minor #1672 [Platform][Anthropic] Add test for AssistantMessageNormalizer null content fix (OskarStark)

This PR was merged into the main branch.

Discussion
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[Platform][Anthropic] Add test for `AssistantMessageNormalizer` null content fix

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| Docs?         | no
| Issues        | Follows #1670
| License       | MIT

Commits
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9ee9afe [Platform][Anthropic] Add test for AssistantMessageNormalizer null content fix

Author: chr-hertel

src/platform/tests/Bridge/Anthropic/Contract/AssistantMessageNormalizerTest.php

@@ -0,0 +1,137 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\AI\Platform\Tests\Bridge\Anthropic\Contract;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\AI\Platform\Bridge\Anthropic\Claude;
+use Symfony\AI\Platform\Bridge\Anthropic\Contract\AssistantMessageNormalizer;
+use Symfony\AI\Platform\Contract;
+use Symfony\AI\Platform\Message\AssistantMessage;
+use Symfony\AI\Platform\Result\ToolCall;
+
+/**
+ * @author Oskar Stark <oskarstark@googlemail.com>
+ */
+final class AssistantMessageNormalizerTest extends TestCase
+{
+    private AssistantMessageNormalizer $normalizer;
+
+    protected function setUp(): void
+    {
+        $this->normalizer = new AssistantMessageNormalizer();
+    }
+
+    public function testSupportsNormalization()
+    {
+        $model = new Claude(Claude::HAIKU_35);
+        $context = [Contract::CONTEXT_MODEL => $model];
+
+        $this->assertTrue($this->normalizer->supportsNormalization(new AssistantMessage('content'), null, $context));
+        $this->assertFalse($this->normalizer->supportsNormalization(new AssistantMessage('content'), null, []));
+        $this->assertFalse($this->normalizer->supportsNormalization(new \stdClass(), null, $context));
+    }
+
+    public function testGetSupportedTypes()
+    {
+        $this->assertSame([AssistantMessage::class => true], $this->normalizer->getSupportedTypes(null));
+    }
+
+    public function testNormalizeWithContent()
+    {
+        $message = new AssistantMessage('Hello, I am an assistant.');
+
+        $this->assertSame([
+            'role' => 'assistant',
+            'content' => 'Hello, I am an assistant.',
+        ], $this->normalizer->normalize($message));
+    }
+
+    public function testNormalizeWithNullContentProducesEmptyString()
+    {
+        $message = new AssistantMessage(null);
+
+        $this->assertSame([
+            'role' => 'assistant',
+            'content' => '',
+        ], $this->normalizer->normalize($message));
+    }
+
+    public function testNormalizeWithToolCalls()
+    {
+        $toolCall = new ToolCall('tool-id', 'some_tool', ['param' => 'value']);
+        $message = new AssistantMessage(null, [$toolCall]);
+
+        $this->assertSame([
+            'role' => 'assistant',
+            'content' => [
+                [
+                    'type' => 'tool_use',
+                    'id' => 'tool-id',
+                    'name' => 'some_tool',
+                    'input' => ['param' => 'value'],
+                ],
+            ],
+        ], $this->normalizer->normalize($message));
+    }
+
+    public function testNormalizeWithToolCallsAndContent()
+    {
+        $toolCall = new ToolCall('tool-id', 'some_tool', ['param' => 'value']);
+        $message = new AssistantMessage('Some text before tool use.', [$toolCall]);
+
+        $this->assertSame([
+            'role' => 'assistant',
+            'content' => [
+                ['type' => 'text', 'text' => 'Some text before tool use.'],
+                [
+                    'type' => 'tool_use',
+                    'id' => 'tool-id',
+                    'name' => 'some_tool',
+                    'input' => ['param' => 'value'],
+                ],
+            ],
+        ], $this->normalizer->normalize($message));
+    }
+
+    public function testNormalizeWithThinkingContent()
+    {
+        $message = new AssistantMessage(null, null, 'Let me think about this...', 'sig-abc');
+
+        $this->assertSame([
+            'role' => 'assistant',
+            'content' => [
+                [
+                    'type' => 'thinking',
+                    'thinking' => 'Let me think about this...',
+                    'signature' => 'sig-abc',
+                ],
+            ],
+        ], $this->normalizer->normalize($message));
+    }
+
+    public function testNormalizeWithThinkingContentAndText()
+    {
+        $message = new AssistantMessage('The answer is 42.', null, 'Let me think about this...', 'sig-abc');
+
+        $this->assertSame([
+            'role' => 'assistant',
+            'content' => [
+                [
+                    'type' => 'thinking',
+                    'thinking' => 'Let me think about this...',
+                    'signature' => 'sig-abc',
+                ],
+                ['type' => 'text', 'text' => 'The answer is 42.'],
+            ],
+        ], $this->normalizer->normalize($message));
+    }
+}