diff --git a/src/Tracer/ErrorHandler.php b/src/Tracer/ErrorHandler.php
index 08fdf590f..82bf92874 100644
--- a/src/Tracer/ErrorHandler.php
+++ b/src/Tracer/ErrorHandler.php
@@ -16,19 +16,16 @@
 
 namespace Quantum\Tracer;
 
-use Quantum\Storage\Contracts\LocalFilesystemAdapterInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 use Symfony\Component\Console\Output\ConsoleOutput;
 use Quantum\Renderer\Exceptions\RendererException;
 use Quantum\Config\Exceptions\ConfigException;
 use Quantum\App\Exceptions\BaseException;
-use Quantum\View\Factories\ViewFactory;
 use Quantum\Di\Exceptions\DiException;
+use Quantum\Http\Enums\StatusCode;
 use Quantum\Logger\Logger;
 use ReflectionException;
-use Psr\Log\LogLevel;
 use ErrorException;
-use ParseError;
 use Throwable;
 use Exception;
 
@@ -38,32 +35,20 @@
  */
 class ErrorHandler
 {
-    /**
-     * Number of lines to be returned
-     */
-    public const NUM_LINES = 10;
-
-    /**
-     * @var array<int, string>
-     */
-    public const ERROR_TYPES = [
-        E_ERROR => 'error',
-        E_WARNING => 'warning',
-        E_PARSE => 'error',
-        E_NOTICE => 'notice',
-        E_CORE_ERROR => 'error',
-        E_CORE_WARNING => 'warning',
-        E_COMPILE_ERROR => 'error',
-        E_COMPILE_WARNING => 'warning',
-        E_USER_ERROR => 'error',
-        E_USER_WARNING => 'warning',
-        E_USER_NOTICE => 'notice',
-        E_STRICT => 'notice',
-        E_RECOVERABLE_ERROR => 'error',
-    ];
-
     private ?Logger $logger = null;
     private ?OutputInterface $cliOutput = null;
+    private ExceptionSeverityResolver $severityResolver;
+    private WebExceptionRenderer $webExceptionRenderer;
+
+    public function __construct(
+        ?ExceptionSeverityResolver $severityResolver = null,
+        ?StackTraceFormatter $stackTraceFormatter = null,
+        ?WebExceptionRenderer $webExceptionRenderer = null
+    ) {
+        $this->severityResolver = $severityResolver ?? new ExceptionSeverityResolver();
+        $formatter = $stackTraceFormatter ?? new StackTraceFormatter();
+        $this->webExceptionRenderer = $webExceptionRenderer ?? new WebExceptionRenderer($formatter);
+    }
 
     private function __clone()
     {
@@ -110,30 +95,36 @@ public function handleException(Throwable $throwable): void
     private function handleCliException(Throwable $throwable): void
     {
         $output = $this->cliOutput ?? new ConsoleOutput();
-        $output->writeln('<error>' . $throwable->getMessage() . '</error>');
+
+        if (!is_debug_mode()) {
+            $output->writeln('<error>' . $throwable->getMessage() . '</error>');
+            return;
+        }
+
+        $output->writeln('<error>' . get_class($throwable) . ': ' . $throwable->getMessage() . '</error>');
+        $output->writeln('In ' . $throwable->getFile() . ':' . $throwable->getLine());
+        $output->writeln($throwable->getTraceAsString());
     }
 
     /**
-     * @throws ConfigException|RendererException|DiException|BaseException|ReflectionException|Exception
+     * @throws DiException|BaseException|ReflectionException|Exception
      */
     private function handleWebException(Throwable $throwable): void
     {
-        $view = ViewFactory::get();
         $errorType = $this->getErrorType($throwable);
 
-        if (is_debug_mode()) {
-            $errorPage = $view->renderPartial('errors' . DS . 'trace', [
-                'stackTrace' => $this->composeStackTrace($throwable),
-                'errorMessage' => $throwable->getMessage(),
-                'severity' => ucfirst($errorType),
-            ]);
-        } else {
-            $errorPage = $view->renderPartial('errors' . DS . '500');
+        if (!is_debug_mode()) {
             $this->logError($throwable, $errorType);
         }
 
-        response()->html($errorPage);
-        response()->send();
+        try {
+            $errorPage = $this->webExceptionRenderer->render($throwable, $errorType);
+            response()->html($errorPage, StatusCode::INTERNAL_SERVER_ERROR);
+            response()->send();
+        } catch (Throwable $e) {
+            response()->html('Internal Server Error', StatusCode::INTERNAL_SERVER_ERROR);
+            response()->send();
+        }
     }
 
     private function logError(Throwable $e, string $errorType): void
@@ -147,95 +138,11 @@ private function logError(Throwable $e, string $errorType): void
         $this->logger->$logMethod($e->getMessage(), ['trace' => $e->getTraceAsString()]);
     }
 
-    /**
-     * Composes the stack trace
-     * @return array<int, array{file: string, code: string}>
-     * @throws ConfigException|RendererException|DiException|BaseException|ReflectionException
-     */
-    private function composeStackTrace(Throwable $e): array
-    {
-        $trace[] = [
-            'file' => $e->getFile(),
-            'code' => $this->getSourceCode($e->getFile(), $e->getLine(), 'error-line'),
-        ];
-
-        foreach ($e->getTrace() as $item) {
-            if (($item['class'] ?? null) === self::class) {
-                continue;
-            }
-
-            if (isset($item['file'])) {
-                $trace[] = [
-                    'file' => $item['file'],
-                    'code' => $this->getSourceCode($item['file'], $item['line'] ?? 1, 'switch-line'),
-                ];
-            }
-        }
-
-        return $trace;
-    }
-
-    /**
-     * Gets the source code where the error happens
-     * @throws ConfigException|RendererException|DiException|BaseException|ReflectionException
-     */
-    private function getSourceCode(string $filename, int $lineNumber, string $className): string
-    {
-        $lineNumber--;
-
-        $halfLines = intdiv(self::NUM_LINES, 2);
-        $start = max($lineNumber - $halfLines, 1);
-
-        $adapter = fs()->getAdapter();
-
-        if (!$adapter instanceof LocalFilesystemAdapterInterface) {
-            return '';
-        }
-
-        $lines = $adapter->getLines($filename, $start, self::NUM_LINES);
-
-        $code = '<ol start="' . key($lines) . '">';
-
-        foreach ($lines as $currentLineNumber => $line) {
-            $code .= $this->formatLineItem($currentLineNumber, $line, $lineNumber, $className);
-        }
-
-        return $code . '</ol>';
-    }
-
-    /**
-     * Formats the line item
-     */
-    private function formatLineItem(int $currentLineNumber, string $line, int $lineNumber, string $className): string
-    {
-        $highlightClass = $currentLineNumber === $lineNumber ? " class=\"{$className}\"" : '';
-
-        $encodedLine = htmlspecialchars($line, ENT_QUOTES);
-
-        return sprintf(
-            '<li%s><pre>%s</pre></li>',
-            $highlightClass,
-            $encodedLine
-        );
-    }
-
     /**
      * Gets the error type based on the exception class
      */
     private function getErrorType(Throwable $e): string
     {
-        if ($e instanceof ErrorException) {
-            return self::ERROR_TYPES[$e->getSeverity()] ?? LogLevel::ERROR;
-        }
-
-        if ($e instanceof ParseError) {
-            return LogLevel::CRITICAL;
-        }
-
-        if ($e instanceof ReflectionException) {
-            return LogLevel::WARNING;
-        }
-
-        return LogLevel::ERROR;
+        return $this->severityResolver->resolve($e);
     }
 }
diff --git a/src/Tracer/ExceptionSeverityResolver.php b/src/Tracer/ExceptionSeverityResolver.php
new file mode 100644
index 000000000..1090272b0
--- /dev/null
+++ b/src/Tracer/ExceptionSeverityResolver.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Quantum PHP Framework
+ *
+ * An open source software development framework for PHP
+ *
+ * @package Quantum
+ * @author Arman Ag. <arman.ag@softberg.org>
+ * @copyright Copyright (c) 2018 Softberg LLC (https://softberg.org)
+ * @link http://quantum.softberg.org/
+ * @since 3.0.0
+ */
+
+namespace Quantum\Tracer;
+
+use ReflectionException;
+use Psr\Log\LogLevel;
+use ErrorException;
+use ParseError;
+use Throwable;
+
+final class ExceptionSeverityResolver
+{
+    /**
+     * @var array<int, string>
+     */
+    private const ERROR_TYPES = [
+        E_ERROR => 'error',
+        E_WARNING => 'warning',
+        E_PARSE => 'error',
+        E_NOTICE => 'notice',
+        E_CORE_ERROR => 'error',
+        E_CORE_WARNING => 'warning',
+        E_COMPILE_ERROR => 'error',
+        E_COMPILE_WARNING => 'warning',
+        E_USER_ERROR => 'error',
+        E_USER_WARNING => 'warning',
+        E_USER_NOTICE => 'notice',
+        E_STRICT => 'notice',
+        E_RECOVERABLE_ERROR => 'error',
+    ];
+
+    public function resolve(Throwable $throwable): string
+    {
+        if ($throwable instanceof ErrorException) {
+            return self::ERROR_TYPES[$throwable->getSeverity()] ?? LogLevel::ERROR;
+        }
+
+        if ($throwable instanceof ParseError) {
+            return LogLevel::CRITICAL;
+        }
+
+        if ($throwable instanceof ReflectionException) {
+            return LogLevel::WARNING;
+        }
+
+        return LogLevel::ERROR;
+    }
+}
diff --git a/src/Tracer/StackTraceFormatter.php b/src/Tracer/StackTraceFormatter.php
new file mode 100644
index 000000000..e142e17c1
--- /dev/null
+++ b/src/Tracer/StackTraceFormatter.php
@@ -0,0 +1,83 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Quantum PHP Framework
+ *
+ * An open source software development framework for PHP
+ *
+ * @package Quantum
+ * @author Arman Ag. <arman.ag@softberg.org>
+ * @copyright Copyright (c) 2018 Softberg LLC (https://softberg.org)
+ * @link http://quantum.softberg.org/
+ * @since 3.0.0
+ */
+
+namespace Quantum\Tracer;
+
+use Quantum\Storage\Contracts\LocalFilesystemAdapterInterface;
+use Throwable;
+
+final class StackTraceFormatter
+{
+    private const NUM_LINES = 10;
+
+    /**
+     * @return array<int, array{file: string, code: string}>
+     */
+    public function compose(Throwable $throwable): array
+    {
+        $trace[] = [
+            'file' => $throwable->getFile(),
+            'code' => $this->getSourceCode($throwable->getFile(), $throwable->getLine(), 'error-line'),
+        ];
+
+        foreach ($throwable->getTrace() as $item) {
+            if (($item['class'] ?? null) === ErrorHandler::class) {
+                continue;
+            }
+
+            if (isset($item['file'])) {
+                $trace[] = [
+                    'file' => $item['file'],
+                    'code' => $this->getSourceCode($item['file'], $item['line'] ?? 1, 'switch-line'),
+                ];
+            }
+        }
+
+        return $trace;
+    }
+
+    public function getSourceCode(string $filename, int $lineNumber, string $className): string
+    {
+        $lineNumber--;
+
+        $halfLines = intdiv(self::NUM_LINES, 2);
+        $start = max($lineNumber - $halfLines, 1);
+
+        $adapter = fs()->getAdapter();
+
+        if (!$adapter instanceof LocalFilesystemAdapterInterface) {
+            return '';
+        }
+
+        $lines = $adapter->getLines($filename, $start, self::NUM_LINES);
+
+        $code = '<ol start="' . key($lines) . '">';
+
+        foreach ($lines as $currentLineNumber => $line) {
+            $code .= $this->formatLineItem($currentLineNumber, $line, $lineNumber, $className);
+        }
+
+        return $code . '</ol>';
+    }
+
+    public function formatLineItem(int $currentLineNumber, string $line, int $lineNumber, string $className): string
+    {
+        $highlightClass = $currentLineNumber === $lineNumber ? " class=\"{$className}\"" : '';
+        $encodedLine = htmlspecialchars($line, ENT_QUOTES);
+
+        return sprintf('<li%s><pre>%s</pre></li>', $highlightClass, $encodedLine);
+    }
+}
diff --git a/src/Tracer/WebExceptionRenderer.php b/src/Tracer/WebExceptionRenderer.php
new file mode 100644
index 000000000..e04f2c026
--- /dev/null
+++ b/src/Tracer/WebExceptionRenderer.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Quantum PHP Framework
+ *
+ * An open source software development framework for PHP
+ *
+ * @package Quantum
+ * @author Arman Ag. <arman.ag@softberg.org>
+ * @copyright Copyright (c) 2018 Softberg LLC (https://softberg.org)
+ * @link http://quantum.softberg.org/
+ * @since 3.0.0
+ */
+
+namespace Quantum\Tracer;
+
+use Quantum\Renderer\Exceptions\RendererException;
+use Quantum\Config\Exceptions\ConfigException;
+use Quantum\App\Exceptions\BaseException;
+use Quantum\Di\Exceptions\DiException;
+use ReflectionException;
+use Throwable;
+
+class WebExceptionRenderer
+{
+    private StackTraceFormatter $stackTraceFormatter;
+
+    public function __construct(?StackTraceFormatter $stackTraceFormatter = null)
+    {
+        $this->stackTraceFormatter = $stackTraceFormatter ?? new StackTraceFormatter();
+    }
+
+    /**
+     * @throws ConfigException|RendererException|DiException|BaseException|ReflectionException
+     */
+    public function render(Throwable $throwable, string $errorType): string
+    {
+        if (is_debug_mode()) {
+            return view()->renderPartial('errors' . DS . 'trace', [
+                'stackTrace' => $this->stackTraceFormatter->compose($throwable),
+                'errorMessage' => $throwable->getMessage(),
+                'severity' => ucfirst($errorType),
+            ]);
+        }
+
+        return view()->renderPartial('errors' . DS . '500');
+    }
+}
diff --git a/tests/Unit/AppTestCase.php b/tests/Unit/AppTestCase.php
index 0d4cc8201..40f9f4b61 100644
--- a/tests/Unit/AppTestCase.php
+++ b/tests/Unit/AppTestCase.php
@@ -15,6 +15,7 @@
 use Quantum\Router\Route;
 use Quantum\Http\Response;
 use ReflectionClass;
+use ReflectionMethod;
 use Quantum\App\App;
 use Quantum\Di\Di;
 use ReflectionProperty;
@@ -92,6 +93,14 @@ protected function getPrivateProperty($object, $property)
         return $property->getValue($object);
     }
 
+    protected function invokePrivateMethod(object $object, string $method, array $args = [])
+    {
+        $reflectionMethod = new ReflectionMethod($object, $method);
+        $reflectionMethod->setAccessible(true);
+
+        return $reflectionMethod->invokeArgs($object, $args);
+    }
+
     protected function createFile(string $filePath, string $content)
     {
         $this->fs->put($filePath, $content);
diff --git a/tests/Unit/Tracer/ErrorHandlerTest.php b/tests/Unit/Tracer/ErrorHandlerTest.php
index bd03fe966..3c12df59a 100644
--- a/tests/Unit/Tracer/ErrorHandlerTest.php
+++ b/tests/Unit/Tracer/ErrorHandlerTest.php
@@ -2,16 +2,12 @@
 
 namespace Quantum\Tests\Unit\Tracer;
 
-use Quantum\Storage\Factories\FileSystemFactory;
-use Quantum\Storage\Contracts\FilesystemAdapterInterface;
-use Quantum\Storage\FileSystem;
+use Symfony\Component\Console\Output\BufferedOutput;
+use Quantum\Tracer\WebExceptionRenderer;
 use Quantum\Tests\Unit\AppTestCase;
 use Quantum\Tracer\ErrorHandler;
-use Quantum\Di\Di;
 use Quantum\Logger\Logger;
-use Symfony\Component\Console\Output\BufferedOutput;
 use ReflectionException;
-use ReflectionMethod;
 use ErrorException;
 use ParseError;
 use Exception;
@@ -94,16 +90,10 @@ public function testHandleErrorReturnsFalseForSuppressedErrors(): void
         }
     }
 
-    public function testErrorTypesConstant(): void
-    {
-        $this->assertEquals('error', ErrorHandler::ERROR_TYPES[E_ERROR]);
-        $this->assertEquals('warning', ErrorHandler::ERROR_TYPES[E_WARNING]);
-        $this->assertEquals('notice', ErrorHandler::ERROR_TYPES[E_NOTICE]);
-        $this->assertEquals('error', ErrorHandler::ERROR_TYPES[E_PARSE]);
-    }
-
     public function testHandleExceptionCliWritesExceptionMessage(): void
     {
+        config()->set('app.debug', false);
+
         $output = new BufferedOutput();
         $this->errorHandler->setCliOutput($output);
 
@@ -112,6 +102,21 @@ public function testHandleExceptionCliWritesExceptionMessage(): void
         $this->assertStringContainsString('CLI failure', $output->fetch());
     }
 
+    public function testHandleExceptionCliInDebugModeWritesVerboseDiagnostics(): void
+    {
+        config()->set('app.debug', true);
+
+        $output = new BufferedOutput();
+        $this->errorHandler->setCliOutput($output);
+
+        $this->errorHandler->handleException(new Exception('CLI debug failure'));
+
+        $display = $output->fetch();
+        $this->assertStringContainsString(Exception::class . ': CLI debug failure', $display);
+        $this->assertStringContainsString('In ', $display);
+        $this->assertStringContainsString(__FILE__, $display);
+    }
+
     public function testHandleWebExceptionInDebugModeRendersTraceView(): void
     {
         config()->set('app.debug', true);
@@ -119,7 +124,7 @@ public function testHandleWebExceptionInDebugModeRendersTraceView(): void
         $exception = new Exception('Web debug failure');
 
         ob_start();
-        $this->invokePrivateMethod('handleWebException', [$exception]);
+        $this->invokePrivateMethod($this->errorHandler, 'handleWebException', [$exception]);
         ob_get_clean();
 
         $content = response()->getContent();
@@ -143,18 +148,38 @@ public function testHandleWebExceptionInProductionModeLogsAndRenders500(): void
         $exception = new ErrorException('Web production warning', 0, E_WARNING, __FILE__, __LINE__);
 
         ob_start();
-        $this->invokePrivateMethod('handleWebException', [$exception]);
+        $this->invokePrivateMethod($this->errorHandler, 'handleWebException', [$exception]);
         ob_get_clean();
 
         $content = response()->getContent();
         $this->assertStringContainsString('ERROR 500 VIEW', $content);
     }
 
+    public function testHandleWebExceptionFallsBackWhenRendererThrows(): void
+    {
+        config()->set('app.debug', true);
+
+        $renderer = Mockery::mock(WebExceptionRenderer::class);
+        $renderer->shouldReceive('render')
+            ->once()
+            ->andThrow(new Exception('render failed'));
+
+        $handler = new ErrorHandler(null, null, $renderer);
+
+        ob_start();
+        $this->invokePrivateMethod($handler, 'handleWebException', [new Exception('boom')]);
+        ob_get_clean();
+
+        $this->assertSame('Internal Server Error', response()->getContent());
+        $this->assertSame(500, response()->getStatusCode());
+        $this->assertStringStartsWith('text/html', (string) response()->getHeader('Content-Type'));
+    }
+
     public function testLogErrorReturnsEarlyWhenLoggerIsNull(): void
     {
         $this->setPrivateProperty($this->errorHandler, 'logger', null);
 
-        $this->invokePrivateMethod('logError', [new Exception('No logger'), 'error']);
+        $this->invokePrivateMethod($this->errorHandler, 'logError', [new Exception('No logger'), 'error']);
 
         $this->assertTrue(true);
     }
@@ -168,156 +193,17 @@ public function testLogErrorFallsBackToErrorMethodForUnknownLevel(): void
 
         $this->setPrivateProperty($this->errorHandler, 'logger', $logger);
 
-        $this->invokePrivateMethod('logError', [new Exception('Unknown level message'), 'not_existing_level']);
+        $this->invokePrivateMethod($this->errorHandler, 'logError', [new Exception('Unknown level message'), 'not_existing_level']);
 
         $this->assertTrue(true);
     }
 
-    public function testComposeStackTraceSkipsHandlerClassEntriesAndBuildsCodeSnippets(): void
-    {
-        $sourceFile = PROJECT_ROOT . DS . 'shared' . DS . 'trace-source.php';
-        $this->createFile($sourceFile, "<?php\nline1\nline2\nline3\nline4\nline5\n");
-
-        try {
-            $throwable = new Exception('trace');
-            $throwableProperty = new \ReflectionProperty(Exception::class, 'file');
-            $throwableProperty->setAccessible(true);
-            $throwableProperty->setValue($throwable, $sourceFile);
-
-            $lineProperty = new \ReflectionProperty(Exception::class, 'line');
-            $lineProperty->setAccessible(true);
-            $lineProperty->setValue($throwable, 3);
-
-            $traceProperty = new \ReflectionProperty(Exception::class, 'trace');
-            $traceProperty->setAccessible(true);
-            $traceProperty->setValue($throwable, [
-                ['class' => ErrorHandler::class, 'file' => $sourceFile, 'line' => 2],
-                ['class' => 'ExternalClass', 'file' => $sourceFile, 'line' => 4],
-                ['class' => 'NoFileClass'],
-            ]);
-
-            $trace = $this->invokePrivateMethod('composeStackTrace', [$throwable]);
-
-            $this->assertCount(2, $trace);
-            $this->assertSame($sourceFile, $trace[0]['file']);
-            $this->assertStringContainsString('<ol start="1">', $trace[0]['code']);
-            $this->assertStringContainsString('class="error-line"', $trace[0]['code']);
-            $this->assertSame($sourceFile, $trace[1]['file']);
-            $this->assertStringContainsString('class="switch-line"', $trace[1]['code']);
-        } finally {
-            $this->removeFile($sourceFile);
-        }
-    }
-
-    public function testGetSourceCodeReturnsEmptyStringForNonLocalAdapter(): void
-    {
-        $adapter = new class () implements FilesystemAdapterInterface {
-            public function makeDirectory(string $dirname, ?string $parentId = null): bool
-            {
-                return false;
-            }
-            public function removeDirectory(string $dirname): bool
-            {
-                return false;
-            }
-            public function get(string $filename)
-            {
-                return false;
-            }
-            public function put(string $filename, $content, ?string $parentId = null)
-            {
-                return false;
-            }
-            public function append(string $filename, $content)
-            {
-                return false;
-            }
-            public function rename(string $oldName, string $newName): bool
-            {
-                return false;
-            }
-            public function copy(string $source, string $dest): bool
-            {
-                return false;
-            }
-            public function exists(string $filename): bool
-            {
-                return false;
-            }
-            public function size(string $filename)
-            {
-                return false;
-            }
-            public function lastModified(string $filename)
-            {
-                return false;
-            }
-            public function remove(string $filename): bool
-            {
-                return false;
-            }
-            public function isFile(string $filename): bool
-            {
-                return false;
-            }
-            public function isDirectory(string $dirname): bool
-            {
-                return false;
-            }
-            public function listDirectory(string $dirname)
-            {
-                return false;
-            }
-        };
-
-        $factory = Di::get(FileSystemFactory::class);
-        $instancesProperty = new \ReflectionProperty(FileSystemFactory::class, 'instances');
-        $instancesProperty->setAccessible(true);
-        $originalInstances = $instancesProperty->getValue($factory);
-
-        try {
-            $instancesProperty->setValue($factory, ['local' => new FileSystem($adapter)]);
-
-            $code = $this->invokePrivateMethod('getSourceCode', [__FILE__, 10, 'error-line']);
-
-            $this->assertSame('', $code);
-        } finally {
-            $instancesProperty->setValue($factory, $originalInstances);
-        }
-    }
-
-    public function testGetSourceCodeBuildsOrderedListForLocalAdapter(): void
-    {
-        $file = PROJECT_ROOT . DS . 'shared' . DS . 'source-code.php';
-        $this->createFile($file, "<?php\nA\nB\nC\nD\nE\nF\nG\n");
-
-        try {
-            $code = $this->invokePrivateMethod('getSourceCode', [$file, 5, 'error-line']);
-
-            $this->assertStringContainsString('<ol start="1">', $code);
-            $this->assertStringContainsString('class="error-line"', $code);
-            $this->assertStringContainsString('<pre>C</pre>', $code);
-        } finally {
-            $this->removeFile($file);
-        }
-    }
-
-    public function testFormatLineItemEscapesHtmlAndAppliesHighlightClass(): void
-    {
-        $html = $this->invokePrivateMethod('formatLineItem', [5, '<div class="x">A&B</div>', 5, 'switch-line']);
-        $plain = $this->invokePrivateMethod('formatLineItem', [4, 'plain', 5, 'switch-line']);
-
-        $this->assertStringContainsString('class="switch-line"', $html);
-        $this->assertStringContainsString('&lt;div class=&quot;x&quot;&gt;A&amp;B&lt;/div&gt;', $html);
-        $this->assertStringNotContainsString('class="switch-line"', $plain);
-    }
-
     /**
      * @dataProvider errorTypeProvider
      */
     public function testGetErrorTypeMappings(\Throwable $throwable, string $expected): void
     {
-        $type = $this->invokePrivateMethod('getErrorType', [$throwable]);
+        $type = $this->invokePrivateMethod($this->errorHandler, 'getErrorType', [$throwable]);
 
         $this->assertSame($expected, $type);
     }
@@ -336,15 +222,4 @@ public function errorTypeProvider(): array
         ];
     }
 
-    /**
-     * @param array<int, mixed> $args
-     * @return mixed
-     */
-    private function invokePrivateMethod(string $method, array $args = [])
-    {
-        $reflectionMethod = new ReflectionMethod($this->errorHandler, $method);
-        $reflectionMethod->setAccessible(true);
-
-        return $reflectionMethod->invokeArgs($this->errorHandler, $args);
-    }
 }
diff --git a/tests/Unit/Tracer/ExceptionSeverityResolverTest.php b/tests/Unit/Tracer/ExceptionSeverityResolverTest.php
new file mode 100644
index 000000000..c60981885
--- /dev/null
+++ b/tests/Unit/Tracer/ExceptionSeverityResolverTest.php
@@ -0,0 +1,42 @@
+<?php
+
+namespace Quantum\Tests\Unit\Tracer;
+
+use Quantum\Tracer\ExceptionSeverityResolver;
+use PHPUnit\Framework\TestCase;
+use ReflectionException;
+use ErrorException;
+use ParseError;
+use Exception;
+
+class ExceptionSeverityResolverTest extends TestCase
+{
+    private ExceptionSeverityResolver $resolver;
+
+    public function setUp(): void
+    {
+        $this->resolver = new ExceptionSeverityResolver();
+    }
+
+    /**
+     * @dataProvider mappingProvider
+     */
+    public function testResolveMappings(\Throwable $throwable, string $expected): void
+    {
+        $this->assertSame($expected, $this->resolver->resolve($throwable));
+    }
+
+    /**
+     * @return array<string, array{0: \Throwable, 1: string}>
+     */
+    public function mappingProvider(): array
+    {
+        return [
+            'mapped-error-exception' => [new ErrorException('x', 0, E_WARNING), 'warning'],
+            'unmapped-error-exception' => [new ErrorException('x', 0, E_USER_DEPRECATED), 'error'],
+            'parse-error' => [new ParseError('bad syntax'), 'critical'],
+            'reflection-exception' => [new ReflectionException('reflection failed'), 'warning'],
+            'generic-exception' => [new Exception('unknown'), 'error'],
+        ];
+    }
+}
diff --git a/tests/Unit/Tracer/StackTraceFormatterTest.php b/tests/Unit/Tracer/StackTraceFormatterTest.php
new file mode 100644
index 000000000..4b6af87f5
--- /dev/null
+++ b/tests/Unit/Tracer/StackTraceFormatterTest.php
@@ -0,0 +1,74 @@
+<?php
+
+namespace Quantum\Tests\Unit\Tracer;
+
+use Quantum\Storage\Contracts\FilesystemAdapterInterface;
+use Quantum\Storage\Factories\FileSystemFactory;
+use Quantum\Tracer\StackTraceFormatter;
+use Quantum\Tests\Unit\AppTestCase;
+use Quantum\Tracer\ErrorHandler;
+use Quantum\Storage\FileSystem;
+use ReflectionProperty;
+use Quantum\Di\Di;
+use Exception;
+use Mockery;
+
+class StackTraceFormatterTest extends AppTestCase
+{
+    private StackTraceFormatter $formatter;
+
+    public function setUp(): void
+    {
+        parent::setUp();
+
+        $this->formatter = new StackTraceFormatter();
+    }
+
+    public function testComposeSkipsErrorHandlerClassEntriesAndBuildsCodeSnippets(): void
+    {
+        $sourceFile = PROJECT_ROOT . DS . 'shared' . DS . 'trace-source-formatter.php';
+        $this->createFile($sourceFile, "<?php\nline1\nline2\nline3\nline4\nline5\n");
+
+        try {
+            $throwable = new Exception('trace');
+            $this->setPrivateProperty($throwable, 'file', $sourceFile);
+            $this->setPrivateProperty($throwable, 'line', 3);
+            $this->setPrivateProperty($throwable, 'trace', [
+                ['class' => ErrorHandler::class, 'file' => $sourceFile, 'line' => 2],
+                ['class' => 'ExternalClass', 'file' => $sourceFile, 'line' => 4],
+                ['class' => 'NoFileClass'],
+            ]);
+
+            $trace = $this->formatter->compose($throwable);
+
+            $this->assertCount(2, $trace);
+            $this->assertSame($sourceFile, $trace[0]['file']);
+            $this->assertStringContainsString('<ol start="1">', $trace[0]['code']);
+            $this->assertStringContainsString('class="error-line"', $trace[0]['code']);
+            $this->assertSame($sourceFile, $trace[1]['file']);
+            $this->assertStringContainsString('class="switch-line"', $trace[1]['code']);
+        } finally {
+            $this->removeFile($sourceFile);
+        }
+    }
+
+    public function testGetSourceCodeReturnsEmptyStringForNonLocalAdapter(): void
+    {
+        $adapter = Mockery::mock(FilesystemAdapterInterface::class);
+
+        $factory = Di::get(FileSystemFactory::class);
+        $instancesProperty = new ReflectionProperty(FileSystemFactory::class, 'instances');
+        $instancesProperty->setAccessible(true);
+        $originalInstances = $instancesProperty->getValue($factory);
+
+        try {
+            $instancesProperty->setValue($factory, ['local' => new FileSystem($adapter)]);
+
+            $code = $this->formatter->getSourceCode(__FILE__, 10, 'error-line');
+
+            $this->assertSame('', $code);
+        } finally {
+            $instancesProperty->setValue($factory, $originalInstances);
+        }
+    }
+}
diff --git a/tests/Unit/Tracer/WebExceptionRendererTest.php b/tests/Unit/Tracer/WebExceptionRendererTest.php
new file mode 100644
index 000000000..d19f1d4f5
--- /dev/null
+++ b/tests/Unit/Tracer/WebExceptionRendererTest.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Quantum\Tests\Unit\Tracer;
+
+use Quantum\Tracer\WebExceptionRenderer;
+use Quantum\Tests\Unit\AppTestCase;
+use Exception;
+
+class WebExceptionRendererTest extends AppTestCase
+{
+    public function testRenderDebugModeUsesTraceTemplateAndSeverity(): void
+    {
+        config()->set('app.debug', true);
+
+        $renderer = new WebExceptionRenderer();
+        $html = $renderer->render(new Exception('Debug renderer failure'), 'warning');
+
+        $this->assertStringContainsString('TRACE VIEW', $html);
+        $this->assertStringContainsString('Warning :: Debug renderer failure', $html);
+    }
+
+    public function testRenderProductionModeUses500Template(): void
+    {
+        config()->set('app.debug', false);
+
+        $renderer = new WebExceptionRenderer();
+        $html = $renderer->render(new Exception('Prod renderer failure'), 'error');
+
+        $this->assertStringContainsString('ERROR 500 VIEW', $html);
+    }
+}