diff --git a/tests/expectations/source.txt b/tests/expectations/source.txt
new file mode 100644
index 0000000..2272678
--- /dev/null
+++ b/tests/expectations/source.txt
@@ -0,0 +1,7 @@
+  1      <?php declare(strict_types=1);
+  2      function f()
+  3      {
+- 4          $result = 'result';
+  5      
+  6          return $result;
+- 7      }
diff --git a/tests/unit/FileRendererTest.php b/tests/unit/FileRendererTest.php
new file mode 100644
index 0000000..97ca2fb
--- /dev/null
+++ b/tests/unit/FileRendererTest.php
@@ -0,0 +1,38 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of FOAL.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace SebastianBergmann\FOAL;
+
+use function file;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Small;
+use PHPUnit\Framework\Attributes\UsesClass;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(FileRenderer::class)]
+#[UsesClass(File::class)]
+#[Small]
+final class FileRendererTest extends TestCase
+{
+    public function testRendersFileAsString(): void
+    {
+        $this->assertStringEqualsFile(
+            __DIR__ . '/../expectations/source.txt',
+            (new FileRenderer)->render($this->file()),
+        );
+    }
+
+    private function file(): File
+    {
+        return new File(
+            file(__DIR__ . '/../fixture/source.php'),
+            [4, 7],
+        );
+    }
+}
diff --git a/tests/unit/FileTest.php b/tests/unit/FileTest.php
new file mode 100644
index 0000000..d6b28d4
--- /dev/null
+++ b/tests/unit/FileTest.php
@@ -0,0 +1,44 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of FOAL.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace SebastianBergmann\FOAL;
+
+use function file;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Small;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(File::class)]
+#[Small]
+final class FileTest extends TestCase
+{
+    public function testHasSourceLines(): void
+    {
+        $this->assertSame(
+            file(__DIR__ . '/../fixture/source.php'),
+            $this->file()->sourceLines(),
+        );
+    }
+
+    public function testLinesEliminatedByOptimizer(): void
+    {
+        $this->assertSame(
+            [4, 7],
+            $this->file()->linesEliminatedByOptimizer(),
+        );
+    }
+
+    private function file(): File
+    {
+        return new File(
+            file(__DIR__ . '/../fixture/source.php'),
+            [4, 7],
+        );
+    }
+}