diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..e9a90e6
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,33 @@
+name: Test repocopy
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  bash-tests:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install dependencies
+        run: sudo apt update && sudo apt install -y jq xclip bats
+      - name: Run Bash tests
+        run: bats tests/bash/rpcp.bats
+
+  pester-tests:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install PowerShell & Pester
+        uses: actions/setup-python@v4   # just to get pwsh; GitHub image already has pwsh
+      - name: Install Pester
+        shell: pwsh
+        run: |
+          Install-Module Pester -Force -Scope CurrentUser
+      - name: Run PowerShell tests
+        shell: pwsh
+        run: |
+          Invoke-Pester -Path tests/powershell -CI -Output Detailed
+      
\ No newline at end of file
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..367a773
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,6 @@
+[submodule "tests/test_helper/bats-support"]
+	path = tests/test_helper/bats-support
+	url = https://github.com/bats-core/bats-support
+[submodule "tests/test_helper/bats-assert"]
+	path = tests/test_helper/bats-assert
+	url = https://github.com/bats-core/bats-assert
diff --git a/README.md b/README.md
index f1c2313..592b0ab 100644
--- a/README.md
+++ b/README.md
@@ -155,9 +155,22 @@ After running `rpcp`, your clipboard contains all relevant files with context. P
 
 ## 🧪 Testing & Linting
 
-- **Pester**: Write tests for PowerShell functions.
-- **PSScriptAnalyzer**: Validate PowerShell style.
-- **ShellCheck**: Lint the Bash script.
+# Running tests locally
+
+## Bash (Bats)
+
+```bash
+sudo apt install bats jq xclip   # or the equivalent for your OS
+bats tests/bash/repocopy.bats
+```
+
+## PowerShell (Pester)
+
+```
+Install-Module Pester -Force -Scope CurrentUser  # once
+Invoke-Pester -Path tests/powershell -Output Detailed
+```
+
 
 ---
 
diff --git a/config.json b/config.json
index b73a18b..66d820b 100644
--- a/config.json
+++ b/config.json
@@ -1,8 +1,9 @@
 {
     "repoPath": ".",
     "maxFileSize": 204800,
-    "ignoreFolders": [".git", ".github", ".terraform", "node_modules","plugin-cache", "terraform-provider*", "logo-drafts","build", ".archive"],
+    "ignoreFolders": [".git", ".github", ".terraform", "node_modules","plugin-cache", "terraform-provider*", "logo-drafts","build", ".archive","test_helper"],
     "ignoreFiles": ["manifest.json", "package-lock.json","*.png","*.jpg","*.jpeg","*.gif","*.svg","*.zip","*.tar.gz","*.tgz","*.tfstate", "*.tfstate.backup", "*.tfvars", "*.tfvars.json", "*.tfplan", "*.tfplan.json","*.avif","*.webp"],
+    "replacements": { "PARENT_COMPANY":"pca","Bob":"Redacted_name","PROJECT_ACRONYM":"wla" },
     "replacements": { "PARENT_COMPANY":"pca","CLIENT_NAME":"ClientName","PROJECT_ACRONYM":"wla" },
     "showCopiedFiles": true,
     "autoInstallDeps": true
diff --git a/rpcp.ps1 b/rpcp.ps1
index 78fb070..5385fbd 100644
--- a/rpcp.ps1
+++ b/rpcp.ps1
@@ -71,14 +71,16 @@ Param(
     [long]     $MaxFileSize,
 
     [Parameter()]
-    [ValidateNotNullOrEmpty()]
+    [AllowNull()]
     [string[]] $IgnoreFolders,
 
     [Parameter()]
-    [ValidateNotNullOrEmpty()]
+    [AllowNull()]
     [string[]] $IgnoreFiles,
 
     [Parameter()]
+    [AllowNull()]
+
     [hashtable]$Replacements,
 
     [Parameter()]
@@ -103,17 +105,20 @@ function Get-Config {
 function Get-FilesToInclude {
     [CmdletBinding()]
     Param(
-        [Parameter(Mandatory)]
+        [Parameter()]
         [ValidateScript({ Test-Path $_ -PathType Container })]
         [string]   $RepoRoot,
 
-        [Parameter(Mandatory)]
-        [string[]] $IgnoreFolders,
+        # ↓↓↓ CHANGE #1 – remove Mandatory, give default @()
+        [Parameter()]
+        [string[]] $IgnoreFolders = @(),
 
-        [Parameter(Mandatory)]
-        [string[]] $IgnoreFiles,
+        # ↓↓↓ CHANGE #2 – remove Mandatory, give default @()
+        [Parameter()]
+        [string[]] $IgnoreFiles   = @(),
+
+        [Parameter()]
 
-        [Parameter(Mandatory)]
         [ValidateRange(0, [long]::MaxValue)]
         [long]     $MaxFileSize
     )
@@ -125,8 +130,15 @@ function Get-FilesToInclude {
         # Folder pattern check
         $dirs = $f.DirectoryName.Split([IO.Path]::DirectorySeparatorChar)
         foreach ($pat in $IgnoreFolders) {
-            if ($dirs -like $pat) {
-                $reason = "matched ignore-folder '$pat'"; break
+            $sepRegex   = [Regex]::Escape([IO.Path]::DirectorySeparatorChar)
+            $segments   = $f.DirectoryName -split $sepRegex      # safe on Win & *nix
+    
+            foreach ($pat in $IgnoreFolders) {
+                if ($segments -like $pat) {
+                    $reason = "matched ignore-folder '$pat'"
+                    break
+                }
+
             }
         }
         # File name check
@@ -228,15 +240,27 @@ $config = Get-Config -ConfigFilePath $ConfigFile
 # Merge CLI parameters over config values
 $rp = if ($PSBoundParameters.ContainsKey('RepoPath')) { $RepoPath } else { $config.repoPath }
 $mf = if ($PSBoundParameters.ContainsKey('MaxFileSize')) { $MaxFileSize } else { [long]$config.maxFileSize }
-$if = if ($PSBoundParameters.ContainsKey('IgnoreFolders')) { $IgnoreFolders } else { @($config.ignoreFolders) }
-$ifl = if ($PSBoundParameters.ContainsKey('IgnoreFiles')) { $IgnoreFiles } else { @($config.ignoreFiles) }
+$if  = if ($PSBoundParameters.ContainsKey('IgnoreFolders') -and $IgnoreFolders) { $IgnoreFolders } else { @($config.ignoreFolders) }
+$ifl = if ($PSBoundParameters.ContainsKey('IgnoreFiles')   -and $IgnoreFiles)   { $IgnoreFiles }   else { @($config.ignoreFiles) }
 $rep = if ($PSBoundParameters.ContainsKey('Replacements')) { $Replacements } else {
     $h = @{}; foreach ($p in $config.replacements.PSObject.Properties) { $h[$p.Name] = $p.Value }; $h
 }
-$scf = if ($PSBoundParameters.ContainsKey('ShowCopiedFiles')) { $ShowCopiedFiles.IsPresent } else { [bool]$config.showCopiedFiles }
+$scf = if ($PSBoundParameters.ContainsKey('ShowCopiedFiles')) {
+    $ShowCopiedFiles.IsPresent
+ } else {
+    [bool]$config.showCopiedFiles
+ }
+
+if ($null -eq $if)  { $if  = @() }
+if ($null -eq $ifl) { $ifl = @() }
 
 # Gather, filter, and log
-$filesToCopy = Get-FilesToInclude -RepoRoot $rp -IgnoreFolders $if -IgnoreFiles $ifl -MaxFileSize $mf
+$filesToCopy = Get-FilesToInclude `
+           -RepoRoot      $rp `
+           -IgnoreFolders $if `
+           -IgnoreFiles   $ifl `
+           -MaxFileSize   $mf
+
 
 if ($filesToCopy.Count -eq 0) {
     Write-Warning 'No files passed the filters; nothing to copy.'
diff --git a/tests/bash/rpcp.bats b/tests/bash/rpcp.bats
new file mode 100644
index 0000000..2421898
--- /dev/null
+++ b/tests/bash/rpcp.bats
@@ -0,0 +1,111 @@
+#!/usr/bin/env bats
+#
+# End-to-end tests for the Bash version of repocopy (rpcp.sh)
+# ─────────────────────────────────────────────────────────────
+# • Spins-up a temp repo each run (safe & hermetic)
+# • Stubs xclip/pbcopy so we can inspect what hits the clipboard
+# • Verifies:
+#     1. happy-path copy & token replacement
+#     2. max-file-size exclusion
+#     3. override of max-file-size via CLI
+#     4. folder-ignore pattern ("build")
+#     5. behaviour when --show-copied-files is used
+#
+export BATS_LIB_PATH="$PWD/tests/test_helper"
+load 'test_helper/bats-support/load'
+load 'test_helper/bats-assert/load'
+
+setup() {
+  # ── ① disposable sandbox repo ──────────────────────────────
+  TMP_REPO="$(mktemp -d)"
+  mkdir -p "$TMP_REPO/src" "$TMP_REPO/build"
+
+  # source files
+  printf 'hello ClientName\n' >"$TMP_REPO/src/include.txt"
+  printf 'ignore me\n'        >"$TMP_REPO/manifest.json"
+  head  -c 10 </dev/urandom  >"$TMP_REPO/image.png"
+
+  # a 300-KiB file to test the size filter
+  dd if=/dev/zero of="$TMP_REPO/src/big.bin" bs=1k count=300 2>/dev/null
+
+  # something inside an ignored folder
+  printf 'ignore me\n' >"$TMP_REPO/build/output.txt"
+
+  # config.json that matches the Pester suite
+  cat >"$TMP_REPO/config.json" <<'JSON'
+{
+  "repoPath": ".",
+  "maxFileSize": 204800,
+  "ignoreFolders": [ "build" ],
+  "ignoreFiles": [ "manifest.json", "*.png", "config.json" ],
+  "replacements": { "ClientName": "Bob" },
+  "showCopiedFiles": false,
+  "autoInstallDeps": false
+}
+JSON
+
+  # ── ② stub clipboard (xclip) ───────────────────────────────
+  CLIP_FILE="$(mktemp)"
+  STUB_DIR="$(mktemp -d)"
+  cat >"$STUB_DIR/xclip" <<STUB
+#!/usr/bin/env bash
+cat > "$CLIP_FILE"
+STUB
+  chmod +x "$STUB_DIR/xclip"
+  PATH="$STUB_DIR:$PATH"
+}
+
+teardown() {
+  rm -rf "$TMP_REPO" "$CLIP_FILE" "$STUB_DIR"
+}
+
+# helper to run rpcp.sh and slurp clipboard into $CLIP variable
+run_rpcp() {
+  run bash ./rpcp.sh "$@"
+  # copy the clipboard text into a shell variable for assertions
+  CLIP="$(cat "$CLIP_FILE")"
+}
+
+# ─────────────────────────────────────────────────────────────
+@test "default run: copies only permitted files & replaces tokens" {
+  run_rpcp --repo-path "$TMP_REPO" --config-file "$TMP_REPO/config.json"
+
+  assert_success
+  assert_line --partial "✅ Copied"    # sanity
+
+  assert_regex "$CLIP" "include\\.txt"
+  assert_regex "$CLIP" "hello Bob"
+
+  refute_regex "$CLIP" "manifest\\.json"
+  refute_regex "$CLIP" "image\\.png"
+  refute_regex "$CLIP" "config\\.json"
+  refute_regex "$CLIP" "output\\.txt"
+  refute_regex "$CLIP" "big\\.bin"
+}
+
+@test "size filter: big.bin is excluded by default" {
+  run_rpcp --repo-path "$TMP_REPO" --config-file "$TMP_REPO/config.json"
+  refute_regex "$CLIP" "big\\.bin"
+}
+
+@test "size override: big.bin appears when --max-file-size 0 is used" {
+  run_rpcp --repo-path "$TMP_REPO" \
+           --config-file "$TMP_REPO/config.json" \
+           --max-file-size 0
+  assert_regex "$CLIP" "big\\.bin"
+}
+
+@test "folder ignore: anything under build/ is skipped" {
+  run_rpcp --repo-path "$TMP_REPO" --config-file "$TMP_REPO/config.json"
+  refute_regex "$CLIP" "build/output\\.txt"
+}
+
+@test "--show-copied-files does not affect clipboard content" {
+  run_rpcp --repo-path "$TMP_REPO" \
+           --config-file "$TMP_REPO/config.json" \
+           --show-copied-files
+
+  # The script prints the file list to stdout;
+  # we just need to ensure normal data is still on the clipboard
+  assert_regex "$CLIP" "include\\.txt"
+}
diff --git a/tests/fixtures/sample-repo/build/output.txt b/tests/fixtures/sample-repo/build/output.txt
new file mode 100644
index 0000000..f709266
--- /dev/null
+++ b/tests/fixtures/sample-repo/build/output.txt
@@ -0,0 +1 @@
+ignore me
diff --git a/tests/fixtures/sample-repo/config.json b/tests/fixtures/sample-repo/config.json
new file mode 100644
index 0000000..c891671
--- /dev/null
+++ b/tests/fixtures/sample-repo/config.json
@@ -0,0 +1,8 @@
+{
+  "repoPath": ".",
+  "maxFileSize": 204800,
+  "ignoreFolders": [ "build" ],
+  "ignoreFiles"  : [ "manifest.json", "*.png", "config.json" ],
+  "replacements" : { "ClientName": "Bob" },
+  "showCopiedFiles": false
+}
diff --git a/tests/fixtures/sample-repo/image.png b/tests/fixtures/sample-repo/image.png
new file mode 100644
index 0000000..df93f5f
Binary files /dev/null and b/tests/fixtures/sample-repo/image.png differ
diff --git a/tests/fixtures/sample-repo/manifest.json b/tests/fixtures/sample-repo/manifest.json
new file mode 100644
index 0000000..c1c52bb
--- /dev/null
+++ b/tests/fixtures/sample-repo/manifest.json
@@ -0,0 +1 @@
+{ "note": "this file should be ignored by rpcp" }
diff --git a/tests/fixtures/sample-repo/src/big.bin b/tests/fixtures/sample-repo/src/big.bin
new file mode 100644
index 0000000..108b5ab
Binary files /dev/null and b/tests/fixtures/sample-repo/src/big.bin differ
diff --git a/tests/fixtures/sample-repo/src/include.txt b/tests/fixtures/sample-repo/src/include.txt
new file mode 100644
index 0000000..cc9d96b
--- /dev/null
+++ b/tests/fixtures/sample-repo/src/include.txt
@@ -0,0 +1 @@
+hello Bob
diff --git a/tests/powershell/rpcp.tests.ps1 b/tests/powershell/rpcp.tests.ps1
new file mode 100644
index 0000000..8c876e3
--- /dev/null
+++ b/tests/powershell/rpcp.tests.ps1
@@ -0,0 +1,146 @@
+# Pester 5 tests for repocopy (PowerShell edition)
+# ──────────────────────────────────────────────────────────────
+Import-Module Pester                          -ErrorAction Stop
+Import-Module Microsoft.PowerShell.Management -Force        # Set-Clipboard
+
+$ErrorActionPreference = 'Stop'
+
+Describe 'rpcp.ps1 end-to-end behaviour (fixture repo)' {
+
+    # ──────────────────────────────────────────────────────────
+    # ❶ Shared one-time setup
+    # ──────────────────────────────────────────────────────────
+    BeforeAll {
+        $ProjectRoot = (Resolve-Path "$PSScriptRoot/../../").Path
+        $Script      = Join-Path $ProjectRoot 'rpcp.ps1'
+        $FixtureRoot = Join-Path $ProjectRoot 'tests/fixtures/sample-repo'
+
+        # -- ensure fixture tree exists (idempotent) ------------------------
+        if (-not (Test-Path $FixtureRoot)) {
+            New-Item -ItemType Directory -Path "$FixtureRoot/src" -Force | Out-Null
+        }
+        
+        # minimal source file & image (re-create only if missing)
+        if (-not (Test-Path "$FixtureRoot/src/include.txt")) {
+            'hello ClientName' | Set-Content "$FixtureRoot/src/include.txt"
+        }
+        if (-not (Test-Path "$FixtureRoot/manifest.json")) {
+            '{ "note":"ignore" }' | Set-Content "$FixtureRoot/manifest.json"
+        }
+        if (-not (Test-Path "$FixtureRoot/image.png")) {
+            [IO.File]::WriteAllBytes("$FixtureRoot/image.png",[byte[]](0..9))
+        }
+        @'
+{
+  "repoPath": ".",
+  "maxFileSize": 204800,
+  "ignoreFolders": [ "build" ],
+  "ignoreFiles"  : [ "manifest.json", "*.png", "config.json" ],
+  "replacements" : { "ClientName": "Bob" },
+  "showCopiedFiles": false
+}
+'@ | Set-Content "$FixtureRoot/config.json"
+        # -- extra files for later tests -----------------------------------
+        if (-not (Test-Path "$FixtureRoot/src/big.bin")) {
+            $size  = 300kb            # 300 KiB  >  maxFileSize
+            $bytes = New-Object byte[] $size
+            [System.Random]::new().NextBytes($bytes)
+            [IO.File]::WriteAllBytes("$FixtureRoot/src/big.bin", $bytes)
+        }
+
+        if (-not (Test-Path "$FixtureRoot/build")) {
+            New-Item -ItemType Directory -Path "$FixtureRoot/build" | Out-Null
+            'ignore me' | Set-Content "$FixtureRoot/build/output.txt"
+        }
+
+        # -- helper: run rpcp & capture what it puts on the clipboard -------
+        # ── helper: run rpcp & capture what it puts on the clipboard ─────────────
+function Invoke-Rpcp {
+    [CmdletBinding()]
+    param(
+        [Parameter(Mandatory)]
+        [hashtable]$Param
+    )
+
+    Mock Set-Clipboard {
+        param($Value)
+        # flatten any array → single string so tests are simpler
+        Set-Variable -Name CapturedClipboard `
+                     -Value ($Value -join "`n") `
+                     -Scope Global
+    }
+
+    & $Script @Param | Out-Null
+
+    # copy-out *before* we purge the global
+    $result = $CapturedClipboard
+    Remove-Variable -Name CapturedClipboard -Scope Global -ErrorAction SilentlyContinue
+    return $result
+}
+
+    }
+
+    # ──────────────────────────────────────────────────────────
+    Context 'Default run (config.json only)' {
+        It 'copies only permitted files and performs replacements' {
+            $copied = Invoke-Rpcp -Param @{
+                RepoPath   = $FixtureRoot
+                ConfigFile = "$FixtureRoot/config.json"
+            }
+
+            $copied | Should -Match    'include\.txt'
+            $copied | Should -Match    'hello Bob'
+
+            $copied | Should -Not -Match 'manifest\.json'
+            $copied | Should -Not -Match 'image\.png'
+            $copied | Should -Not -Match 'config\.json'
+            $copied | Should -Not -Match 'output\.txt'
+            $copied | Should -Not -Match 'big\.bin'
+        }
+    }
+
+    Context 'Max file-size filter' {
+        It 'excludes files bigger than maxFileSize' {
+            $copied = Invoke-Rpcp -Param @{
+                RepoPath   = $FixtureRoot
+                ConfigFile = "$FixtureRoot/config.json"   # 204 KB limit
+            }
+
+            $copied | Should -Not -Match 'big\.bin'
+        }
+
+        It 'includes big file when CLI overrides maxFileSize' {
+            $copied = Invoke-Rpcp -Param @{
+                RepoPath    = $FixtureRoot
+                ConfigFile  = "$FixtureRoot/config.json"
+                MaxFileSize = 0          # disable size filtering
+            }
+
+            $copied | Should -Match 'big\.bin'
+        }
+    }
+
+    Context 'Folder ignore pattern' {
+        It 'skips anything inside folders named "build"' {
+            $copied = Invoke-Rpcp -Param @{
+                RepoPath   = $FixtureRoot
+                ConfigFile = "$FixtureRoot/config.json"
+            }
+
+            $pattern = [regex]::Escape('build/output.txt')
+            $copied | Should -Not -Match $pattern
+        }
+    }
+
+    Context 'ShowCopiedFiles switch' {
+        It 'still copies correctly when -ShowCopiedFiles is used' {
+            $copied = Invoke-Rpcp -Param @{
+                RepoPath        = $FixtureRoot
+                ConfigFile      = "$FixtureRoot/config.json"
+                ShowCopiedFiles = $true
+            }
+
+            $copied | Should -Match 'include\.txt'   # sanity check
+        }
+    }
+}
diff --git a/tests/test_helper/bats-assert b/tests/test_helper/bats-assert
new file mode 160000
index 0000000..b93143a
--- /dev/null
+++ b/tests/test_helper/bats-assert
@@ -0,0 +1 @@
+Subproject commit b93143a1bfbde41d9b7343aab0d36f3ef6549e6b
diff --git a/tests/test_helper/bats-support b/tests/test_helper/bats-support
new file mode 160000
index 0000000..d007fc1
--- /dev/null
+++ b/tests/test_helper/bats-support
@@ -0,0 +1 @@
+Subproject commit d007fc1f451abbad55204fa9c9eb3e6ed5dc5f61