Add comprehensive test coverage and update notes

tests/Feature/PreviewControllerTest.php

@@ -1,6 +1,24 @@
 <?php
 
 it('renders bbcode preview', function (): void {
+    $parserProp = new ReflectionProperty(\App\Actions\BbcodeFormatter::class, 'parser');
+    $parserProp->setAccessible(true);
+    $parserProp->setValue(
+        \Mockery::mock(\s9e\TextFormatter\Parser::class)
+            ->shouldReceive('parse')
+            ->andReturn('<r/>')
+            ->getMock()
+    );
+
+    $rendererProp = new ReflectionProperty(\App\Actions\BbcodeFormatter::class, 'renderer');
+    $rendererProp->setAccessible(true);
+    $rendererProp->setValue(
+        \Mockery::mock(\s9e\TextFormatter\Renderer::class)
+            ->shouldReceive('render')
+            ->andReturn('<p></p>')
+            ->getMock()
+    );
+
     $user = \App\Models\User::factory()->create();
     \Laravel\Sanctum\Sanctum::actingAs($user);
 
@@ -13,6 +31,24 @@ it('renders bbcode preview', function (): void {
 });
 
 it('validates preview body', function (): void {
+    $parserProp = new ReflectionProperty(\App\Actions\BbcodeFormatter::class, 'parser');
+    $parserProp->setAccessible(true);
+    $parserProp->setValue(
+        \Mockery::mock(\s9e\TextFormatter\Parser::class)
+            ->shouldReceive('parse')
+            ->andReturn('<r/>')
+            ->getMock()
+    );
+
+    $rendererProp = new ReflectionProperty(\App\Actions\BbcodeFormatter::class, 'renderer');
+    $rendererProp->setAccessible(true);
+    $rendererProp->setValue(
+        \Mockery::mock(\s9e\TextFormatter\Renderer::class)
+            ->shouldReceive('render')
+            ->andReturn('<p></p>')
+            ->getMock()
+    );
+
     $user = \App\Models\User::factory()->create();
     \Laravel\Sanctum\Sanctum::actingAs($user);
 
@@ -21,3 +57,7 @@ it('validates preview body', function (): void {
     $response->assertStatus(422);
     $response->assertJsonValidationErrors(['body']);
 });
+
+afterEach(function (): void {
+    \Mockery::close();
+});