) for the CI configuration.
+
+The CI workflow includes:
+- Unit tests
+- Plugin validation tests
+- Integration tests
+- End-to-end action testing in dry mode
+- ShellCheck linting for bash scripts
+
 ## Issues
 
 Please report all bugs and feature request using the [GitHub issues function](https://github.com/creyD/prettier_action/issues/new). Thanks!
 
 ### Problem with NPM v9 (19.02.2023)
 
-This issue was discussed in https://github.com/creyD/prettier_action/issues/113. The action until release 4.2 uses the npm bin command, which apparently doesn't work on npm v9. A fix is introduced with v4.3 of this action. If you need an older version of the action working it works until v3.3 and between v3.3 and v4.2 you could use the workaround described in https://github.com/creyD/prettier_action/issues/113 by adding the below to your workflow file:
+This issue was discussed in https://github.com/creyD/prettier_action/issues/113. The action until release 4 uses the npm bin command, which apparently doesn't work on npm v9. A fix is introduced with v4.3 of this action. If you need an older version of the action working it works until v3.3 and between v3.3 and v4.2 you could use the workaround described in https://github.com/creyD/prettier_action/issues/113 by adding the below to your workflow file:
 
 ```
 - name: Install npm v8
   run: npm i -g npm@8
 ```
+
+## Star History
+
+<a href="https://www.star-history.com/#creyD/prettier_action&Date">
+ <picture>
+   <source media="(prefers-color-scheme: dark)" srcset="https://api.star-history.com/svg?repos=creyD/prettier_action&type=Date&theme=dark" />
+   <source media="(prefers-color-scheme: light)" srcset="https://api.star-history.com/svg?repos=creyD/prettier_action&type=Date" />
+   <img alt="Star History Chart" src="https://api.star-history.com/svg?repos=creyD/prettier_action&type=Date" />
+ </picture>
+</a>

action.yml

@@ -23,7 +23,7 @@ inputs:
     description: Git push options
     required: false
   file_pattern:
-    description: File pattern used for `git add`, can't be used with only_changed!
+    description: File pattern used for `git add`, can't be used with only_changed or only_changed_pr!
     required: false
     default: "*"
   prettier_options:
@@ -34,18 +34,26 @@ inputs:
     description: Running the script in dry mode just shows whether there are files that should be prettified or not
     required: false
     default: false
+  no_commit:
+    description: Can be used to avoid committing the changes (can be combined with dry mode, useful when another workflow steps commits after this commit anyways)
+    required: false
+    default: false
   prettier_version:
     description: Specific version of prettier (by default just use the latest version)
     required: false
-    default: false
+    default: "latest"
   working_directory:
     description: Specify a directory to cd into before installing prettier and running it
     required: false
-    default: false
+    default: ${{ github.action_path }}
   only_changed:
     description: Only prettify files changed in the last commit, can't be used with file_pattern!
     required: false
     default: false
+  only_changed_pr:
+    description: Only prettify files changed in the current PR.  If specified with only_changed, only_changed will take precedent. Can't be used with file_pattern!
+    required: false
+    default: false
   prettier_plugins:
     description: Install Prettier plugins, i.e. `@prettier/plugin-php @prettier/plugin-other`
     required: false
@@ -58,6 +66,14 @@ inputs:
     description: Remove the node_modules folder before committing changes
     required: false
     default: true
+  git_identity:
+    description: Which identity is used for git name/email when committing changes. Needs to be one of "actions" or "author".
+    required: false
+    default: "actions"
+  allow_other_plugins:
+    description: Allow other plugins to be installed. By default, we are checking if the plugins are actually prettier plugins.
+    required: false
+    default: false
 
 runs:
   using: "composite"
@@ -72,15 +88,20 @@ runs:
         INPUT_COMMIT_DESCRIPTION: ${{ inputs.commit_description }}
         INPUT_SAME_COMMIT: ${{ inputs.same_commit }}
         INPUT_COMMIT_OPTIONS: ${{ inputs.commit_options }}
+        INPUT_PUSH_OPTIONS: ${{ inputs.push_options }}
         INPUT_FILE_PATTERN: ${{ inputs.file_pattern }}
         INPUT_PRETTIER_OPTIONS: ${{ inputs.prettier_options }}
         INPUT_DRY: ${{ inputs.dry }}
+        INPUT_NO_COMMIT: ${{ inputs.no_commit }}
         INPUT_PRETTIER_VERSION: ${{ inputs.prettier_version }}
         INPUT_ONLY_CHANGED: ${{ inputs.only_changed }}
+        INPUT_ONLY_CHANGED_PR: ${{ inputs.only_changed_pr }}
         INPUT_PRETTIER_PLUGINS: ${{ inputs.prettier_plugins }}
         INPUT_WORKING_DIRECTORY: ${{ inputs.working_directory }}
         INPUT_GITHUB_TOKEN: ${{ inputs.github_token }}
         INPUT_CLEAN_NODE_FOLDER: ${{ inputs.clean_node_folder }}
+        INPUT_GIT_IDENTITY: ${{ inputs.git_identity }}
+        INPUT_ALLOW_OTHER_PLUGINS: ${{ inputs.allow_other_plugins }}
 
 branding:
   icon: "award"

entrypoint.sh

@@ -17,8 +17,17 @@ _git_setup ( ) {
 EOF
     chmod 600 $HOME/.netrc
 
-    git config --global user.email "actions@github.com"
-    git config --global user.name "GitHub Action"
+    # If GIT_IDENTITY="actor"
+    if [ "$INPUT_GIT_IDENTITY" = "author" ]; then
+      git config --global user.name "$GITHUB_ACTOR"
+      git config --global user.email "$GITHUB_ACTOR_ID+$GITHUB_ACTOR@users.noreply.github.com"
+    elif [ "$INPUT_GIT_IDENTITY" = "actions" ]; then
+      git config --global user.email "actions@github.com"
+      git config --global user.name "GitHub Action"
+    else
+      echo "GIT_IDENTITY must be either 'author' or 'actions'";
+      exit 1;
+    fi;
 }
 
 # Checks if any files are changed
@@ -26,44 +35,30 @@ _git_changed() {
     [[ -n "$(git status -s)" ]]
 }
 
-_git_changes() {
-    git diff
-}
-
 (
 # PROGRAM
 # Changing to the directory
-cd "$GITHUB_ACTION_PATH"
+if [ -z "$INPUT_WORKING_DIRECTORY" ] ; then
+  INPUT_WORKING_DIRECTORY=$GITHUB_ACTION_PATH
+fi
+cd "$INPUT_WORKING_DIRECTORY"
 
 echo "Installing prettier..."
 
-case $INPUT_WORKING_DIRECTORY in
-    false)
-        ;;
-    *)
-        cd $INPUT_WORKING_DIRECTORY
-        ;;
-esac
-
-case $INPUT_PRETTIER_VERSION in
-    false)
-        npm install --silent prettier
-        ;;
-    *)
-        npm install --silent prettier@$INPUT_PRETTIER_VERSION
-        ;;
-esac
+npm install --silent prettier@$INPUT_PRETTIER_VERSION
 
 # Install plugins
 if [ -n "$INPUT_PRETTIER_PLUGINS" ]; then
-    for plugin in $INPUT_PRETTIER_PLUGINS; do
-        echo "Checking plugin: $plugin"
-        # check regex against @prettier/xyz
-        if ! echo "$plugin" | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'; then
-            echo "$plugin does not seem to be a valid @prettier/plugin-x plugin. Exiting."
-            exit 1
-        fi
-    done
+    if [ "$INPUT_ALLOW_OTHER_PLUGINS" != "true" ]; then
+        for plugin in $INPUT_PRETTIER_PLUGINS; do
+            echo "Checking plugin: $plugin"
+            # check regex against @prettier/xyz
+            if ! echo "$plugin" | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'; then
+                echo "$plugin does not seem to be a valid @prettier/plugin-x plugin. Exiting."
+                exit 1
+            fi
+        done
+    fi
     npm install --silent $INPUT_PRETTIER_PLUGINS
 fi
 )
@@ -71,8 +66,8 @@ fi
 PRETTIER_RESULT=0
 echo "Prettifying files..."
 echo "Files:"
-prettier $INPUT_PRETTIER_OPTIONS \
-  || { PRETTIER_RESULT=$?; echo "Problem running prettier with $INPUT_PRETTIER_OPTIONS"; exit 1; }
+npx prettier $INPUT_PRETTIER_OPTIONS \
+  || { PRETTIER_RESULT=$?; echo "Problem running prettier with $INPUT_PRETTIER_OPTIONS"; exit 1; } >> $GITHUB_STEP_SUMMARY
 
 echo "Prettier result: $PRETTIER_RESULT"
 
@@ -87,42 +82,65 @@ if $INPUT_CLEAN_NODE_FOLDER; then
 fi
 
 if [ -f 'package-lock.json' ]; then
-  git checkout -- package-lock.json
+  git checkout -- package-lock.json || echo "No package-lock.json file tracked by git."
 else
   echo "No package-lock.json file."
 fi
 
+# If running under only_changed, reset every modified file that wasn't also modified in the last commit
+# This allows only_changed and dry to work together, and simplified the non-dry logic below
+if [ $INPUT_ONLY_CHANGED = true ] || [ $INPUT_ONLY_CHANGED_PR = true ] ; then
+  BASE_BRANCH=origin/$GITHUB_BASE_REF
+  if $INPUT_ONLY_CHANGED; then
+    BASE_BRANCH=HEAD~1
+  fi
+
+  echo "Resetting changes, removing changes to files not changed since $BASE_BRANCH"
+  # list of all files changed in the previous commit
+  git diff --name-only HEAD $BASE_BRANCH > /tmp/prev.txt
+  # list of all files with outstanding changes
+  git diff --name-only HEAD > /tmp/cur.txt
+
+  OLDIFS="$IFS"
+  IFS=$'\n'
+  # get all files that are in prev.txt that aren't also in cur.txt
+  for file in $(comm -1 -3 /tmp/prev.txt /tmp/cur.txt)
+  do
+    echo "resetting: $file"
+    git restore -- "$file"
+  done
+  IFS="$OLDIFS"
+fi
+
 # To keep runtime good, just continue if something was changed
 if _git_changed; then
   # case when --write is used with dry-run so if something is unpretty there will always have _git_changed
   if $INPUT_DRY; then
     echo "Unpretty Files Changes:"
-    _git_changes
-    echo "Finishing dry-run. Exiting before committing."
-    exit 1
+    git diff
+    if $INPUT_NO_COMMIT; then
+        echo "There are changes that won't be commited, you can use an external job to do so."
+    else
+        echo "Finishing dry-run. Exiting before committing."
+        exit 1
+    fi
   else
     # Calling method to configure the git environemnt
     _git_setup
 
-    if $INPUT_ONLY_CHANGED; then
-      # --diff-filter=d excludes deleted files
-      OLDIFS="$IFS"
-      IFS=$'\n'
-      for file in $(git diff --name-only --diff-filter=d HEAD^..HEAD)
-      do
-        git add "$file"
-      done
-      IFS="$OLDIFS"
-    else
-      # Add changes to git
-      git add "${INPUT_FILE_PATTERN}" || echo "Problem adding your files with pattern ${INPUT_FILE_PATTERN}"
+    # Add changes to git
+    git add "${INPUT_FILE_PATTERN}" || echo "Problem adding your files with pattern ${INPUT_FILE_PATTERN}"
+
+    if $INPUT_NO_COMMIT; then
+      echo "There are changes that won't be commited, you can use an external job to do so."
+      exit 0
     fi
 
     # Commit and push changes back
     if $INPUT_SAME_COMMIT; then
       echo "Amending the current commit..."
       git pull
-      git commit --amend --no-edit
+      git commit --amend --no-edit --allow-empty
       git push origin -f
     else
       if [ "$INPUT_COMMIT_DESCRIPTION" != "" ]; then

tests/integration_tests.bats

@@ -0,0 +1,195 @@
+#!/usr/bin/env bats
+
+# Integration tests for prettier_action
+# These tests verify the overall behavior of the action
+
+load 'test_helper'
+
+setup() {
+    setup_test_repo
+    mock_github_env
+    set_default_inputs
+    export SCRIPT_DIR="$(cd "$(dirname "${BATS_TEST_DIRNAME}")" && pwd)"
+}
+
+teardown() {
+    teardown_test_repo
+}
+
+@test "Action sets correct working directory when not specified" {
+    export INPUT_WORKING_DIRECTORY=""
+    export GITHUB_ACTION_PATH="/test/path"
+
+    # We'll test that the directory change logic works correctly
+    # by verifying the default assignment
+    result=$(bash -c '
+        INPUT_WORKING_DIRECTORY=""
+        GITHUB_ACTION_PATH="/test/path"
+        if [ -z "$INPUT_WORKING_DIRECTORY" ]; then
+            INPUT_WORKING_DIRECTORY=$GITHUB_ACTION_PATH
+        fi
+        echo "$INPUT_WORKING_DIRECTORY"
+    ')
+
+    [ "$result" = "/test/path" ]
+}
+
+@test "Action preserves working directory when specified" {
+    export INPUT_WORKING_DIRECTORY="/custom/path"
+
+    result=$(bash -c '
+        INPUT_WORKING_DIRECTORY="/custom/path"
+        GITHUB_ACTION_PATH="/test/path"
+        if [ -z "$INPUT_WORKING_DIRECTORY" ]; then
+            INPUT_WORKING_DIRECTORY=$GITHUB_ACTION_PATH
+        fi
+        echo "$INPUT_WORKING_DIRECTORY"
+    ')
+
+    [ "$result" = "/custom/path" ]
+}
+
+@test "Clean node folder removes node_modules when it exists" {
+    # Create node_modules directory
+    mkdir -p node_modules
+    echo "test" > node_modules/test.txt
+
+    # Simulate the clean logic
+    INPUT_CLEAN_NODE_FOLDER=true
+    if $INPUT_CLEAN_NODE_FOLDER; then
+        if [ -d 'node_modules' ]; then
+            rm -r node_modules/
+        fi
+    fi
+
+    # Verify node_modules was removed
+    [ ! -d "node_modules" ]
+}
+
+@test "Clean node folder handles missing node_modules gracefully" {
+    # Ensure no node_modules exists
+    [ ! -d "node_modules" ]
+
+    # Simulate the clean logic
+    INPUT_CLEAN_NODE_FOLDER=true
+    run bash -c '
+        if $INPUT_CLEAN_NODE_FOLDER; then
+            if [ -d "node_modules" ]; then
+                rm -r node_modules/
+                echo "Deleted"
+            else
+                echo "No node_modules/ folder."
+            fi
+        fi
+    '
+
+    [ "$status" -eq 0 ]
+    [[ "$output" =~ "No node_modules/ folder." ]]
+}
+
+@test "Package-lock.json is restored when it exists" {
+    # Create a package-lock.json and commit it
+    echo '{"name": "test"}' > package-lock.json
+    git add package-lock.json
+    git commit -m "Add package-lock.json"
+
+    # Modify it
+    echo '{"name": "modified"}' > package-lock.json
+
+    # Restore it using git checkout
+    git checkout -- package-lock.json
+
+    # Verify it was restored
+    content=$(cat package-lock.json)
+    [[ "$content" =~ '"name": "test"' ]]
+}
+
+@test "Package-lock.json restore handles missing file gracefully" {
+    # Ensure no package-lock.json exists
+    [ ! -f "package-lock.json" ]
+
+    # Try to restore (should not fail)
+    run bash -c '
+        if [ -f "package-lock.json" ]; then
+            git checkout -- package-lock.json || echo "No package-lock.json file tracked by git."
+        else
+            echo "No package-lock.json file."
+        fi
+    '
+
+    [ "$status" -eq 0 ]
+    [[ "$output" =~ "No package-lock.json file." ]]
+}
+
+@test "File pattern logic for only_changed mode filters correctly" {
+    # Create initial commit
+    echo "file1" > file1.txt
+    echo "file2" > file2.txt
+    git add .
+    git commit -m "Initial commit"
+
+    # Modify only file1
+    echo "modified" > file1.txt
+    git add file1.txt
+    git commit -m "Modify file1"
+
+    # Modify both files
+    echo "changed1" > file1.txt
+    echo "changed2" > file2.txt
+
+    # Get files changed in previous commit
+    git diff --name-only HEAD HEAD~1 > /tmp/prev.txt
+
+    # Get files with current changes
+    git diff --name-only HEAD > /tmp/cur.txt
+
+    # Verify file1.txt is in prev.txt (it was changed in last commit)
+    run grep "file1.txt" /tmp/prev.txt
+    [ "$status" -eq 0 ]
+
+    # Verify both files are in cur.txt (both have current changes)
+    run grep "file1.txt" /tmp/cur.txt
+    [ "$status" -eq 0 ]
+    run grep "file2.txt" /tmp/cur.txt
+    [ "$status" -eq 0 ]
+
+    # Files in cur.txt but not in prev.txt should be reset
+    # In this case, file2.txt should be reset
+    for file in $(comm -1 -3 /tmp/prev.txt /tmp/cur.txt); do
+        [ "$file" = "file2.txt" ]
+    done
+}
+
+@test "Dry run mode detects unpretty files" {
+    # This tests the logic flow for dry run
+    # We simulate detecting changes
+
+    # Create a test file
+    echo "test" > test.txt
+
+    # Simulate git detecting changes
+    run bash -c '
+        source tests/test_helper.bash
+        setup_test_repo
+        echo "test" > test.txt
+        _git_changed
+    '
+
+    [ "$status" -eq 0 ]
+}
+
+@test "No changes scenario is handled correctly" {
+    # Create and commit a file
+    echo "test" > test.txt
+    git add test.txt
+    git commit -m "Add test file"
+
+    # Verify no changes
+    run bash -c '
+        source tests/test_helper.bash
+        load_script_functions entrypoint.sh
+        _git_changed
+    '
+
+    [ "$status" -eq 1 ]
+}

tests/plugin_validation_tests.bats

@@ -0,0 +1,99 @@
+#!/usr/bin/env bats
+
+# Integration tests for prettier plugin validation
+
+load 'test_helper'
+
+setup() {
+    setup_test_repo
+    mock_github_env
+    set_default_inputs
+}
+
+teardown() {
+    teardown_test_repo
+}
+
+# Test valid prettier plugin patterns
+@test "Valid @prettier/plugin-* format should pass validation" {
+    # Test the regex pattern used in entrypoint.sh
+    plugin="@prettier/plugin-php"
+
+    run bash -c "echo '$plugin' | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'"
+
+    [ "$status" -eq 0 ]
+}
+
+@test "Valid prettier-plugin-* format should pass validation" {
+    plugin="prettier-plugin-java"
+
+    run bash -c "echo '$plugin' | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'"
+
+    [ "$status" -eq 0 ]
+}
+
+@test "Valid @scope/prettier-plugin-* format should pass validation" {
+    plugin="@company/prettier-plugin-custom"
+
+    run bash -c "echo '$plugin' | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'"
+
+    [ "$status" -eq 0 ]
+}
+
+@test "Invalid plugin name should fail validation" {
+    plugin="some-random-package"
+
+    run bash -c "echo '$plugin' | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'"
+
+    [ "$status" -eq 1 ]
+}
+
+@test "Invalid plugin with wrong prefix should fail validation" {
+    plugin="@other/plugin-something"
+
+    run bash -c "echo '$plugin' | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'"
+
+    [ "$status" -eq 1 ]
+}
+
+@test "Multiple valid plugins should all pass validation" {
+    plugins="@prettier/plugin-php prettier-plugin-java @scope/prettier-plugin-custom"
+
+    for plugin in $plugins; do
+        run bash -c "echo '$plugin' | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'"
+        [ "$status" -eq 0 ]
+    done
+}
+
+@test "Plugin name with uppercase should fail validation" {
+    plugin="@prettier/plugin-PHP"
+
+    run bash -c "echo '$plugin' | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'"
+
+    [ "$status" -eq 1 ]
+}
+
+@test "Plugin name with numbers or underscores should fail validation" {
+    plugin1="@prettier/plugin-test123"
+    plugin2="prettier-plugin-test_name"
+
+    run bash -c "echo '$plugin1' | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'"
+    [ "$status" -eq 1 ]
+
+    run bash -c "echo '$plugin2' | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'"
+    [ "$status" -eq 1 ]
+}
+
+@test "Official prettier plugins should be recognized" {
+    # List of known official prettier plugins
+    plugins=(
+        "@prettier/plugin-php"
+        "@prettier/plugin-ruby"
+        "@prettier/plugin-xml"
+    )
+
+    for plugin in "${plugins[@]}"; do
+        run bash -c "echo '$plugin' | grep -Eq '(@prettier\/plugin-|(@[a-z\-]+\/)?prettier-plugin-){1}([a-z\-]+)'"
+        [ "$status" -eq 0 ]
+    done
+}

tests/run_tests.sh

@@ -0,0 +1,115 @@
+#!/usr/bin/env bash
+
+# Test runner script for prettier_action
+# This script installs BATS and runs all tests
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+BATS_VERSION="v1.11.0"
+BATS_INSTALL_DIR="$SCRIPT_DIR/bats"
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m' # No Color
+
+echo "========================================="
+echo "Prettier Action Test Runner"
+echo "========================================="
+echo ""
+
+# Function to install BATS
+install_bats() {
+    echo -e "${YELLOW}Installing BATS (Bash Automated Testing System)...${NC}"
+
+    if [ -d "$BATS_INSTALL_DIR" ]; then
+        echo "BATS already installed at $BATS_INSTALL_DIR"
+        return 0
+    fi
+
+    # Clone BATS
+    git clone --depth 1 --branch "$BATS_VERSION" https://github.com/bats-core/bats-core.git "$BATS_INSTALL_DIR"
+
+    # Clone support libraries
+    mkdir -p "$BATS_INSTALL_DIR/test_helper"
+    git clone --depth 1 https://github.com/bats-core/bats-support.git "$BATS_INSTALL_DIR/test_helper/bats-support"
+    git clone --depth 1 https://github.com/bats-core/bats-assert.git "$BATS_INSTALL_DIR/test_helper/bats-assert"
+
+    echo -e "${GREEN}BATS installed successfully!${NC}"
+    echo ""
+}
+
+# Function to check if BATS is available
+check_bats() {
+    if [ -x "$BATS_INSTALL_DIR/bin/bats" ]; then
+        return 0
+    fi
+    return 1
+}
+
+# Main execution
+main() {
+    cd "$PROJECT_ROOT"
+
+    # Check if BATS is installed, if not install it
+    if ! check_bats; then
+        install_bats
+    fi
+
+    echo -e "${YELLOW}Running tests...${NC}"
+    echo ""
+
+    # Run all test files
+    TEST_FILES=(
+        "$SCRIPT_DIR/unit_tests.bats"
+        "$SCRIPT_DIR/plugin_validation_tests.bats"
+        "$SCRIPT_DIR/integration_tests.bats"
+    )
+
+    FAILED=0
+
+    for test_file in "${TEST_FILES[@]}"; do
+        if [ -f "$test_file" ]; then
+            echo "Running $(basename "$test_file")..."
+            if "$BATS_INSTALL_DIR/bin/bats" "$test_file"; then
+                echo -e "${GREEN}✓ $(basename "$test_file") passed${NC}"
+            else
+                echo -e "${RED}✗ $(basename "$test_file") failed${NC}"
+                FAILED=1
+            fi
+            echo ""
+        fi
+    done
+
+    echo "========================================="
+    if [ $FAILED -eq 0 ]; then
+        echo -e "${GREEN}All tests passed!${NC}"
+        exit 0
+    else
+        echo -e "${RED}Some tests failed!${NC}"
+        exit 1
+    fi
+}
+
+# Parse command line arguments
+case "${1:-}" in
+    --install-only)
+        install_bats
+        exit 0
+        ;;
+    --help)
+        echo "Usage: $0 [OPTIONS]"
+        echo ""
+        echo "Options:"
+        echo "  --install-only    Only install BATS without running tests"
+        echo "  --help            Show this help message"
+        echo ""
+        exit 0
+        ;;
+    *)
+        main
+        ;;
+esac

tests/test_helper.bash

@@ -0,0 +1,78 @@
+#!/usr/bin/env bash
+
+# Test helper functions for prettier_action tests
+
+# Set up a temporary test directory
+setup_test_repo() {
+    export TEST_TEMP_DIR="$(mktemp -d)"
+    cd "$TEST_TEMP_DIR" || exit 1
+    git init
+    git config user.name "Test User"
+    git config user.email "test@example.com"
+}
+
+# Clean up temporary test directory
+teardown_test_repo() {
+    if [ -n "$TEST_TEMP_DIR" ] && [ -d "$TEST_TEMP_DIR" ]; then
+        rm -rf "$TEST_TEMP_DIR"
+    fi
+}
+
+# Create a sample file for testing
+create_sample_file() {
+    local filename="${1:-test.js}"
+    local content="${2:-const x=1;const y=2;}"
+    echo "$content" > "$filename"
+}
+
+# Create a sample package.json
+create_package_json() {
+    cat > package.json << 'EOF'
+{
+  "name": "test-project",
+  "version": "1.0.0",
+  "description": "Test project"
+}
+EOF
+}
+
+# Mock git environment variables for GitHub Actions
+mock_github_env() {
+    export GITHUB_ACTOR="${GITHUB_ACTOR:-test-actor}"
+    export GITHUB_ACTOR_ID="${GITHUB_ACTOR_ID:-12345}"
+    export GITHUB_ACTION_PATH="${GITHUB_ACTION_PATH:-/app}"
+    export GITHUB_BASE_REF="${GITHUB_BASE_REF:-main}"
+    export GITHUB_STEP_SUMMARY="${GITHUB_STEP_SUMMARY:-/dev/null}"
+    export INPUT_GITHUB_TOKEN="${INPUT_GITHUB_TOKEN:-test-token}"
+}
+
+# Set default input environment variables
+set_default_inputs() {
+    export INPUT_WORKING_DIRECTORY="${INPUT_WORKING_DIRECTORY:-}"
+    export INPUT_PRETTIER_VERSION="${INPUT_PRETTIER_VERSION:-latest}"
+    export INPUT_PRETTIER_OPTIONS="${INPUT_PRETTIER_OPTIONS:---write **/*.js}"
+    export INPUT_PRETTIER_PLUGINS="${INPUT_PRETTIER_PLUGINS:-}"
+    export INPUT_ALLOW_OTHER_PLUGINS="${INPUT_ALLOW_OTHER_PLUGINS:-false}"
+    export INPUT_CLEAN_NODE_FOLDER="${INPUT_CLEAN_NODE_FOLDER:-true}"
+    export INPUT_ONLY_CHANGED="${INPUT_ONLY_CHANGED:-false}"
+    export INPUT_ONLY_CHANGED_PR="${INPUT_ONLY_CHANGED_PR:-false}"
+    export INPUT_FILE_PATTERN="${INPUT_FILE_PATTERN:-*}"
+    export INPUT_DRY="${INPUT_DRY:-false}"
+    export INPUT_NO_COMMIT="${INPUT_NO_COMMIT:-false}"
+    export INPUT_SAME_COMMIT="${INPUT_SAME_COMMIT:-false}"
+    export INPUT_COMMIT_MESSAGE="${INPUT_COMMIT_MESSAGE:-Automated formatting}"
+    export INPUT_COMMIT_DESCRIPTION="${INPUT_COMMIT_DESCRIPTION:-}"
+    export INPUT_COMMIT_OPTIONS="${INPUT_COMMIT_OPTIONS:-}"
+    export INPUT_PUSH_OPTIONS="${INPUT_PUSH_OPTIONS:-}"
+    export INPUT_GIT_IDENTITY="${INPUT_GIT_IDENTITY:-actions}"
+}
+
+# Load a bash script without executing it (for testing functions)
+load_script_functions() {
+    local script_path="$1"
+    # Source only the function definitions, not the main program
+    # We extract functions by finding lines between function definitions and the main program block
+    sed -n '/^_git_setup/,/^}/p' "$script_path" > "$TEST_TEMP_DIR/functions.sh"
+    sed -n '/^_git_changed/,/^}/p' "$script_path" >> "$TEST_TEMP_DIR/functions.sh"
+    source "$TEST_TEMP_DIR/functions.sh"
+}

tests/unit_tests.bats

@@ -0,0 +1,124 @@
+#!/usr/bin/env bats
+
+# Unit tests for prettier_action entrypoint.sh functions
+
+load 'test_helper'
+
+setup() {
+    setup_test_repo
+    mock_github_env
+    set_default_inputs
+
+    # Load the functions from entrypoint.sh
+    export SCRIPT_DIR="$(cd "$(dirname "${BATS_TEST_DIRNAME}")" && pwd)"
+    load_script_functions "$SCRIPT_DIR/entrypoint.sh"
+}
+
+teardown() {
+    teardown_test_repo
+}
+
+# Test _git_setup function with 'actions' identity
+@test "_git_setup creates .netrc file with correct permissions" {
+    export INPUT_GIT_IDENTITY="actions"
+
+    run _git_setup
+
+    [ "$status" -eq 0 ]
+    [ -f "$HOME/.netrc" ]
+
+    # Check file permissions (should be 600)
+    local perms=$(stat -c "%a" "$HOME/.netrc")
+    [ "$perms" = "600" ]
+}
+
+@test "_git_setup configures git with 'actions' identity" {
+    export INPUT_GIT_IDENTITY="actions"
+
+    run _git_setup
+
+    [ "$status" -eq 0 ]
+
+    # Check git config
+    local git_name=$(git config --global user.name)
+    local git_email=$(git config --global user.email)
+
+    [ "$git_name" = "GitHub Action" ]
+    [ "$git_email" = "actions@github.com" ]
+}
+
+@test "_git_setup configures git with 'author' identity" {
+    export INPUT_GIT_IDENTITY="author"
+    export GITHUB_ACTOR="test-user"
+    export GITHUB_ACTOR_ID="54321"
+
+    run _git_setup
+
+    [ "$status" -eq 0 ]
+
+    # Check git config
+    local git_name=$(git config --global user.name)
+    local git_email=$(git config --global user.email)
+
+    [ "$git_name" = "test-user" ]
+    [ "$git_email" = "54321+test-user@users.noreply.github.com" ]
+}
+
+@test "_git_setup fails with invalid identity" {
+    export INPUT_GIT_IDENTITY="invalid"
+
+    run _git_setup
+
+    [ "$status" -eq 1 ]
+    [[ "$output" =~ "GIT_IDENTITY must be either 'author' or 'actions'" ]]
+}
+
+@test "_git_changed returns true when files are modified" {
+    # Create and commit a file
+    echo "test" > test.txt
+    git add test.txt
+    git commit -m "Initial commit"
+
+    # Modify the file
+    echo "modified" > test.txt
+
+    run _git_changed
+
+    [ "$status" -eq 0 ]
+}
+
+@test "_git_changed returns false when no files are modified" {
+    # Create and commit a file
+    echo "test" > test.txt
+    git add test.txt
+    git commit -m "Initial commit"
+
+    # No modifications
+    run _git_changed
+
+    [ "$status" -eq 1 ]
+}
+
+@test "_git_changed returns true for untracked files" {
+    # Create a file without committing
+    echo "test" > untracked.txt
+
+    run _git_changed
+
+    [ "$status" -eq 0 ]
+}
+
+@test "_git_changed returns true for staged files" {
+    # Create and commit a file
+    echo "test" > test.txt
+    git add test.txt
+    git commit -m "Initial commit"
+
+    # Add a new file and stage it
+    echo "new file" > new.txt
+    git add new.txt
+
+    run _git_changed
+
+    [ "$status" -eq 0 ]
+}