diff --git a/apps/server/src/modules/board/service/media-board/media-board.service.spec.ts b/apps/server/src/modules/board/service/media-board/media-board.service.spec.ts
new file mode 100644
index 00000000000..bb7934c4f0a
--- /dev/null
+++ b/apps/server/src/modules/board/service/media-board/media-board.service.spec.ts
@@ -0,0 +1,163 @@
+import { Test, TestingModule } from '@nestjs/testing';
+import { createMock, DeepMocked } from '@golevelup/ts-jest';
+import { ContextExternalToolService } from '@modules/tool/context-external-tool/service';
+import { schoolExternalToolFactory } from '@modules/tool/school-external-tool/testing';
+import { contextExternalToolFactory } from '@modules/tool/context-external-tool/testing';
+import { mediaBoardFactory, mediaExternalToolElementFactory, mediaLineFactory } from '../../testing';
+import { BoardExternalReference, BoardExternalReferenceType, BoardLayout, MediaBoardColors } from '../../domain';
+import { BoardNodeRepo } from '../../repo';
+import { MediaBoardService } from './media-board.service';
+
+describe('MediaBoardService', () => {
+	let module: TestingModule;
+	let service: MediaBoardService;
+	let boardNodeRepo: DeepMocked<BoardNodeRepo>;
+	let contextExternalToolService: DeepMocked<ContextExternalToolService>;
+
+	beforeAll(async () => {
+		module = await Test.createTestingModule({
+			providers: [
+				MediaBoardService,
+				{
+					provide: BoardNodeRepo,
+					useValue: createMock<BoardNodeRepo>(),
+				},
+				{
+					provide: ContextExternalToolService,
+					useValue: createMock<ContextExternalToolService>(),
+				},
+			],
+		}).compile();
+
+		service = module.get<MediaBoardService>(MediaBoardService);
+		boardNodeRepo = module.get(BoardNodeRepo);
+		contextExternalToolService = module.get(ContextExternalToolService);
+	});
+
+	afterAll(async () => {
+		await module.close();
+	});
+
+	beforeEach(() => {
+		jest.resetAllMocks();
+	});
+
+	describe('findByExternalReference', () => {
+		const setup = () => {
+			const mediaBoard = mediaBoardFactory.build();
+			boardNodeRepo.findByExternalReference.mockResolvedValueOnce([mediaBoard]);
+			return { mediaBoard };
+		};
+		it('should call boardNodeRepo.findByExternalReference', async () => {
+			const reference: BoardExternalReference = { type: BoardExternalReferenceType.User, id: 'id' };
+			await service.findByExternalReference(reference);
+			expect(boardNodeRepo.findByExternalReference).toHaveBeenCalledWith(reference);
+		});
+		it('should return MediaBoard', async () => {
+			const { mediaBoard } = setup();
+			const reference: BoardExternalReference = { type: BoardExternalReferenceType.User, id: 'id' };
+			const result = await service.findByExternalReference(reference);
+			expect(result).toEqual([mediaBoard]);
+		});
+	});
+
+	describe('checkElementExists', () => {
+		describe('when element does not exist', () => {
+			const setup = () => {
+				const schoolExternalTool = schoolExternalToolFactory.build();
+				const contextExternalTool = contextExternalToolFactory.build({ schoolToolRef: schoolExternalTool });
+				const mediaExternalToolElement = mediaExternalToolElementFactory.build({
+					contextExternalToolId: contextExternalTool.id,
+				});
+				const mediaLine = mediaLineFactory.build({ children: [mediaExternalToolElement] });
+				const mediaBoard = mediaBoardFactory.build({ children: [mediaLine] });
+
+				contextExternalToolService.findContextExternalTools.mockResolvedValue([]);
+
+				return { schoolExternalTool, mediaBoard };
+			};
+			it('should call findContextExternalTools', async () => {
+				const schoolExternalTool = schoolExternalToolFactory.build();
+				const mediaBoard = mediaBoardFactory.build();
+				contextExternalToolService.findContextExternalTools.mockResolvedValue([]);
+				await service.checkElementExists(mediaBoard, schoolExternalTool);
+				expect(contextExternalToolService.findContextExternalTools).toHaveBeenCalledWith({
+					schoolToolRef: { schoolToolId: schoolExternalTool.id },
+				});
+			});
+			it('should return false if element does not exist in MediaBoard', async () => {
+				const { schoolExternalTool, mediaBoard } = setup();
+				const exists = await service.checkElementExists(mediaBoard, schoolExternalTool);
+				expect(exists).toBe(false);
+			});
+		});
+
+		describe('when element exists', () => {
+			const setup = () => {
+				const schoolExternalTool = schoolExternalToolFactory.build();
+				const contextExternalTool = contextExternalToolFactory.build({ schoolToolRef: schoolExternalTool });
+				const mediaExternalToolElement = mediaExternalToolElementFactory.build({
+					contextExternalToolId: contextExternalTool.id,
+				});
+				const mediaLine = mediaLineFactory.build({ children: [mediaExternalToolElement] });
+				const mediaBoard = mediaBoardFactory.build({ children: [mediaLine] });
+
+				contextExternalToolService.findContextExternalTools.mockResolvedValue([contextExternalTool]);
+
+				return { schoolExternalTool, mediaBoard };
+			};
+			it('should return true if element exists in MediaBoard', async () => {
+				const { schoolExternalTool, mediaBoard } = setup();
+				const exists = await service.checkElementExists(mediaBoard, schoolExternalTool);
+				expect(exists).toBe(true);
+			});
+		});
+	});
+
+	describe('createContextExternalToolForMediaBoard', () => {
+		const setup = () => {
+			const mediaBoard = mediaBoardFactory.build();
+			const schoolExternalTool = schoolExternalToolFactory.build();
+			const contextExternalTool = contextExternalToolFactory.build();
+			contextExternalToolService.saveContextExternalTool.mockResolvedValue(contextExternalTool);
+			return { mediaBoard, schoolExternalTool, contextExternalTool };
+		};
+		it('should call saveContextExternalTool', async () => {
+			const { mediaBoard, schoolExternalTool } = setup();
+			await service.createContextExternalToolForMediaBoard('1', schoolExternalTool, mediaBoard);
+			expect(contextExternalToolService.saveContextExternalTool).toHaveBeenCalled();
+		});
+		it('should return contextExternalTool', async () => {
+			const { mediaBoard, schoolExternalTool, contextExternalTool } = setup();
+			const result = await service.createContextExternalToolForMediaBoard('1', schoolExternalTool, mediaBoard);
+			expect(result).toBe(contextExternalTool);
+		});
+	});
+
+	describe('update functions', () => {
+		const setup = () => {
+			const mediaBoard = mediaBoardFactory.build();
+			return { mediaBoard };
+		};
+		it('should update MediaBoard backgroundColor', async () => {
+			const { mediaBoard } = setup();
+			await service.updateBackgroundColor(mediaBoard, MediaBoardColors.TRANSPARENT);
+			expect(mediaBoard.backgroundColor).toBe(MediaBoardColors.TRANSPARENT);
+			expect(boardNodeRepo.save).toHaveBeenCalledWith(mediaBoard);
+		});
+
+		it('should update MediaBoard collapsed state', async () => {
+			const { mediaBoard } = setup();
+			await service.updateCollapsed(mediaBoard, true);
+			expect(mediaBoard.collapsed).toBe(true);
+			expect(boardNodeRepo.save).toHaveBeenCalledWith(mediaBoard);
+		});
+
+		it('should update MediaBoard layout', async () => {
+			const { mediaBoard } = setup();
+			await service.updateLayout(mediaBoard, BoardLayout.GRID);
+			expect(mediaBoard.layout).toBe(BoardLayout.GRID);
+			expect(boardNodeRepo.save).toHaveBeenCalledWith(mediaBoard);
+		});
+	});
+});
diff --git a/apps/server/src/modules/board/service/media-board/media-board.service.ts b/apps/server/src/modules/board/service/media-board/media-board.service.ts
index fb58eb459b0..7949aeb2f5f 100644
--- a/apps/server/src/modules/board/service/media-board/media-board.service.ts
+++ b/apps/server/src/modules/board/service/media-board/media-board.service.ts
@@ -30,9 +30,9 @@ export class MediaBoardService {
 	async findByExternalReference(reference: BoardExternalReference): Promise<MediaBoard[]> {
 		const boardNodes = await this.boardNodeRepo.findByExternalReference(reference);
 
-		const boards = boardNodes.filter((bn) => isMediaBoard(bn));
+		const boards = boardNodes.filter((bn): bn is MediaBoard => isMediaBoard(bn));
 
-		return boards as MediaBoard[];
+		return boards;
 	}
 
 	public async createContextExternalToolForMediaBoard(