fix: don't allow invalid class names

src/Exceptions/InvalidTestClassName.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Exceptions;
+
+use InvalidArgumentException;
+use NunoMaduro\Collision\Contracts\RenderlessEditor;
+use NunoMaduro\Collision\Contracts\RenderlessTrace;
+use Symfony\Component\Console\Exception\ExceptionInterface;
+
+/**
+ * @internal
+ */
+final class InvalidTestClassName extends InvalidArgumentException implements ExceptionInterface, RenderlessEditor, RenderlessTrace
+{
+    /**
+     * Creates a new Exception instance for the given class name.
+     */
+    public static function fromClassName(string $filename, string $className): self
+    {
+        return new self(sprintf(
+            'The test file [%s] would create the class [%s], which is not a valid PHP class name. Please rename the test file.',
+            $filename,
+            $className,
+        ));
+    }
+
+    /**
+     * Creates a new Exception instance for the given namespace.
+     */
+    public static function fromNamespace(string $filename, string $namespace, string $part): self
+    {
+        return new self(sprintf(
+            'The test file [%s] would create the namespace [%s], which is not a valid PHP namespace, as [%s] may not be used as a namespace name. Please rename the folder in question.',
+            $filename,
+            $namespace,
+            $part,
+        ));
+    }
+}