diff --git a/config/services.yml b/config/services.yml
index 618b7c3..7e447ae 100644
--- a/config/services.yml
+++ b/config/services.yml
@@ -7,8 +7,10 @@ services:
         alias: Pcm\IconBundle\Twig\Functions\IconExtension
         public: true
 
+
     Pcm\IconBundle\Twig\Functions\IconExtension:
+        tags: ['twig.extension']
         public: false
         arguments:
-            # $dir:
-                # - '%kernel.project_dir%/public/icons'
+            $directories:
+                - '%kernel.project_dir%/public/icons'
diff --git a/src/Twig/Functions/IconExtension.php b/src/Twig/Functions/IconExtension.php
index fea66b6..0cb5c8e 100644
--- a/src/Twig/Functions/IconExtension.php
+++ b/src/Twig/Functions/IconExtension.php
@@ -4,22 +4,98 @@ declare(strict_types=1);
 
 namespace Pcm\IconBundle\Twig\Functions;
 
+use Exception;
+use InvalidArgumentException;
 use Twig\Extension\AbstractExtension;
 use Twig\TwigFunction;
+use TypeError;
 
 final class IconExtension extends AbstractExtension
 {
+    public function __construct(private array $directories) {}
+
+    private const DEFAULT_OPTIONS = [
+        'icon' => null,
+        'title' => null,
+    ];
+
     /**
      * @inheritDoc
      */
     public function getFunctions(): array
     {
         return [
-            new TwigFunction('icon', [$this, 'render'], [
+            new TwigFunction('icon', [$this, 'renderIcon'], [
                 'is_safe' => ['html']
             ])
         ];
     }
+
+    /**
+     * @param array $options
+     */
+    public function renderIcon(array $userOptions): string
+    {
+        $options = $this->mergeUserOptionsWithDefaults($userOptions);
+
+        $iconFilepath = $this->findSvgFilepath($options['icon']);
+        $rawSvgMarkup = $this->getSvgMarkup($iconFilepath);
+        $cleanSvgMarkup = $this->cleanSvgMarkup($rawSvgMarkup);
+
+        if ($this->titleIsANonEmptyString($options['title'])) {
+            $markup = $this->addTitleToMarkup($cleanSvgMarkup, $options['title']);
+        }
+
+        return $markup;
+    }
+
+    private function mergeUserOptionsWithDefaults(array $userOptions): array
+    {
+        return array_merge(self::DEFAULT_OPTIONS, $userOptions);
+    }
+
+    private function findSvgFilepath(string $iconName): string
+    {
+        foreach ($this->directories as $directory) {
+            $potentialFilepath = sprintf('%s/%s.svg', $directory, $iconName);
+            if (file_exists($potentialFilepath)) {
+                return $potentialFilepath;
+            }
+        }
+
+        throw new IconNotFound(sprintf('File "%s.svg" not found in %s', $iconName, implode(', ', $this->directories)));
+    }
+
+    private function getSvgMarkup(string $filepath): string
+    {
+        return file_get_contents($filepath);
+    }
+
+    private function cleanSvgMarkup(string $markup): string
+    {
+        return preg_replace('/<title>.*<\/title>/', '', $markup);
+    }
+
+    private function titleIsANonEmptyString(mixed $title): bool
+    {
+        if (!is_string($title) && null !== $title)
+            throw new TypeError('Title must be a string!');
+
+
+        if ('' === $title)
+            throw new InvalidArgumentException('Title string must not be empty!');
+
+        return true;
+    }
+
+    private function addTitleToMarkup(string $markup, ?string $title): string
+    {
+        if (null === $title) {
+            return $markup;
+        }
+
+        return preg_replace('/(<svg(.|\n)*?>\n?)/', "$1<title>$title</title>", $markup);
+    }
 }
 
-
+class IconNotFound extends Exception {};
diff --git a/tests/AppKernel.php b/tests/AppKernel.php
new file mode 100644
index 0000000..432fa8b
--- /dev/null
+++ b/tests/AppKernel.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pcm\IconBundle\Tests;
+
+use Pcm\IconBundle\PcmIconBundle;
+use Symfony\Bundle\FrameworkBundle\FrameworkBundle;
+use Symfony\Component\Config\Loader\LoaderInterface;
+use Symfony\Component\HttpKernel\Kernel;
+
+class AppKernel extends Kernel
+{
+    /**
+     * @return array
+     */
+    public function registerBundles(): array
+    {
+        return [
+            new FrameworkBundle(),
+            new PcmIconBundle()
+        ];
+    }
+
+    /**
+     * @param LoaderInterface $loader
+     */
+    public function registerContainerConfiguration(LoaderInterface $loader): void
+    {
+        $loader->load(__DIR__.'/services_'.$this->getEnvironment().'.yml');
+    }
+}
diff --git a/tests/Twig/Functions/IconExtensionTest.php b/tests/Twig/Functions/IconExtensionTest.php
index a45d2fb..50a48d4 100644
--- a/tests/Twig/Functions/IconExtensionTest.php
+++ b/tests/Twig/Functions/IconExtensionTest.php
@@ -4,11 +4,15 @@ declare(strict_types=1);
 
 namespace Pcm\IconBundle\Tests\Twig\Functions;
 
+use Pcm\IconBundle\Tests\AppKernel;
 use Pcm\IconBundle\Twig\Functions\IconExtension;
+use Pcm\IconBundle\Twig\Functions\IconNotFound;
 use PHPUnit\Framework\TestCase;
 
 class IconExtensionTest extends TestCase
 {
+    private const ICON = 'test';
+
     /**
      * @var IconExtension
      */
@@ -16,7 +20,9 @@ class IconExtensionTest extends TestCase
 
     protected function setUp(): void
     {
-        $this->icon = new IconExtension();
+        $kernel = new AppKernel('test', false);
+        $kernel->boot();
+        $this->icon = $kernel->getContainer()->get('pcm_icon.icon_extension');
     }
 
     public function testInstanceOf(): void
@@ -24,4 +30,45 @@ class IconExtensionTest extends TestCase
         $this->assertInstanceOf(IconExtension::class, $this->icon);
     }
 
+    public function testDirectoriesArrayGetsInjected(): void
+    {
+        $reflection = new \ReflectionClass($this->icon);
+        $property = $reflection->getProperty('directories');
+        $directories = $property->getValue($this->icon);
+        $this->assertIsArray($directories);
+        $this->assertCount(1, $directories);
+        $this->assertStringContainsString('tests/icons', $directories[0]);
+    }
+
+    public function testThrowsWhenPassedAnInvalidIconName(): void
+    {
+        $this->expectException(IconNotFound::class);
+        $this->icon->renderIcon(['icon' => random_bytes(8)]);
+    }
+
+    public function testNoTitleExistsIfNotPassedIn(): void
+    {
+        $content = $this->icon->renderIcon(['icon' => self::ICON]);
+        $this->assertStringNotContainsString('<title>', $content);
+        $this->assertStringNotContainsString('</title>', $content);
+    }
+
+    public function testTitleGetsAddedIfSpecified(): void
+    {
+        $title = 'test_title';
+        $content = $this->icon->renderIcon(['icon' => self::ICON, 'title' => $title]);
+        $this->assertMatchesRegularExpression("/<title>{$title}<\/title>/", $content);
+    }
+
+    public function testTitleThrowsIfNotPassedAString(): void
+    {
+        $this->expectException(\TypeError::class);
+        $this->icon->renderIcon(['icon' => self::ICON, 'title' => 99]);
+    }
+
+    public function testTitleThrowsIfPassedAnEmptyString():void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->icon->renderIcon(['icon' => self::ICON, 'title' => '']);
+    }
 }
diff --git a/tests/icons/test.svg b/tests/icons/test.svg
new file mode 100644
index 0000000..2c9ec70
--- /dev/null
+++ b/tests/icons/test.svg
@@ -0,0 +1,5 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="512" height="512" viewBox="96 96 320 320">
+    <title>Some cross lol</title>
+    <line x1="256" y1="112" x2="256" y2="400" style="fill: none; stroke: rgb(0,0, 0); stroke-linecap: round; stroke-linejoin: round; stroke-width: 32px;"></line>
+    <line x1="400" y1="256" x2="112" y2="256" style="fill: none; stroke: #000; stroke-linecap: round; stroke-linejoin: round; stroke-width: 32px;"></line>
+</svg>
diff --git a/tests/services_test.yml b/tests/services_test.yml
new file mode 100644
index 0000000..9a55bfc
--- /dev/null
+++ b/tests/services_test.yml
@@ -0,0 +1,13 @@
+# This config is only here to stop a deprecation notice for Symfony 7
+framework:
+    http_method_override: false
+
+services:
+    pcm_icon.icon_extension:
+        alias: Pcm\IconBundle\Twig\Functions\IconExtension
+        public: true
+
+    Pcm\IconBundle\Twig\Functions\IconExtension:
+        arguments:
+            $directories:
+                - '%kernel.project_dir%/tests/icons'