diff --git a/tests/Handler/TextDocumentSyncHandlerTest.php b/tests/Handler/TextDocumentSyncHandlerTest.php
new file mode 100644
index 00000000..30b4c247
--- /dev/null
+++ b/tests/Handler/TextDocumentSyncHandlerTest.php
@@ -0,0 +1,169 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Firehed\PhpLsp\Tests\Handler;
+
+use Firehed\PhpLsp\Cache\InvalidatableInterface;
+use Firehed\PhpLsp\Document\DocumentManagerInterface;
+use Firehed\PhpLsp\Document\TextDocument;
+use Firehed\PhpLsp\Handler\TextDocumentSyncHandler;
+use Firehed\PhpLsp\Knowledge\SymbolSinkInterface;
+use Firehed\PhpLsp\Protocol\NotificationMessage;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(TextDocumentSyncHandler::class)]
+class TextDocumentSyncHandlerTest extends TestCase
+{
+    private const URI = 'file:///test.php';
+
+    public function testSupports(): void
+    {
+        $handler = new TextDocumentSyncHandler(
+            self::createStub(DocumentManagerInterface::class),
+            self::createStub(SymbolSinkInterface::class),
+            self::createStub(InvalidatableInterface::class),
+        );
+
+        self::assertTrue($handler->supports('textDocument/didOpen'), 'didOpen is handled');
+        self::assertTrue($handler->supports('textDocument/didChange'), 'didChange is handled');
+        self::assertTrue($handler->supports('textDocument/didClose'), 'didClose is handled');
+        self::assertFalse(
+            $handler->supports('textDocument/hover'),
+            'the handler does not claim any other method',
+        );
+    }
+
+    public function testHandleDidOpenRegistersWithTheManagerThenForwardsTheDocumentToTheSink(): void
+    {
+        $document = new TextDocument(self::URI, 'php', 1, '<?php echo "hello";');
+
+        $documents = $this->createMock(DocumentManagerInterface::class);
+        $documents
+            ->expects($this->once())
+            ->method('open')
+            ->with(self::URI, 'php', 1, '<?php echo "hello";');
+        $documents
+            ->expects($this->once())
+            ->method('get')
+            ->with(self::URI)
+            ->willReturn($document);
+        $documents->expects($this->never())->method('update');
+        $documents->expects($this->never())->method('close');
+
+        $symbols = $this->createMock(SymbolSinkInterface::class);
+        $symbols->expects($this->once())->method('openDocument')->with($document);
+        $symbols->expects($this->never())->method('updateDocument');
+        $symbols->expects($this->never())->method('closeDocument');
+
+        $invalidator = $this->createMock(InvalidatableInterface::class);
+        $invalidator->expects($this->never())->method('invalidate');
+
+        $handler = new TextDocumentSyncHandler($documents, $symbols, $invalidator);
+        $handler->handle(NotificationMessage::fromArray([
+            'jsonrpc' => '2.0',
+            'method' => 'textDocument/didOpen',
+            'params' => [
+                'textDocument' => [
+                    'uri' => self::URI,
+                    'languageId' => 'php',
+                    'version' => 1,
+                    'text' => '<?php echo "hello";',
+                ],
+            ],
+        ]));
+    }
+
+    public function testHandleDidChangeAppliesTheLastContentChangeThroughTheManagerAndSink(): void
+    {
+        $document = new TextDocument(self::URI, 'php', 2, '<?php echo "v2";');
+
+        $documents = $this->createMock(DocumentManagerInterface::class);
+        $documents
+            ->expects($this->once())
+            ->method('update')
+            ->with(self::URI, '<?php echo "v2";', 2);
+        $documents
+            ->expects($this->once())
+            ->method('get')
+            ->with(self::URI)
+            ->willReturn($document);
+        $documents->expects($this->never())->method('open');
+        $documents->expects($this->never())->method('close');
+
+        $symbols = $this->createMock(SymbolSinkInterface::class);
+        $symbols->expects($this->once())->method('updateDocument')->with($document);
+        $symbols->expects($this->never())->method('openDocument');
+        $symbols->expects($this->never())->method('closeDocument');
+
+        $invalidator = $this->createMock(InvalidatableInterface::class);
+        $invalidator->expects($this->never())->method('invalidate');
+
+        $handler = new TextDocumentSyncHandler($documents, $symbols, $invalidator);
+        $handler->handle(NotificationMessage::fromArray([
+            'jsonrpc' => '2.0',
+            'method' => 'textDocument/didChange',
+            'params' => [
+                'textDocument' => ['uri' => self::URI, 'version' => 2],
+                // Only the last change's text is applied (full-sync; LSP §Document Synchronization).
+                'contentChanges' => [
+                    ['text' => '<?php echo "v1-skipped";'],
+                    ['text' => '<?php echo "v2";'],
+                ],
+            ],
+        ]));
+    }
+
+    public function testHandleDidChangeIsANoOpWhenContentChangesIsEmpty(): void
+    {
+        $documents = $this->createMock(DocumentManagerInterface::class);
+        $documents->expects($this->never())->method('update');
+        $documents->expects($this->never())->method('get');
+
+        $symbols = $this->createMock(SymbolSinkInterface::class);
+        $symbols->expects($this->never())->method('updateDocument');
+
+        $invalidator = $this->createMock(InvalidatableInterface::class);
+        $invalidator->expects($this->never())->method('invalidate');
+
+        $handler = new TextDocumentSyncHandler($documents, $symbols, $invalidator);
+        $handler->handle(NotificationMessage::fromArray([
+            'jsonrpc' => '2.0',
+            'method' => 'textDocument/didChange',
+            'params' => [
+                'textDocument' => ['uri' => self::URI, 'version' => 2],
+                'contentChanges' => [],
+            ],
+        ]));
+    }
+
+    public function testHandleDidCloseInvalidatesAndClosesAcrossAllThreeCollaborators(): void
+    {
+        $documents = $this->createMock(DocumentManagerInterface::class);
+        $documents->expects($this->once())->method('close')->with(self::URI);
+        $documents->expects($this->never())->method('open');
+        $documents->expects($this->never())->method('update');
+
+        $symbols = $this->createMock(SymbolSinkInterface::class);
+        $symbols->expects($this->once())->method('closeDocument')->with(self::URI);
+        $symbols->expects($this->never())->method('openDocument');
+        $symbols->expects($this->never())->method('updateDocument');
+
+        // The invalidator drop is what makes the next on-disk query re-read disk
+        // rather than the pre-edit cached value (RFC 1 §5.3). Covered here at the
+        // handler boundary; the fan-out through composite invalidators lives in
+        // the integration test.
+        $invalidator = $this->createMock(InvalidatableInterface::class);
+        $invalidator->expects($this->once())->method('invalidate')->with(self::URI);
+
+        $handler = new TextDocumentSyncHandler($documents, $symbols, $invalidator);
+        $handler->handle(NotificationMessage::fromArray([
+            'jsonrpc' => '2.0',
+            'method' => 'textDocument/didClose',
+            'params' => [
+                'textDocument' => ['uri' => self::URI],
+            ],
+        ]));
+    }
+}
diff --git a/tests/Integration/TextDocumentSyncHandlerIntegrationTest.php b/tests/Integration/TextDocumentSyncHandlerIntegrationTest.php
index 82812158..69498457 100644
--- a/tests/Integration/TextDocumentSyncHandlerIntegrationTest.php
+++ b/tests/Integration/TextDocumentSyncHandlerIntegrationTest.php
@@ -4,7 +4,6 @@
 
 namespace Firehed\PhpLsp\Tests\Integration;
 
-use Firehed\PhpLsp\Cache\InvalidatableInterface;
 use Firehed\PhpLsp\Document\DocumentManager;
 use Firehed\PhpLsp\Domain\ClasslikeName;
 use Firehed\PhpLsp\Domain\ComposerAutoloadMap;
@@ -39,14 +38,6 @@ protected function setUp(): void
         $this->handler = new TextDocumentSyncHandler($this->manager, $knowledge->sink, $knowledge->invalidator);
     }
 
-    public function testSupports(): void
-    {
-        self::assertTrue($this->handler->supports('textDocument/didOpen'));
-        self::assertTrue($this->handler->supports('textDocument/didChange'));
-        self::assertTrue($this->handler->supports('textDocument/didClose'));
-        self::assertFalse($this->handler->supports('textDocument/hover'));
-    }
-
     public function testDidOpen(): void
     {
         $notification = NotificationMessage::fromArray([
@@ -209,31 +200,6 @@ public function testDidChangeUpdatesClasses(): void
         self::assertSame('NewClass', $newClass->name->qualifiedName->shortName);
     }
 
-    public function testDidCloseInvalidatesTheOnDiskCacheSoTheNextQueryReReadsDisk(): void
-    {
-        // Closing an edited file must drop the on-disk cache so the next query
-        // reflects disk rather than the pre-edit cached value (RFC 1 §5.3).
-        $uri = 'file:///workspace/src/Widget.php';
-        $this->manager->open($uri, 'php', 1, '<?php');
-
-        $invalidator = $this->createMock(InvalidatableInterface::class);
-        $invalidator->expects($this->once())
-            ->method('invalidate')
-            ->with($uri);
-
-        $production = ProductionSyntaxSource::create();
-        $knowledge = $this->knowledgeStackForMap(new ComposerAutoloadMap(), $production);
-        $handler = new TextDocumentSyncHandler($this->manager, $knowledge->sink, $invalidator);
-
-        $handler->handle(NotificationMessage::fromArray([
-            'jsonrpc' => '2.0',
-            'method' => 'textDocument/didClose',
-            'params' => [
-                'textDocument' => ['uri' => $uri],
-            ],
-        ]));
-    }
-
     public function testDidCloseRemovesClasses(): void
     {
         /** @var class-string $className */