minor #487 [Store] Add withContent validation test case (OskarStark)

This PR was merged into the main branch.

Discussion
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[Store] Add `withContent` validation test case

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

Add test case to verify that `TextDocument::withContent()` properly validates the new content parameter and throws InvalidArgumentException when given empty or whitespace-only content.

Commits
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13352b3 [Store] Add withContent validation test case

Author: OskarStark

src/store/tests/Document/TextDocumentTest.php

@@ -265,4 +265,15 @@ public function testWithContent()
         $this->assertSame($metadata, $updatedDocument->metadata);
         $this->assertSame($originalContent, $originalDocument->content);
     }
+
+    #[TestDox('withContent validates new content')]
+    public function testWithContentValidatesContent()
+    {
+        $document = new TextDocument(Uuid::v4(), 'Valid content');
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('The content shall not be an empty string.');
+
+        $document->withContent('   ');
+    }
 }