diff --git a/.gitignore b/.gitignore
index 629afb2..9b96323 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,4 +5,4 @@ composer.lock
 *.swp
 *.swo
 *~
-
+/.phpunit.cache/
\ No newline at end of file
diff --git a/README.md b/README.md
index 4dd4172..dfa4ee5 100644
--- a/README.md
+++ b/README.md
@@ -70,9 +70,12 @@ Some ideas for future classes:
 
 ## Development
 
-This project uses PHP CodeSniffer with PSR-12 standard for code quality.
+This project uses PHP CodeSniffer with PSR-12 standard for code quality and PHPUnit for testing.
 
 ```bash
+# Run tests
+composer test
+
 # Check code style
 composer check
 
@@ -80,6 +83,7 @@ composer check
 composer fix
 
 # Or use vendor binaries directly
+vendor/bin/phpunit
 vendor/bin/phpcs --standard=PSR12 src/
 vendor/bin/phpcbf --standard=PSR12 src/
 ```
diff --git a/composer.json b/composer.json
index 03d8793..f7f8343 100644
--- a/composer.json
+++ b/composer.json
@@ -7,16 +7,23 @@
         "php": "^8.1"
     },
     "require-dev": {
-        "squizlabs/php_codesniffer": "^4.0"
+        "squizlabs/php_codesniffer": "^4.0",
+        "phpunit/phpunit": "^10.0"
     },
     "autoload": {
         "psr-4": {
             "Calvert\\DndErrors\\": "src/"
         }
     },
+    "autoload-dev": {
+        "psr-4": {
+            "Calvert\\DndErrors\\Tests\\": "tests/"
+        }
+    },
     "scripts": {
         "check": "phpcs --standard=PSR12 src/",
-        "fix": "phpcbf --standard=PSR12 src/"
+        "fix": "phpcbf --standard=PSR12 src/",
+        "test": "phpunit"
     },
     "minimum-stability": "stable"
 }
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 0000000..b9b83be
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         colors="true"
+         cacheDirectory=".phpunit.cache"
+         executionOrder="depends,defects"
+         requireCoverageMetadata="false"
+         beStrictAboutCoverageMetadata="true"
+         beStrictAboutOutputDuringTests="true"
+         failOnRisky="true"
+         failOnWarning="true">
+    <testsuites>
+        <testsuite name="default">
+            <directory>tests</directory>
+        </testsuite>
+    </testsuites>
+    <source>
+        <include>
+            <directory suffix=".php">src</directory>
+        </include>
+    </source>
+</phpunit>
+
diff --git a/tests/Archetype/PaladinTest.php b/tests/Archetype/PaladinTest.php
new file mode 100644
index 0000000..ab6f31f
--- /dev/null
+++ b/tests/Archetype/PaladinTest.php
@@ -0,0 +1,93 @@
+<?php
+
+namespace Calvert\DndErrors\Tests\Archetype;
+
+use Calvert\DndErrors\Archetype\Paladin;
+use Calvert\DndErrors\ErrorContext;
+use PHPUnit\Framework\TestCase;
+
+final class PaladinTest extends TestCase
+{
+    private Paladin $paladin;
+
+    protected function setUp(): void
+    {
+        $this->paladin = new Paladin();
+    }
+
+    public function testGetSlugReturnsPaladin(): void
+    {
+        $this->assertSame('paladin', $this->paladin->getSlug());
+    }
+
+    public function testRenderContainsMessage(): void
+    {
+        $context = new ErrorContext(
+            type: 'Error',
+            message: 'Test error message',
+            file: '/path/to/file.php',
+            line: 42
+        );
+
+        $output = $this->paladin->render($context);
+
+        $this->assertStringContainsString('Test error message', $output);
+        $this->assertStringContainsString('/path/to/file.php:42', $output);
+    }
+
+    public function testRenderContainsPaladinEmoji(): void
+    {
+        $context = new ErrorContext(
+            type: 'Error',
+            message: 'Test error',
+        );
+
+        $output = $this->paladin->render($context);
+
+        // Should contain paladin emoji (✨ or ⚔️)
+        $this->assertTrue(
+            str_contains($output, '✨') || str_contains($output, '⚔️'),
+            'Output should contain paladin emoji'
+        );
+    }
+
+    public function testRenderIncludesLocationWhenProvided(): void
+    {
+        $context = new ErrorContext(
+            type: 'Error',
+            message: 'Test error',
+            file: 'test.php',
+            line: 10
+        );
+
+        $output = $this->paladin->render($context);
+
+        $this->assertStringContainsString('test.php:10', $output);
+    }
+
+    public function testRenderShowsUnknownLocationWhenFileOrLineMissing(): void
+    {
+        $context = new ErrorContext(
+            type: 'Error',
+            message: 'Test error',
+        );
+
+        $output = $this->paladin->render($context);
+
+        $this->assertStringContainsString('Unknown location', $output);
+    }
+
+    public function testRenderForFatalError(): void
+    {
+        $context = new ErrorContext(
+            type: 'fatal',
+            message: 'Fatal error occurred',
+        );
+
+        $output = $this->paladin->render($context);
+
+        // Fatal errors should have special headers
+        $this->assertStringContainsString('Fatal error occurred', $output);
+    }
+}
+
diff --git a/tests/Archetype/RangerTest.php b/tests/Archetype/RangerTest.php
new file mode 100644
index 0000000..39954fc
--- /dev/null
+++ b/tests/Archetype/RangerTest.php
@@ -0,0 +1,51 @@
+<?php
+
+namespace Calvert\DndErrors\Tests\Archetype;
+
+use Calvert\DndErrors\Archetype\Ranger;
+use Calvert\DndErrors\ErrorContext;
+use PHPUnit\Framework\TestCase;
+
+final class RangerTest extends TestCase
+{
+    private Ranger $ranger;
+
+    protected function setUp(): void
+    {
+        $this->ranger = new Ranger();
+    }
+
+    public function testGetSlugReturnsRanger(): void
+    {
+        $this->assertSame('ranger', $this->ranger->getSlug());
+    }
+
+    public function testRenderContainsMessage(): void
+    {
+        $context = new ErrorContext(
+            type: 'Error',
+            message: 'Trail lost',
+            file: '/forest/path.php',
+            line: 15
+        );
+
+        $output = $this->ranger->render($context);
+
+        $this->assertStringContainsString('Trail lost', $output);
+        $this->assertStringContainsString('/forest/path.php:15', $output);
+    }
+
+    public function testRenderContainsRangerEmoji(): void
+    {
+        $context = new ErrorContext(
+            type: 'Error',
+            message: 'Test error',
+        );
+
+        $output = $this->ranger->render($context);
+
+        // Should contain ranger emoji 🏹
+        $this->assertStringContainsString('🏹', $output);
+    }
+}
+
diff --git a/tests/Archetype/WizardTest.php b/tests/Archetype/WizardTest.php
new file mode 100644
index 0000000..bdf4ff0
--- /dev/null
+++ b/tests/Archetype/WizardTest.php
@@ -0,0 +1,51 @@
+<?php
+
+namespace Calvert\DndErrors\Tests\Archetype;
+
+use Calvert\DndErrors\Archetype\Wizard;
+use Calvert\DndErrors\ErrorContext;
+use PHPUnit\Framework\TestCase;
+
+final class WizardTest extends TestCase
+{
+    private Wizard $wizard;
+
+    protected function setUp(): void
+    {
+        $this->wizard = new Wizard();
+    }
+
+    public function testGetSlugReturnsWizard(): void
+    {
+        $this->assertSame('wizard', $this->wizard->getSlug());
+    }
+
+    public function testRenderContainsMessage(): void
+    {
+        $context = new ErrorContext(
+            type: 'Error',
+            message: 'Arcane failure',
+            file: '/spellbook/incantation.php',
+            line: 7
+        );
+
+        $output = $this->wizard->render($context);
+
+        $this->assertStringContainsString('Arcane failure', $output);
+        $this->assertStringContainsString('/spellbook/incantation.php:7', $output);
+    }
+
+    public function testRenderContainsWizardEmoji(): void
+    {
+        $context = new ErrorContext(
+            type: 'Error',
+            message: 'Test error',
+        );
+
+        $output = $this->wizard->render($context);
+
+        // Should contain wizard emoji 🧙
+        $this->assertStringContainsString('🧙', $output);
+    }
+}
+
diff --git a/tests/ErrorContextTest.php b/tests/ErrorContextTest.php
new file mode 100644
index 0000000..e1b7a42
--- /dev/null
+++ b/tests/ErrorContextTest.php
@@ -0,0 +1,44 @@
+<?php
+
+namespace Calvert\DndErrors\Tests;
+
+use Calvert\DndErrors\ErrorContext;
+use PHPUnit\Framework\TestCase;
+
+final class ErrorContextTest extends TestCase
+{
+    public function testCanCreateErrorContextWithAllProperties(): void
+    {
+        $context = new ErrorContext(
+            type: 'RuntimeException',
+            message: 'Test error message',
+            file: '/path/to/file.php',
+            line: 42,
+            trace: array('trace' => 'data'),
+            phpVersion: '8.1.0'
+        );
+
+        $this->assertSame('RuntimeException', $context->type);
+        $this->assertSame('Test error message', $context->message);
+        $this->assertSame('/path/to/file.php', $context->file);
+        $this->assertSame(42, $context->line);
+        $this->assertSame(array('trace' => 'data'), $context->trace);
+        $this->assertSame('8.1.0', $context->phpVersion);
+    }
+
+    public function testCanCreateErrorContextWithMinimalProperties(): void
+    {
+        $context = new ErrorContext(
+            type: 'Error',
+            message: 'Test message'
+        );
+
+        $this->assertSame('Error', $context->type);
+        $this->assertSame('Test message', $context->message);
+        $this->assertNull($context->file);
+        $this->assertNull($context->line);
+        $this->assertSame(array(), $context->trace);
+        $this->assertNull($context->phpVersion);
+    }
+}
+