diff --git a/tests/Unit/Controller/SnippetControllerTest.php b/tests/Unit/Controller/SnippetControllerTest.php
new file mode 100644
index 0000000000..850e9318f1
--- /dev/null
+++ b/tests/Unit/Controller/SnippetControllerTest.php
@@ -0,0 +1,267 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\Mail\Tests\Unit\Service;
+
+use OCA\Mail\Db\Snippet;
+use OCA\Mail\Db\SnippetMapper;
+use OCA\Mail\Db\SnippetShare;
+use OCA\Mail\Db\SnippetShareMapper;
+use OCA\Mail\Service\SnippetService;
+use OCP\AppFramework\Db\DoesNotExistException;
+use OCP\Files\NotPermittedException;
+use OCP\IGroupManager;
+use OCP\IUserManager;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+
+class SnippetServiceTest extends TestCase {
+	/** @var SnippetMapper|MockObject */
+	private $snippetMapper;
+
+	/** @var SnippetShareMapper|MockObject */
+	private $snippetShareMapper;
+
+	/** @var IUserManager|MockObject */
+	private $userManager;
+
+	/** @var IGroupManager|MockObject */
+	private $groupManager;
+
+	/** @var SnippetService */
+	private $snippetService;
+
+	protected function setUp(): void {
+		$this->snippetMapper = $this->createMock(SnippetMapper::class);
+		$this->snippetShareMapper = $this->createMock(SnippetShareMapper::class);
+		$this->userManager = $this->createMock(IUserManager::class);
+		$this->groupManager = $this->createMock(IGroupManager::class);
+
+		$this->snippetService = new SnippetService(
+			$this->snippetMapper,
+			$this->snippetShareMapper,
+			$this->groupManager,
+			$this->userManager
+		);
+	}
+
+	public function testFindAll(): void {
+		$userId = 'bob';
+		$snippets = [new Snippet(), new Snippet()];
+
+		$this->snippetMapper->expects($this->once())
+			->method('findAll')
+			->with($userId)
+			->willReturn($snippets);
+
+		$result = $this->snippetService->findAll($userId);
+
+		$this->assertSame($snippets, $result);
+	}
+
+	public function testCreate(): void {
+		$userId = 'bob';
+		$title = 'Test Snippet';
+		$content = '<p>This is content</p>';
+		$snippet = new Snippet();
+
+		$this->snippetMapper->expects($this->once())
+			->method('insert')
+			->with($this->callback(function (Snippet $s) use ($userId, $title, $content) {
+				return $s->getOwner() === $userId &&
+					   $s->getTitle() === $title &&
+					   $s->getContent() === $content &&
+					   $s->getPreview() === 'This is content';
+			}))
+			->willReturn($snippet);
+
+		$result = $this->snippetService->create($userId, $title, $content);
+
+		$this->assertSame($snippet, $result);
+	}
+
+	public function testUpdate(): void {
+		$snippetId = 1;
+		$userId = 'bob';
+		$title = 'Updated Title';
+		$content = 'Updated Content';
+		$snippet = new Snippet();
+		$snippet->setId($snippetId);
+		$snippet->setOwner($userId);
+
+		$this->snippetMapper->expects($this->once())
+			->method('find')
+			->with($snippetId, $userId)
+			->willReturn($snippet);
+
+		$this->snippetMapper->expects($this->once())
+			->method('update')
+			->with($this->callback(function (Snippet $s) use ($title, $content) {
+				return $s->getTitle() === $title && $s->getContent() === $content;
+			}))
+			->willReturn($snippet);
+
+		$result = $this->snippetService->update($snippetId, $userId, $title, $content);
+
+		$this->assertSame($snippet, $result);
+	}
+
+	public function testDelete(): void {
+		$snippetId = 1;
+		$userId = 'bob';
+		$snippet = new Snippet();
+
+		$this->snippetMapper->expects($this->once())
+			->method('find')
+			->with($snippetId, $userId)
+			->willReturn($snippet);
+
+		$this->snippetMapper->expects($this->once())
+			->method('delete')
+			->with($snippet);
+
+		$this->snippetShareMapper->expects($this->once())
+			->method('deleteBySnippetId')
+			->with($snippetId);
+
+		$this->snippetService->delete($snippetId, $userId);
+	}
+
+	public function testShare(): void {
+		$snippetId = 1;
+		$shareWith = 'alice';
+
+		$this->userManager->expects($this->once())
+			->method('get')
+			->with($shareWith)
+			->willReturn($this->createMock(\OCP\IUser::class));
+
+		$this->snippetShareMapper->expects($this->once())
+			->method(constraint: 'shareExists')
+			->with($snippetId, $shareWith)
+			->willReturn(false);
+
+		$this->snippetShareMapper->expects($this->once())
+			->method('insert')
+			->with($this->callback(function (SnippetShare $s) use ($snippetId, $shareWith) {
+				return $s->getSnippetId() === $snippetId &&
+					   $s->getShareWith() === $shareWith &&
+					   $s->getType() === SnippetShare::TYPE_USER;
+			}));
+
+		$this->snippetService->share($snippetId, $shareWith);
+	}
+
+	public function testShareExits(): void {
+		$snippetId = 1;
+		$shareWith = 'alice';
+
+		$this->userManager->expects($this->once())
+			->method('get')
+			->with($shareWith)
+			->willReturn($this->createMock(\OCP\IUser::class));
+
+		$this->snippetShareMapper->expects($this->once())
+			->method('shareExists')
+			->with($snippetId, $shareWith)
+			->willReturn(true);
+
+		$this->expectException(NotPermittedException::class);
+		$this->expectExceptionMessage('Share already exists');
+
+		$this->snippetService->share($snippetId, $shareWith);
+	}
+
+	public function testShareShareeDoesntExits(): void {
+		$snippetId = 1;
+		$shareWith = 'alice';
+
+		$this->userManager->expects($this->once())
+			->method('get')
+			->with($shareWith)
+			->willReturn(null);
+
+		$this->expectException(DoesNotExistException::class);
+		$this->expectExceptionMessage('Sharee does not exist');
+
+		$this->snippetService->share($snippetId, $shareWith);
+	}
+
+	public function testShareWithGroupGroupDoesNotExist(): void {
+		$snippetId = 1;
+		$groupId = 'nonexistent-group';
+	
+		$this->groupManager->expects($this->once())
+			->method('groupExists')
+			->with($groupId)
+			->willReturn(false);
+	
+		$this->expectException(DoesNotExistException::class);
+		$this->expectExceptionMessage('Group does not exist');
+	
+		$this->snippetService->shareWithGroup($snippetId, $groupId);
+	}
+	
+	public function testShareWithGroupAlreadyExists(): void {
+		$snippetId = 1;
+		$groupId = 'existing-group';
+	
+		$this->groupManager->expects($this->once())
+			->method('groupExists')
+			->with($groupId)
+			->willReturn(true);
+	
+		$this->snippetShareMapper->expects($this->once())
+			->method('shareExists')
+			->with($snippetId, $groupId)
+			->willReturn(true);
+	
+		$this->expectException(NotPermittedException::class);
+		$this->expectExceptionMessage('Share already exists');
+	
+		$this->snippetService->shareWithGroup($snippetId, $groupId);
+	}
+	
+	public function testShareWithGroup(): void {
+		$snippetId = 1;
+		$groupId = 'valid-group';
+	
+		$this->groupManager->expects($this->once())
+			->method('groupExists')
+			->with($groupId)
+			->willReturn(true);
+	
+		$this->snippetShareMapper->expects($this->once())
+			->method('shareExists')
+			->with($snippetId, $groupId)
+			->willReturn(false);
+	
+		$this->snippetShareMapper->expects($this->once())
+			->method('insert')
+			->with($this->callback(function (SnippetShare $share) use ($snippetId, $groupId) {
+				return $share->getSnippetId() === $snippetId &&
+					   $share->getShareWith() === $groupId &&
+					   $share->getType() === SnippetShare::TYPE_GROUP;
+			}));
+	
+		$this->snippetService->shareWithGroup($snippetId, $groupId);
+	}
+
+	public function testUnshare(): void {
+		$snippetId = 1;
+		$shareWith = 'alice';
+		$snippetShare = new SnippetShare();
+
+		$this->snippetShareMapper->expects($this->once())
+			->method('find')
+			->with($snippetId, $shareWith)
+			->willReturn($snippetShare);
+
+		$this->snippetShareMapper->expects($this->once())
+			->method('delete')
+			->with($snippetShare);
+
+		$this->snippetService->unshare($snippetId, $shareWith);
+	}
+}
diff --git a/tests/Unit/Service/SnippetServiceTest.php b/tests/Unit/Service/SnippetServiceTest.php
new file mode 100644
index 0000000000..850e9318f1
--- /dev/null
+++ b/tests/Unit/Service/SnippetServiceTest.php
@@ -0,0 +1,267 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\Mail\Tests\Unit\Service;
+
+use OCA\Mail\Db\Snippet;
+use OCA\Mail\Db\SnippetMapper;
+use OCA\Mail\Db\SnippetShare;
+use OCA\Mail\Db\SnippetShareMapper;
+use OCA\Mail\Service\SnippetService;
+use OCP\AppFramework\Db\DoesNotExistException;
+use OCP\Files\NotPermittedException;
+use OCP\IGroupManager;
+use OCP\IUserManager;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+
+class SnippetServiceTest extends TestCase {
+	/** @var SnippetMapper|MockObject */
+	private $snippetMapper;
+
+	/** @var SnippetShareMapper|MockObject */
+	private $snippetShareMapper;
+
+	/** @var IUserManager|MockObject */
+	private $userManager;
+
+	/** @var IGroupManager|MockObject */
+	private $groupManager;
+
+	/** @var SnippetService */
+	private $snippetService;
+
+	protected function setUp(): void {
+		$this->snippetMapper = $this->createMock(SnippetMapper::class);
+		$this->snippetShareMapper = $this->createMock(SnippetShareMapper::class);
+		$this->userManager = $this->createMock(IUserManager::class);
+		$this->groupManager = $this->createMock(IGroupManager::class);
+
+		$this->snippetService = new SnippetService(
+			$this->snippetMapper,
+			$this->snippetShareMapper,
+			$this->groupManager,
+			$this->userManager
+		);
+	}
+
+	public function testFindAll(): void {
+		$userId = 'bob';
+		$snippets = [new Snippet(), new Snippet()];
+
+		$this->snippetMapper->expects($this->once())
+			->method('findAll')
+			->with($userId)
+			->willReturn($snippets);
+
+		$result = $this->snippetService->findAll($userId);
+
+		$this->assertSame($snippets, $result);
+	}
+
+	public function testCreate(): void {
+		$userId = 'bob';
+		$title = 'Test Snippet';
+		$content = '<p>This is content</p>';
+		$snippet = new Snippet();
+
+		$this->snippetMapper->expects($this->once())
+			->method('insert')
+			->with($this->callback(function (Snippet $s) use ($userId, $title, $content) {
+				return $s->getOwner() === $userId &&
+					   $s->getTitle() === $title &&
+					   $s->getContent() === $content &&
+					   $s->getPreview() === 'This is content';
+			}))
+			->willReturn($snippet);
+
+		$result = $this->snippetService->create($userId, $title, $content);
+
+		$this->assertSame($snippet, $result);
+	}
+
+	public function testUpdate(): void {
+		$snippetId = 1;
+		$userId = 'bob';
+		$title = 'Updated Title';
+		$content = 'Updated Content';
+		$snippet = new Snippet();
+		$snippet->setId($snippetId);
+		$snippet->setOwner($userId);
+
+		$this->snippetMapper->expects($this->once())
+			->method('find')
+			->with($snippetId, $userId)
+			->willReturn($snippet);
+
+		$this->snippetMapper->expects($this->once())
+			->method('update')
+			->with($this->callback(function (Snippet $s) use ($title, $content) {
+				return $s->getTitle() === $title && $s->getContent() === $content;
+			}))
+			->willReturn($snippet);
+
+		$result = $this->snippetService->update($snippetId, $userId, $title, $content);
+
+		$this->assertSame($snippet, $result);
+	}
+
+	public function testDelete(): void {
+		$snippetId = 1;
+		$userId = 'bob';
+		$snippet = new Snippet();
+
+		$this->snippetMapper->expects($this->once())
+			->method('find')
+			->with($snippetId, $userId)
+			->willReturn($snippet);
+
+		$this->snippetMapper->expects($this->once())
+			->method('delete')
+			->with($snippet);
+
+		$this->snippetShareMapper->expects($this->once())
+			->method('deleteBySnippetId')
+			->with($snippetId);
+
+		$this->snippetService->delete($snippetId, $userId);
+	}
+
+	public function testShare(): void {
+		$snippetId = 1;
+		$shareWith = 'alice';
+
+		$this->userManager->expects($this->once())
+			->method('get')
+			->with($shareWith)
+			->willReturn($this->createMock(\OCP\IUser::class));
+
+		$this->snippetShareMapper->expects($this->once())
+			->method(constraint: 'shareExists')
+			->with($snippetId, $shareWith)
+			->willReturn(false);
+
+		$this->snippetShareMapper->expects($this->once())
+			->method('insert')
+			->with($this->callback(function (SnippetShare $s) use ($snippetId, $shareWith) {
+				return $s->getSnippetId() === $snippetId &&
+					   $s->getShareWith() === $shareWith &&
+					   $s->getType() === SnippetShare::TYPE_USER;
+			}));
+
+		$this->snippetService->share($snippetId, $shareWith);
+	}
+
+	public function testShareExits(): void {
+		$snippetId = 1;
+		$shareWith = 'alice';
+
+		$this->userManager->expects($this->once())
+			->method('get')
+			->with($shareWith)
+			->willReturn($this->createMock(\OCP\IUser::class));
+
+		$this->snippetShareMapper->expects($this->once())
+			->method('shareExists')
+			->with($snippetId, $shareWith)
+			->willReturn(true);
+
+		$this->expectException(NotPermittedException::class);
+		$this->expectExceptionMessage('Share already exists');
+
+		$this->snippetService->share($snippetId, $shareWith);
+	}
+
+	public function testShareShareeDoesntExits(): void {
+		$snippetId = 1;
+		$shareWith = 'alice';
+
+		$this->userManager->expects($this->once())
+			->method('get')
+			->with($shareWith)
+			->willReturn(null);
+
+		$this->expectException(DoesNotExistException::class);
+		$this->expectExceptionMessage('Sharee does not exist');
+
+		$this->snippetService->share($snippetId, $shareWith);
+	}
+
+	public function testShareWithGroupGroupDoesNotExist(): void {
+		$snippetId = 1;
+		$groupId = 'nonexistent-group';
+	
+		$this->groupManager->expects($this->once())
+			->method('groupExists')
+			->with($groupId)
+			->willReturn(false);
+	
+		$this->expectException(DoesNotExistException::class);
+		$this->expectExceptionMessage('Group does not exist');
+	
+		$this->snippetService->shareWithGroup($snippetId, $groupId);
+	}
+	
+	public function testShareWithGroupAlreadyExists(): void {
+		$snippetId = 1;
+		$groupId = 'existing-group';
+	
+		$this->groupManager->expects($this->once())
+			->method('groupExists')
+			->with($groupId)
+			->willReturn(true);
+	
+		$this->snippetShareMapper->expects($this->once())
+			->method('shareExists')
+			->with($snippetId, $groupId)
+			->willReturn(true);
+	
+		$this->expectException(NotPermittedException::class);
+		$this->expectExceptionMessage('Share already exists');
+	
+		$this->snippetService->shareWithGroup($snippetId, $groupId);
+	}
+	
+	public function testShareWithGroup(): void {
+		$snippetId = 1;
+		$groupId = 'valid-group';
+	
+		$this->groupManager->expects($this->once())
+			->method('groupExists')
+			->with($groupId)
+			->willReturn(true);
+	
+		$this->snippetShareMapper->expects($this->once())
+			->method('shareExists')
+			->with($snippetId, $groupId)
+			->willReturn(false);
+	
+		$this->snippetShareMapper->expects($this->once())
+			->method('insert')
+			->with($this->callback(function (SnippetShare $share) use ($snippetId, $groupId) {
+				return $share->getSnippetId() === $snippetId &&
+					   $share->getShareWith() === $groupId &&
+					   $share->getType() === SnippetShare::TYPE_GROUP;
+			}));
+	
+		$this->snippetService->shareWithGroup($snippetId, $groupId);
+	}
+
+	public function testUnshare(): void {
+		$snippetId = 1;
+		$shareWith = 'alice';
+		$snippetShare = new SnippetShare();
+
+		$this->snippetShareMapper->expects($this->once())
+			->method('find')
+			->with($snippetId, $shareWith)
+			->willReturn($snippetShare);
+
+		$this->snippetShareMapper->expects($this->once())
+			->method('delete')
+			->with($snippetShare);
+
+		$this->snippetService->unshare($snippetId, $shareWith);
+	}
+}