diff --git a/server/package.json b/server/package.json
index c4de0e1d4..d24e21864 100755
--- a/server/package.json
+++ b/server/package.json
@@ -6,7 +6,9 @@
 	"type": "module",
 	"scripts": {
 		"test": "NODE_OPTIONS=--experimental-vm-modules jest --coverage",
-		"test:services": "NODE_OPTIONS=--experimental-vm-modules jest --coverage --collectCoverageFrom='src/service/**/*.ts' test/unit/services test/unit/providers/network test/unit/providers/notifications",
+		"test:unit": "NODE_OPTIONS=--experimental-vm-modules jest --coverage --collectCoverageFrom='src/**/*.ts' test/unit",
+		"test:unit:services": "NODE_OPTIONS=--experimental-vm-modules jest --coverage --collectCoverageFrom='src/service/**/*.ts' test/unit/services test/unit/providers/network test/unit/providers/notifications",
+		"test:integration": "NODE_OPTIONS=--experimental-vm-modules jest --no-coverage test/integration",
 		"dev": "nodemon --exec tsx src/index.js",
 		"start": "node --watch ./dist/index.js",
 		"build": "tsc && tsc-alias && cp -r src/templates dist/templates",
diff --git a/server/test/helpers/InMemoryIncidentsRepository.ts b/server/test/helpers/InMemoryIncidentsRepository.ts
new file mode 100644
index 000000000..f76236f89
--- /dev/null
+++ b/server/test/helpers/InMemoryIncidentsRepository.ts
@@ -0,0 +1,138 @@
+import type { IIncidentsRepository } from "../../src/repositories/incidents/IIncidentsRepository.ts";
+import type { Incident, IncidentSummary } from "../../src/types/index.ts";
+import { randomUUID } from "crypto";
+
+export class InMemoryIncidentsRepository implements IIncidentsRepository {
+	private incidents: Incident[] = [];
+
+	async create(incident: Partial<Incident>): Promise<Incident> {
+		const now = new Date().toISOString();
+		const full: Incident = {
+			id: randomUUID(),
+			monitorId: incident.monitorId ?? "",
+			teamId: incident.teamId ?? "",
+			startTime: incident.startTime ?? now,
+			endTime: incident.endTime ?? null,
+			status: incident.status ?? true,
+			message: incident.message ?? null,
+			statusCode: incident.statusCode ?? null,
+			resolutionType: incident.resolutionType ?? null,
+			resolvedBy: incident.resolvedBy ?? null,
+			resolvedByEmail: incident.resolvedByEmail ?? null,
+			comment: incident.comment ?? null,
+			createdAt: now,
+			updatedAt: now,
+		};
+		this.incidents.push(full);
+		return { ...full };
+	}
+
+	async findById(incidentId: string, teamId: string): Promise<Incident> {
+		const incident = this.incidents.find((i) => i.id === incidentId && i.teamId === teamId);
+		if (!incident) {
+			throw new Error(`Incident ${incidentId} not found`);
+		}
+		return { ...incident };
+	}
+
+	async findActiveByIncidentId(incidentId: string, teamId: string): Promise<Incident | null> {
+		const incident = this.incidents.find((i) => i.id === incidentId && i.teamId === teamId && i.status === true);
+		return incident ? { ...incident } : null;
+	}
+
+	async findActiveByMonitorId(monitorId: string, teamId: string): Promise<Incident | null> {
+		const incident = this.incidents.find((i) => i.monitorId === monitorId && i.teamId === teamId && i.status === true);
+		return incident ? { ...incident } : null;
+	}
+
+	async findByTeamId(
+		teamId: string,
+		startDate: Date | undefined,
+		page: number,
+		rowsPerPage: number,
+		sortOrder?: string,
+		status?: boolean,
+		monitorId?: string,
+		resolutionType?: string
+	): Promise<Incident[]> {
+		let results = this.incidents.filter((i) => i.teamId === teamId);
+		if (startDate) {
+			results = results.filter((i) => new Date(i.startTime) >= startDate);
+		}
+		if (status !== undefined) {
+			results = results.filter((i) => i.status === status);
+		}
+		if (monitorId) {
+			results = results.filter((i) => i.monitorId === monitorId);
+		}
+		if (resolutionType) {
+			results = results.filter((i) => i.resolutionType === resolutionType);
+		}
+		results.sort((a, b) => {
+			const cmp = new Date(a.startTime).getTime() - new Date(b.startTime).getTime();
+			return sortOrder === "desc" ? -cmp : cmp;
+		});
+		return results.slice(page * rowsPerPage, (page + 1) * rowsPerPage).map((i) => ({ ...i }));
+	}
+
+	async findSummaryByTeamId(_teamId: string, _limit?: number): Promise<IncidentSummary> {
+		throw new Error("Not implemented");
+	}
+
+	async countByTeamId(teamId: string, startDate: Date | undefined, status?: boolean, monitorId?: string, resolutionType?: string): Promise<number> {
+		let results = this.incidents.filter((i) => i.teamId === teamId);
+		if (startDate) {
+			results = results.filter((i) => new Date(i.startTime) >= startDate);
+		}
+		if (status !== undefined) {
+			results = results.filter((i) => i.status === status);
+		}
+		if (monitorId) {
+			results = results.filter((i) => i.monitorId === monitorId);
+		}
+		if (resolutionType) {
+			results = results.filter((i) => i.resolutionType === resolutionType);
+		}
+		return results.length;
+	}
+
+	async updateById(incidentId: string, teamId: string, updateData: Partial<Incident>): Promise<Incident> {
+		const index = this.incidents.findIndex((i) => i.id === incidentId && i.teamId === teamId);
+		if (index === -1) {
+			throw new Error(`Incident ${incidentId} not found`);
+		}
+		const updated: Incident = {
+			...this.incidents[index],
+			...updateData,
+			id: this.incidents[index].id,
+			monitorId: this.incidents[index].monitorId,
+			teamId: this.incidents[index].teamId,
+			createdAt: this.incidents[index].createdAt,
+			updatedAt: new Date().toISOString(),
+		};
+		this.incidents[index] = updated;
+		return { ...updated };
+	}
+
+	async deleteByMonitorId(monitorId: string, teamId: string): Promise<number> {
+		const before = this.incidents.length;
+		this.incidents = this.incidents.filter((i) => !(i.monitorId === monitorId && i.teamId === teamId));
+		return before - this.incidents.length;
+	}
+
+	async deleteByMonitorIdsNotIn(monitorIds: string[]): Promise<number> {
+		const before = this.incidents.length;
+		this.incidents = this.incidents.filter((i) => monitorIds.includes(i.monitorId));
+		return before - this.incidents.length;
+	}
+
+	// Test helpers — not part of the interface
+
+	getAll(): Incident[] {
+		return this.incidents.map((i) => ({ ...i }));
+	}
+
+	clear(): void {
+		this.incidents = [];
+	}
+}
diff --git a/server/test/helpers/InMemoryMonitorsRepository.ts b/server/test/helpers/InMemoryMonitorsRepository.ts
new file mode 100644
index 000000000..88b146914
--- /dev/null
+++ b/server/test/helpers/InMemoryMonitorsRepository.ts
@@ -0,0 +1,116 @@
+import type { IMonitorsRepository, TeamQueryConfig, SummaryConfig } from "../../src/repositories/monitors/IMonitorsRepository.ts";
+import type { Monitor, MonitorsSummary } from "../../src/types/index.ts";
+
+export class InMemoryMonitorsRepository implements IMonitorsRepository {
+	private monitors: Monitor[] = [];
+
+	async create(monitor: Monitor, _teamId: string, _userId: string): Promise<Monitor> {
+		this.monitors.push({ ...monitor });
+		return { ...monitor };
+	}
+
+	async createMonitors(monitors: Monitor[]): Promise<Monitor[]> {
+		const created = monitors.map((m) => ({ ...m }));
+		this.monitors.push(...created);
+		return created;
+	}
+
+	async findById(monitorId: string, teamId: string): Promise<Monitor> {
+		const monitor = this.monitors.find((m) => m.id === monitorId && m.teamId === teamId);
+		if (!monitor) {
+			throw new Error(`Monitor ${monitorId} not found`);
+		}
+		return { ...monitor };
+	}
+
+	async findAll(): Promise<Monitor[]> {
+		return this.monitors.map((m) => ({ ...m }));
+	}
+
+	async findByTeamId(_teamId: string, _config: TeamQueryConfig): Promise<Monitor[]> {
+		return this.monitors.filter((m) => m.teamId === _teamId).map((m) => ({ ...m }));
+	}
+
+	async findByIds(monitorIds: string[]): Promise<Monitor[]> {
+		return this.monitors.filter((m) => monitorIds.includes(m.id)).map((m) => ({ ...m }));
+	}
+
+	async findByIdsWithChecks(monitorIds: string[], _checksCount?: number): Promise<Monitor[]> {
+		return this.findByIds(monitorIds);
+	}
+
+	async updateById(monitorId: string, teamId: string, updates: Partial<Monitor>): Promise<Monitor> {
+		const index = this.monitors.findIndex((m) => m.id === monitorId && m.teamId === teamId);
+		if (index === -1) {
+			throw new Error(`Monitor ${monitorId} not found`);
+		}
+		const updated = { ...this.monitors[index], ...updates, id: this.monitors[index].id, teamId: this.monitors[index].teamId };
+		this.monitors[index] = updated;
+		return { ...updated };
+	}
+
+	async togglePauseById(monitorId: string, teamId: string): Promise<Monitor> {
+		const monitor = await this.findById(monitorId, teamId);
+		const newStatus = monitor.status === "paused" ? "up" : "paused";
+		return this.updateById(monitorId, teamId, { status: newStatus });
+	}
+
+	async deleteById(monitorId: string, teamId: string): Promise<Monitor> {
+		const index = this.monitors.findIndex((m) => m.id === monitorId && m.teamId === teamId);
+		if (index === -1) {
+			throw new Error(`Monitor ${monitorId} not found`);
+		}
+		const [deleted] = this.monitors.splice(index, 1);
+		return { ...deleted };
+	}
+
+	async deleteByTeamId(teamId: string): Promise<{ monitors: Monitor[]; deletedCount: number }> {
+		const toDelete = this.monitors.filter((m) => m.teamId === teamId);
+		this.monitors = this.monitors.filter((m) => m.teamId !== teamId);
+		return { monitors: toDelete, deletedCount: toDelete.length };
+	}
+
+	async findMonitorCountByTeamIdAndType(teamId: string, _config: TeamQueryConfig): Promise<number> {
+		return this.monitors.filter((m) => m.teamId === teamId).length;
+	}
+
+	async findMonitorsSummaryByTeamId(_teamId: string, _config?: SummaryConfig): Promise<MonitorsSummary> {
+		throw new Error("Not implemented");
+	}
+
+	async findGroupsByTeamId(_teamId: string): Promise<string[]> {
+		throw new Error("Not implemented");
+	}
+
+	async removeNotificationFromMonitors(_notificationId: string): Promise<void> {
+		throw new Error("Not implemented");
+	}
+
+	async updateNotifications(_teamId: string, _monitorIds: string[], _notificationIds: string[], _action: "add" | "remove" | "set"): Promise<number> {
+		throw new Error("Not implemented");
+	}
+
+	async deleteByTeamIdsNotIn(teamIds: string[]): Promise<number> {
+		const before = this.monitors.length;
+		this.monitors = this.monitors.filter((m) => teamIds.includes(m.teamId));
+		return before - this.monitors.length;
+	}
+
+	async findAllMonitorIds(): Promise<string[]> {
+		return this.monitors.map((m) => m.id);
+	}
+
+	// Test helpers
+
+	seed(monitor: Monitor): void {
+		this.monitors.push({ ...monitor });
+	}
+
+	getAll(): Monitor[] {
+		return this.monitors.map((m) => ({ ...m }));
+	}
+
+	clear(): void {
+		this.monitors = [];
+	}
+}
diff --git a/server/test/helpers/heartbeatTestHarness.ts b/server/test/helpers/heartbeatTestHarness.ts
new file mode 100644
index 000000000..ec0c3714e
--- /dev/null
+++ b/server/test/helpers/heartbeatTestHarness.ts
@@ -0,0 +1,179 @@
+import { jest } from "@jest/globals";
+import { SuperSimpleQueueHelper } from "../../src/service/infrastructure/SuperSimpleQueue/SuperSimpleQueueHelper.ts";
+import { StatusService } from "../../src/service/infrastructure/statusService.ts";
+import { IncidentService } from "../../src/service/business/incidentService.ts";
+import { InMemoryMonitorsRepository } from "./InMemoryMonitorsRepository.ts";
+import { InMemoryIncidentsRepository } from "./InMemoryIncidentsRepository.ts";
+import { createMockLogger } from "./createMockLogger.ts";
+import type { Monitor } from "../../src/types/monitor.ts";
+import type { MonitorStatusResponse } from "../../src/types/network.ts";
+import type { Check } from "../../src/types/check.ts";
+import type { MaintenanceWindow } from "../../src/types/maintenanceWindow.ts";
+
+let checkCounter = 0;
+
+export const makeMonitor = (overrides?: Partial<Monitor>): Monitor =>
+	({
+		id: "mon-1",
+		teamId: "team-1",
+		name: "Test Monitor",
+		type: "http",
+		url: "https://example.com",
+		status: "up",
+		// Pre-fill window so threshold evaluation runs immediately.
+		// Without this, the warm-up path sets monitor.status directly
+		// from each check, bypassing the threshold logic.
+		statusWindow: [true, true, true, true, true],
+		statusWindowSize: 5,
+		statusWindowThreshold: 60,
+		recentChecks: [],
+		notifications: [],
+		...overrides,
+	}) as Monitor;
+
+export const makeStatusResponse = (status: boolean, code: number): MonitorStatusResponse => ({
+	monitorId: "mon-1",
+	teamId: "team-1",
+	type: "http",
+	status,
+	code,
+	message: status ? "OK" : "Service Unavailable",
+	responseTime: status ? 150 : 0,
+});
+
+export const makeCheck = (status: boolean, code: number): Check => {
+	const now = new Date().toISOString();
+	return {
+		id: `check-${++checkCounter}`,
+		metadata: { monitorId: "mon-1", teamId: "team-1", type: "http" },
+		status,
+		statusCode: code,
+		responseTime: status ? 150 : 0,
+		message: status ? "OK" : "Service Unavailable",
+		createdAt: now,
+		updatedAt: now,
+	};
+};
+
+const createStubMonitorStatsRepo = () => ({
+	findByMonitorId: jest.fn().mockRejectedValue(new Error("no stats")),
+	create: jest.fn().mockResolvedValue({}),
+	updateByMonitorId: jest.fn().mockResolvedValue({}),
+	deleteByMonitorId: jest.fn(),
+	deleteByMonitorIds: jest.fn(),
+	deleteByMonitorIdsNotIn: jest.fn(),
+});
+
+const createStubChecksRepo = () => ({
+	create: jest.fn(),
+	createChecks: jest.fn(),
+	findByMonitorId: jest.fn(),
+	findByTeamId: jest.fn(),
+	findLatestByMonitorIds: jest.fn(),
+	findByDateRangeAndMonitorId: jest.fn(),
+	findSummaryByTeamId: jest.fn(),
+	deleteByMonitorId: jest.fn(),
+	deleteByTeamId: jest.fn(),
+	deleteByMonitorIdsNotIn: jest.fn(),
+	deleteOlderThan: jest.fn(),
+});
+
+export interface HeartbeatTestHarness {
+	monitorsRepo: InMemoryMonitorsRepository;
+	incidentsRepo: InMemoryIncidentsRepository;
+	statusService: StatusService;
+	incidentService: IncidentService;
+	notificationsService: { handleNotifications: jest.Mock };
+	networkService: { requestStatus: jest.Mock };
+	bufferStub: { addToBuffer: jest.Mock; addGeoCheckToBuffer: jest.Mock; scheduleNextFlush: jest.Mock };
+	maintenanceWindowsRepo: { findByMonitorId: jest.Mock };
+	messageBuilder: { extractThresholdBreaches: jest.Mock };
+	heartbeatJob: (monitor: Monitor) => Promise<void>;
+	setNextResponse: (status: boolean, code: number) => void;
+	setNextResponseFull: (response: MonitorStatusResponse) => void;
+}
+
+export function createHeartbeatTestHarness(): HeartbeatTestHarness {
+	checkCounter = 0;
+
+	const monitorsRepo = new InMemoryMonitorsRepository();
+	const incidentsRepo = new InMemoryIncidentsRepository();
+	const logger = createMockLogger() as any;
+	const bufferStub = { addToBuffer: jest.fn(), addGeoCheckToBuffer: jest.fn(), scheduleNextFlush: jest.fn() };
+
+	const statusService = new StatusService(
+		logger,
+		bufferStub as any,
+		monitorsRepo as any,
+		createStubMonitorStatsRepo() as any,
+		createStubChecksRepo() as any
+	);
+
+	const messageBuilder = { extractThresholdBreaches: jest.fn().mockReturnValue([]) };
+	const incidentService = new IncidentService(logger, incidentsRepo, monitorsRepo as any, { findById: jest.fn() } as any, messageBuilder as any);
+
+	const notificationsService = { handleNotifications: jest.fn().mockResolvedValue(true) };
+
+	let nextResponse: MonitorStatusResponse | null = null;
+	let nextStatus = true;
+	let nextCode = 200;
+	const networkService = {
+		requestStatus: jest.fn().mockImplementation(() => {
+			if (nextResponse) {
+				return Promise.resolve(nextResponse);
+			}
+			return Promise.resolve(makeStatusResponse(nextStatus, nextCode));
+		}),
+	};
+	const checkService = {
+		buildCheck: jest.fn().mockImplementation((response: MonitorStatusResponse) => {
+			return makeCheck(response.status, response.code);
+		}),
+	};
+
+	const setNextResponse = (status: boolean, code: number) => {
+		nextResponse = null;
+		nextStatus = status;
+		nextCode = code;
+	};
+
+	const setNextResponseFull = (response: MonitorStatusResponse) => {
+		nextResponse = response;
+	};
+
+	const maintenanceWindowsRepo = { findByMonitorId: jest.fn().mockResolvedValue([]) };
+
+	const helper = new SuperSimpleQueueHelper(
+		logger,
+		networkService as any,
+		statusService as any,
+		notificationsService as any,
+		checkService as any,
+		{ getDBSettings: jest.fn() } as any,
+		bufferStub as any,
+		incidentService as any,
+		maintenanceWindowsRepo as any,
+		monitorsRepo as any,
+		{ findAllTeamIds: jest.fn() } as any,
+		createStubMonitorStatsRepo() as any,
+		createStubChecksRepo() as any,
+		incidentsRepo as any,
+		{ buildGeoCheck: jest.fn() } as any,
+		{ deleteByMonitorIdsNotIn: jest.fn() } as any
+	);
+
+	return {
+		monitorsRepo,
+		incidentsRepo,
+		statusService,
+		incidentService,
+		notificationsService,
+		networkService,
+		bufferStub,
+		maintenanceWindowsRepo,
+		messageBuilder,
+		heartbeatJob: helper.getHeartbeatJob(),
+		setNextResponse,
+		setNextResponseFull,
+	};
+}
diff --git a/server/test/integration/heartbeatJobDownDetection.test.ts b/server/test/integration/heartbeatJobDownDetection.test.ts
new file mode 100644
index 000000000..abf928cb1
--- /dev/null
+++ b/server/test/integration/heartbeatJobDownDetection.test.ts
@@ -0,0 +1,76 @@
+import { describe, expect, it, beforeEach } from "@jest/globals";
+import { createHeartbeatTestHarness, makeMonitor, type HeartbeatTestHarness } from "../helpers/heartbeatTestHarness.ts";
+
+describe("Heartbeat job: down detection", () => {
+	let h: HeartbeatTestHarness;
+
+	beforeEach(() => {
+		h = createHeartbeatTestHarness();
+	});
+
+	it("transitions monitor to down and creates incident after threshold failures", async () => {
+		// Monitor starts with full passing window: [true, true, true, true, true]
+		const monitor = makeMonitor();
+		h.monitorsRepo.seed(monitor);
+
+		// 2 failures: window = [true, true, true, false, false] = 40% < 60%
+		h.setNextResponse(false, 503);
+		await h.heartbeatJob(monitor);
+		await h.heartbeatJob(monitor);
+
+		let storedMonitor = await h.monitorsRepo.findById("mon-1", "team-1");
+		expect(storedMonitor.status).toBe("up");
+		expect(h.incidentsRepo.getAll()).toHaveLength(0);
+
+		// 3rd failure: window = [true, true, false, false, false] = 60% >= 60%
+		await h.heartbeatJob(monitor);
+
+		storedMonitor = await h.monitorsRepo.findById("mon-1", "team-1");
+		expect(storedMonitor.status).toBe("down");
+
+		// Incident should have been created
+		const incidents = h.incidentsRepo.getAll();
+		expect(incidents).toHaveLength(1);
+		expect(incidents[0].monitorId).toBe("mon-1");
+		expect(incidents[0].status).toBe(true);
+		expect(incidents[0].statusCode).toBe(503);
+
+		// Notification should have been triggered
+		expect(h.notificationsService.handleNotifications).toHaveBeenCalled();
+	});
+
+	it("does not create duplicate incidents on continued failures", async () => {
+		const monitor = makeMonitor();
+		h.monitorsRepo.seed(monitor);
+
+		h.setNextResponse(false, 500);
+
+		// 3 failures trigger down, 4 more continue failing
+		for (let i = 0; i < 7; i++) {
+			await h.heartbeatJob(monitor);
+		}
+
+		// Only one incident despite 7 heartbeats
+		expect(h.incidentsRepo.getAll()).toHaveLength(1);
+	});
+
+	it("stays up when failures are below threshold", async () => {
+		const monitor = makeMonitor();
+		h.monitorsRepo.seed(monitor);
+
+		// 2 failures: window = [true, true, true, false, false] = 40% < 60%
+		h.setNextResponse(false, 500);
+		await h.heartbeatJob(monitor);
+		await h.heartbeatJob(monitor);
+
+		// 3 passes: window = [false, false, true, true, true] = 40% < 60%
+		h.setNextResponse(true, 200);
+		await h.heartbeatJob(monitor);
+		await h.heartbeatJob(monitor);
+		await h.heartbeatJob(monitor);
+
+		const storedMonitor = await h.monitorsRepo.findById("mon-1", "team-1");
+		expect(storedMonitor.status).toBe("up");
+		expect(h.incidentsRepo.getAll()).toHaveLength(0);
+	});
+});
diff --git a/server/test/integration/heartbeatJobMaintenance.test.ts b/server/test/integration/heartbeatJobMaintenance.test.ts
new file mode 100644
index 000000000..663c2e61e
--- /dev/null
+++ b/server/test/integration/heartbeatJobMaintenance.test.ts
@@ -0,0 +1,129 @@
+import { describe, expect, it, beforeEach } from "@jest/globals";
+import { createHeartbeatTestHarness, makeMonitor, type HeartbeatTestHarness } from "../helpers/heartbeatTestHarness.ts";
+import type { MaintenanceWindow } from "../../src/types/maintenanceWindow.ts";
+
+const makeMaintenanceWindow = (overrides?: Partial<MaintenanceWindow>): MaintenanceWindow => {
+	const now = new Date();
+	const start = new Date(now.getTime() - 60 * 60 * 1000); // 1 hour ago
+	const end = new Date(now.getTime() + 60 * 60 * 1000); // 1 hour from now
+	return {
+		id: "mw-1",
+		monitorId: "mon-1",
+		teamId: "team-1",
+		active: true,
+		name: "Test Maintenance",
+		duration: 2,
+		durationUnit: "hours",
+		repeat: 0,
+		start: start.toISOString(),
+		end: end.toISOString(),
+		createdAt: new Date().toISOString(),
+		updatedAt: new Date().toISOString(),
+		...overrides,
+	};
+};
+
+describe("Heartbeat job: maintenance windows", () => {
+	let h: HeartbeatTestHarness;
+
+	beforeEach(() => {
+		h = createHeartbeatTestHarness();
+	});
+
+	it("skips checks and sets monitor to maintenance when window is active", async () => {
+		const monitor = makeMonitor();
+		h.monitorsRepo.seed(monitor);
+
+		// Configure an active maintenance window covering the current time
+		h.maintenanceWindowsRepo.findByMonitorId.mockResolvedValue([makeMaintenanceWindow()]);
+
+		await h.heartbeatJob(monitor);
+
+		// Monitor status should be set to maintenance
+		const storedMonitor = await h.monitorsRepo.findById("mon-1", "team-1");
+		expect(storedMonitor.status).toBe("maintenance");
+
+		// No network request should have been made
+		expect(h.networkService.requestStatus).not.toHaveBeenCalled();
+
+		// No check should have been buffered
+		expect(h.bufferStub.addToBuffer).not.toHaveBeenCalled();
+
+		// No incident should have been created
+		expect(h.incidentsRepo.getAll()).toHaveLength(0);
+
+		// No notification should have been sent
+		expect(h.notificationsService.handleNotifications).not.toHaveBeenCalled();
+	});
+
+	it("does not update status if monitor is already in maintenance", async () => {
+		const monitor = makeMonitor({ status: "maintenance" });
+		h.monitorsRepo.seed(monitor);
+
+		h.maintenanceWindowsRepo.findByMonitorId.mockResolvedValue([makeMaintenanceWindow()]);
+
+		await h.heartbeatJob(monitor);
+
+		// findById reads the stored monitor; updateById should not have been called
+		// since status was already "maintenance"
+		const storedMonitor = await h.monitorsRepo.findById("mon-1", "team-1");
+		expect(storedMonitor.status).toBe("maintenance");
+		expect(h.networkService.requestStatus).not.toHaveBeenCalled();
+	});
+
+	it("resumes normal checks when maintenance window expires", async () => {
+		const monitor = makeMonitor();
+		h.monitorsRepo.seed(monitor);
+
+		// First heartbeat: inside maintenance window
+		h.maintenanceWindowsRepo.findByMonitorId.mockResolvedValue([makeMaintenanceWindow()]);
+		await h.heartbeatJob(monitor);
+
+		let storedMonitor = await h.monitorsRepo.findById("mon-1", "team-1");
+		expect(storedMonitor.status).toBe("maintenance");
+
+		// Second heartbeat: maintenance window expired (no windows returned)
+		h.maintenanceWindowsRepo.findByMonitorId.mockResolvedValue([]);
+		h.setNextResponse(true, 200);
+		await h.heartbeatJob(monitor);
+
+		// Network request should have been made this time
+		expect(h.networkService.requestStatus).toHaveBeenCalledTimes(1);
+
+		// Check should have been buffered
+		expect(h.bufferStub.addToBuffer).toHaveBeenCalledTimes(1);
+	});
+
+	it("skips checks when window is inactive (active: false)", async () => {
+		const monitor = makeMonitor();
+		h.monitorsRepo.seed(monitor);
+
+		// Inactive maintenance window — should be ignored
+		h.maintenanceWindowsRepo.findByMonitorId.mockResolvedValue([makeMaintenanceWindow({ active: false })]);
+
+		h.setNextResponse(true, 200);
+		await h.heartbeatJob(monitor);
+
+		// Normal check should proceed since window is inactive
+		expect(h.networkService.requestStatus).toHaveBeenCalledTimes(1);
+		expect(h.bufferStub.addToBuffer).toHaveBeenCalledTimes(1);
+	});
+
+	it("skips checks when window is in the past (expired)", async () => {
+		const monitor = makeMonitor();
+		h.monitorsRepo.seed(monitor);
+
+		// Window ended an hour ago
+		const pastEnd = new Date(Date.now() - 60 * 60 * 1000);
+		const pastStart = new Date(pastEnd.getTime() - 2 * 60 * 60 * 1000);
+		h.maintenanceWindowsRepo.findByMonitorId.mockResolvedValue([
+			makeMaintenanceWindow({ start: pastStart.toISOString(), end: pastEnd.toISOString() }),
+		]);
+
+		h.setNextResponse(true, 200);
+		await h.heartbeatJob(monitor);
+
+		// Window is in the past — normal check should proceed
+		expect(h.networkService.requestStatus).toHaveBeenCalledTimes(1);
+	});
+});
diff --git a/server/test/integration/heartbeatJobNotificationFailure.test.ts b/server/test/integration/heartbeatJobNotificationFailure.test.ts
new file mode 100644
index 000000000..bb231aa71
--- /dev/null
+++ b/server/test/integration/heartbeatJobNotificationFailure.test.ts
@@ -0,0 +1,61 @@
+import { describe, expect, it, beforeEach } from "@jest/globals";
+import { createHeartbeatTestHarness, makeMonitor, type HeartbeatTestHarness } from "../helpers/heartbeatTestHarness.ts";
+
+describe("Heartbeat job: notification failure isolation", () => {
+	let h: HeartbeatTestHarness;
+
+	beforeEach(() => {
+		h = createHeartbeatTestHarness();
+	});
+
+	it("creates incident even when notification dispatch throws", async () => {
+		const monitor = makeMonitor();
+		h.monitorsRepo.seed(monitor);
+
+		// Make notifications throw
+		h.notificationsService.handleNotifications.mockRejectedValue(new Error("SMTP connection refused"));
+
+		// Drive monitor down
+		h.setNextResponse(false, 503);
+		for (let i = 0; i < 3; i++) {
+			await h.heartbeatJob(monitor);
+		}
+
+		// Incident should still have been created
+		const incidents = h.incidentsRepo.getAll();
+		expect(incidents).toHaveLength(1);
+		expect(incidents[0].status).toBe(true);
+		expect(incidents[0].statusCode).toBe(503);
+
+		// Monitor should still be marked down
+		const storedMonitor = await h.monitorsRepo.findById("mon-1", "team-1");
+		expect(storedMonitor.status).toBe("down");
+	});
+
+	it("auto-resolves incident even when recovery notification throws", async () => {
+		const monitor = makeMonitor();
+		h.monitorsRepo.seed(monitor);
+
+		// Drive monitor down (notifications succeed here)
+		h.setNextResponse(false, 503);
+		for (let i = 0; i < 3; i++) {
+			await h.heartbeatJob(monitor);
+		}
+		expect(h.incidentsRepo.getAll()[0].status).toBe(true);
+
+		// Now make notifications throw for the recovery
+		h.notificationsService.handleNotifications.mockRejectedValue(new Error("Slack API timeout"));
+
+		// Recover
+		h.setNextResponse(true, 200);
+		for (let i = 0; i < 5; i++) {
+			await h.heartbeatJob(monitor);
+		}
+
+		// Incident should still be resolved despite notification failure
+		const incidents = h.incidentsRepo.getAll();
+		expect(incidents).toHaveLength(1);
+		expect(incidents[0].status).toBe(false);
+		expect(incidents[0].resolutionType).toBe("automatic");
+	});
+});
diff --git a/server/test/integration/heartbeatJobRecovery.test.ts b/server/test/integration/heartbeatJobRecovery.test.ts
new file mode 100644
index 000000000..10b6a32ca
--- /dev/null
+++ b/server/test/integration/heartbeatJobRecovery.test.ts
@@ -0,0 +1,77 @@
+import { describe, expect, it, beforeEach } from "@jest/globals";
+import { createHeartbeatTestHarness, makeMonitor, type HeartbeatTestHarness } from "../helpers/heartbeatTestHarness.ts";
+
+describe("Heartbeat job: recovery", () => {
+	let h: HeartbeatTestHarness;
+
+	beforeEach(() => {
+		h = createHeartbeatTestHarness();
+	});
+
+	it("recovers monitor and auto-resolves incident when checks pass", async () => {
+		const monitor = makeMonitor();
+		h.monitorsRepo.seed(monitor);
+
+		// 3 failures to trigger down (60% threshold)
+		h.setNextResponse(false, 503);
+		for (let i = 0; i < 3; i++) {
+			await h.heartbeatJob(monitor);
+		}
+		expect(h.incidentsRepo.getAll()).toHaveLength(1);
+		expect(h.incidentsRepo.getAll()[0].status).toBe(true);
+
+		// Send passing checks to push failure rate below threshold
+		// Window after 3 fails: [false, false, false, false, false] (prior trues shifted out)
+		// Need enough passes to drop below 60%
+		h.setNextResponse(true, 200);
+		for (let i = 0; i < 5; i++) {
+			await h.heartbeatJob(monitor);
+		}
+
+		// Monitor should be back up
+		const storedMonitor = await h.monitorsRepo.findById("mon-1", "team-1");
+		expect(storedMonitor.status).toBe("up");
+
+		// Incident should be auto-resolved
+		const incidents = h.incidentsRepo.getAll();
+		expect(incidents).toHaveLength(1);
+		expect(incidents[0].status).toBe(false);
+		expect(incidents[0].resolutionType).toBe("automatic");
+		expect(incidents[0].endTime).not.toBeNull();
+	});
+
+	it("creates a new incident after recovery if monitor goes down again", async () => {
+		const monitor = makeMonitor();
+		h.monitorsRepo.seed(monitor);
+
+		// First outage: 3 failures to trigger (window shifts from all-true)
+		h.setNextResponse(false, 503);
+		for (let i = 0; i < 3; i++) {
+			await h.heartbeatJob(monitor);
+		}
+
+		// Recovery: enough passes to drop below threshold
+		h.setNextResponse(true, 200);
+		for (let i = 0; i < 5; i++) {
+			await h.heartbeatJob(monitor);
+		}
+
+		// Second outage: 3 more failures to trigger again
+		h.setNextResponse(false, 502);
+		for (let i = 0; i < 3; i++) {
+			await h.heartbeatJob(monitor);
+		}
+
+		const incidents = h.incidentsRepo.getAll();
+		expect(incidents).toHaveLength(2);
+
+		// First incident resolved
+		expect(incidents[0].status).toBe(false);
+		expect(incidents[0].resolutionType).toBe("automatic");
+		expect(incidents[0].statusCode).toBe(503);
+
+		// Second incident active
+		expect(incidents[1].status).toBe(true);
+		expect(incidents[1].statusCode).toBe(502);
+	});
+});
diff --git a/server/test/integration/heartbeatJobThresholdBreach.test.ts b/server/test/integration/heartbeatJobThresholdBreach.test.ts
new file mode 100644
index 000000000..edaf63173
--- /dev/null
+++ b/server/test/integration/heartbeatJobThresholdBreach.test.ts
@@ -0,0 +1,153 @@
+import { describe, expect, it, beforeEach } from "@jest/globals";
+import { createHeartbeatTestHarness, makeMonitor, type HeartbeatTestHarness } from "../helpers/heartbeatTestHarness.ts";
+import type { MonitorStatusResponse } from "../../src/types/network.ts";
+import type { HardwareStatusPayload } from "../../src/types/network.ts";
+
+const makeHardwareResponse = (cpuUsage: number): MonitorStatusResponse<HardwareStatusPayload> => ({
+	monitorId: "mon-1",
+	teamId: "team-1",
+	type: "hardware",
+	status: true,
+	code: 200,
+	message: "OK",
+	responseTime: 50,
+	payload: {
+		data: {
+			cpu: { usage_percent: cpuUsage, temperature: [] },
+			memory: { usage_percent: 0.3 },
+			disk: [{ usage_percent: 0.2 }],
+		},
+	},
+});
+
+describe("Heartbeat job: hardware threshold breach", () => {
+	let h: HeartbeatTestHarness;
+
+	beforeEach(() => {
+		h = createHeartbeatTestHarness();
+	});
+
+	it("transitions to breached and creates incident after alert counter hits zero", async () => {
+		// Hardware monitor with CPU threshold at 80% (stored as 80, compared as 80/100 = 0.8)
+		// Alert counters start at 5, decrement each breach, trigger at 0
+		const monitor = makeMonitor({
+			type: "hardware",
+			status: "up",
+			cpuAlertThreshold: 80,
+			cpuAlertCounter: 5,
+			memoryAlertThreshold: 100,
+			memoryAlertCounter: 5,
+			diskAlertThreshold: 100,
+			diskAlertCounter: 5,
+			tempAlertThreshold: 100,
+			tempAlertCounter: 5,
+			selectedDisks: [],
+		});
+		h.monitorsRepo.seed(monitor);
+
+		// CPU at 90% (0.9) exceeds threshold of 80% (0.8)
+		h.setNextResponseFull(makeHardwareResponse(0.9));
+
+		// Configure message builder for when incident is created
+		h.messageBuilder.extractThresholdBreaches.mockReturnValue([{ metric: "cpu", formattedValue: "90%", threshold: 80, unit: "%" }]);
+
+		// 4 heartbeats: counter goes 5→4→3→2→1, status still "up"
+		for (let i = 0; i < 4; i++) {
+			await h.heartbeatJob(monitor);
+		}
+
+		let storedMonitor = await h.monitorsRepo.findById("mon-1", "team-1");
+		expect(storedMonitor.status).toBe("up");
+		expect(storedMonitor.cpuAlertCounter).toBe(1);
+		expect(h.incidentsRepo.getAll()).toHaveLength(0);
+
+		// 5th heartbeat: counter hits 0, status transitions to "breached"
+		await h.heartbeatJob(monitor);
+
+		storedMonitor = await h.monitorsRepo.findById("mon-1", "team-1");
+		expect(storedMonitor.status).toBe("breached");
+		expect(storedMonitor.cpuAlertCounter).toBe(0);
+
+		// Incident created with statusCode 9999 and threshold message
+		const incidents = h.incidentsRepo.getAll();
+		expect(incidents).toHaveLength(1);
+		expect(incidents[0].statusCode).toBe(9999);
+		expect(incidents[0].message).toBe("CPU: 90% (threshold: 80%)");
+		expect(incidents[0].status).toBe(true);
+
+		// Notification should have been triggered
+		expect(h.notificationsService.handleNotifications).toHaveBeenCalled();
+	});
+
+	it("recovers from breached to up when metrics return to normal", async () => {
+		// Start with a monitor already in breached state with counter at 0
+		const monitor = makeMonitor({
+			type: "hardware",
+			status: "breached",
+			cpuAlertThreshold: 80,
+			cpuAlertCounter: 0,
+			memoryAlertThreshold: 100,
+			memoryAlertCounter: 5,
+			diskAlertThreshold: 100,
+			diskAlertCounter: 5,
+			tempAlertThreshold: 100,
+			tempAlertCounter: 5,
+			selectedDisks: [],
+		});
+		h.monitorsRepo.seed(monitor);
+
+		// Also seed an active incident for this monitor
+		await h.incidentsRepo.create({
+			monitorId: "mon-1",
+			teamId: "team-1",
+			status: true,
+			statusCode: 9999,
+			message: "CPU: 90% (threshold: 80%)",
+		});
+
+		// CPU at 50% (0.5) — below threshold of 80% (0.8)
+		h.setNextResponseFull(makeHardwareResponse(0.5));
+
+		await h.heartbeatJob(monitor);
+
+		// Monitor should recover to "up"
+		const storedMonitor = await h.monitorsRepo.findById("mon-1", "team-1");
+		expect(storedMonitor.status).toBe("up");
+		// Counter resets to 5 when not breaching
+		expect(storedMonitor.cpuAlertCounter).toBe(5);
+
+		// Incident should be auto-resolved
+		const incidents = h.incidentsRepo.getAll();
+		expect(incidents).toHaveLength(1);
+		expect(incidents[0].status).toBe(false);
+		expect(incidents[0].resolutionType).toBe("automatic");
+	});
+
+	it("does not create duplicate incidents while remaining breached", async () => {
+		const monitor = makeMonitor({
+			type: "hardware",
+			status: "up",
+			cpuAlertThreshold: 80,
+			cpuAlertCounter: 5,
+			memoryAlertThreshold: 100,
+			memoryAlertCounter: 5,
+			diskAlertThreshold: 100,
+			diskAlertCounter: 5,
+			tempAlertThreshold: 100,
+			tempAlertCounter: 5,
+			selectedDisks: [],
+		});
+		h.monitorsRepo.seed(monitor);
+
+		h.setNextResponseFull(makeHardwareResponse(0.9));
+		h.messageBuilder.extractThresholdBreaches.mockReturnValue([{ metric: "cpu", formattedValue: "90%", threshold: 80, unit: "%" }]);
+
+		// 5 heartbeats to trigger breach, then 5 more while still breaching
+		for (let i = 0; i < 10; i++) {
+			await h.heartbeatJob(monitor);
+		}
+
+		// Only one incident despite 10 heartbeats
+		expect(h.incidentsRepo.getAll()).toHaveLength(1);
+	});
+});
diff --git a/server/test/integration/incidentLifecycle.test.ts b/server/test/integration/incidentLifecycle.test.ts
new file mode 100644
index 000000000..d2429a812
--- /dev/null
+++ b/server/test/integration/incidentLifecycle.test.ts
@@ -0,0 +1,216 @@
+import { describe, expect, it, jest, beforeEach } from "@jest/globals";
+import { IncidentService } from "../../src/service/business/incidentService.ts";
+import { InMemoryIncidentsRepository } from "../helpers/InMemoryIncidentsRepository.ts";
+import { createMockLogger } from "../helpers/createMockLogger.ts";
+import type { IMonitorsRepository, IUsersRepository } from "../../src/repositories/index.ts";
+import type { INotificationMessageBuilder } from "../../src/service/infrastructure/notificationMessageBuilder.ts";
+import type { Monitor } from "../../src/types/monitor.ts";
+import type { MonitorActionDecision } from "../../src/service/infrastructure/SuperSimpleQueue/SuperSimpleQueueHelper.ts";
+
+// ── Helpers ──────────────────────────────────────────────────────────────────
+
+const makeMonitor = (overrides?: Partial<Monitor>): Monitor =>
+	({
+		id: "mon-1",
+		teamId: "team-1",
+		name: "Test Monitor",
+		type: "http",
+		url: "https://example.com",
+		status: "down",
+		...overrides,
+	}) as Monitor;
+
+const makeDecision = (overrides?: Partial<MonitorActionDecision>): MonitorActionDecision => ({
+	shouldCreateIncident: false,
+	shouldResolveIncident: false,
+	shouldSendNotification: false,
+	incidentReason: null,
+	notificationReason: null,
+	...overrides,
+});
+
+// ── Test suite ───────────────────────────────────────────────────────────────
+
+describe("Incident lifecycle (integration)", () => {
+	let repo: InMemoryIncidentsRepository;
+	let service: IncidentService;
+	let monitorsRepo: jest.Mocked<IMonitorsRepository>;
+	let usersRepo: jest.Mocked<IUsersRepository>;
+	let messageBuilder: jest.Mocked<INotificationMessageBuilder>;
+
+	beforeEach(() => {
+		repo = new InMemoryIncidentsRepository();
+		monitorsRepo = { findById: jest.fn() } as unknown as jest.Mocked<IMonitorsRepository>;
+		usersRepo = { findById: jest.fn() } as unknown as jest.Mocked<IUsersRepository>;
+		messageBuilder = { extractThresholdBreaches: jest.fn() } as unknown as jest.Mocked<INotificationMessageBuilder>;
+		service = new IncidentService(createMockLogger() as any, repo, monitorsRepo, usersRepo, messageBuilder);
+	});
+
+	// ── Creation ─────────────────────────────────────────────────────────────
+
+	it("creates an incident when monitor goes down", async () => {
+		const monitor = makeMonitor({ status: "down" });
+		const decision = makeDecision({ shouldCreateIncident: true, incidentReason: "status_down" });
+
+		const incident = await service.handleIncident(monitor, 503, decision);
+
+		expect(incident).not.toBeNull();
+		expect(incident!.monitorId).toBe("mon-1");
+		expect(incident!.teamId).toBe("team-1");
+		expect(incident!.status).toBe(true);
+		expect(incident!.statusCode).toBe(503);
+		expect(incident!.endTime).toBeNull();
+		expect(incident!.resolutionType).toBeNull();
+
+		const stored = repo.getAll();
+		expect(stored).toHaveLength(1);
+		expect(stored[0].id).toBe(incident!.id);
+	});
+
+	// ── Idempotency ──────────────────────────────────────────────────────────
+
+	it("does not create a duplicate incident for the same monitor", async () => {
+		const monitor = makeMonitor({ status: "down" });
+		const decision = makeDecision({ shouldCreateIncident: true, incidentReason: "status_down" });
+
+		const first = await service.handleIncident(monitor, 503, decision);
+		const second = await service.handleIncident(monitor, 503, decision);
+
+		expect(second!.id).toBe(first!.id);
+		expect(repo.getAll()).toHaveLength(1);
+	});
+
+	// ── Auto-resolve ─────────────────────────────────────────────────────────
+
+	it("auto-resolves an incident when monitor recovers", async () => {
+		const monitor = makeMonitor({ status: "down" });
+		const createDecision = makeDecision({ shouldCreateIncident: true, incidentReason: "status_down" });
+		const created = await service.handleIncident(monitor, 503, createDecision);
+
+		const resolveDecision = makeDecision({ shouldResolveIncident: true });
+		const resolved = await service.handleIncident(monitor, 200, resolveDecision);
+
+		expect(resolved).not.toBeNull();
+		expect(resolved!.id).toBe(created!.id);
+		expect(resolved!.status).toBe(false);
+		expect(resolved!.endTime).toBeDefined();
+		expect(resolved!.resolutionType).toBe("automatic");
+	});
+
+	// ── Resolve with nothing active ──────────────────────────────────────────
+
+	it("returns null when resolving with no active incident", async () => {
+		const monitor = makeMonitor({ status: "up" });
+		const decision = makeDecision({ shouldResolveIncident: true });
+
+		const result = await service.handleIncident(monitor, 200, decision);
+
+		expect(result).toBeNull();
+	});
+
+	// ── Manual resolution ────────────────────────────────────────────────────
+
+	it("manually resolves an active incident with comment", async () => {
+		const monitor = makeMonitor({ status: "down" });
+		const decision = makeDecision({ shouldCreateIncident: true, incidentReason: "status_down" });
+		const created = await service.handleIncident(monitor, 500, decision);
+
+		const resolved = await service.resolveIncident(created!.id, "user-1", "team-1", "Root cause identified", "user@test.com");
+
+		expect(resolved.status).toBe(false);
+		expect(resolved.resolutionType).toBe("manual");
+		expect(resolved.resolvedBy).toBe("user-1");
+		expect(resolved.resolvedByEmail).toBe("user@test.com");
+		expect(resolved.comment).toBe("Root cause identified");
+		expect(resolved.endTime).toBeDefined();
+	});
+
+	it("throws when manually resolving an already-resolved incident", async () => {
+		const monitor = makeMonitor({ status: "down" });
+		const decision = makeDecision({ shouldCreateIncident: true, incidentReason: "status_down" });
+		const created = await service.handleIncident(monitor, 500, decision);
+
+		await service.resolveIncident(created!.id, "user-1", "team-1");
+
+		await expect(service.resolveIncident(created!.id, "user-1", "team-1")).rejects.toThrow("Incident not found");
+	});
+
+	// ── Threshold breach ─────────────────────────────────────────────────────
+
+	it("creates a threshold breach incident with statusCode 9999 and descriptive message", async () => {
+		const monitor = makeMonitor({ status: "breached", type: "hardware" });
+		(messageBuilder.extractThresholdBreaches as jest.Mock).mockReturnValue([
+			{ metric: "cpu", formattedValue: "92%", threshold: 80, unit: "%" },
+			{ metric: "memory", formattedValue: "88%", threshold: 85, unit: "%" },
+		]);
+		const decision = makeDecision({ shouldCreateIncident: true, incidentReason: "threshold_breach" });
+
+		const incident = await service.handleIncident(monitor, 200, decision, { monitorId: "mon-1" } as any);
+
+		expect(incident!.statusCode).toBe(9999);
+		expect(incident!.message).toBe("CPU: 92% (threshold: 80%), MEMORY: 88% (threshold: 85%)");
+	});
+
+	// ── No action ────────────────────────────────────────────────────────────
+
+	it("returns null when no action is needed", async () => {
+		const monitor = makeMonitor({ status: "up" });
+		const decision = makeDecision();
+
+		const result = await service.handleIncident(monitor, 200, decision);
+
+		expect(result).toBeNull();
+		expect(repo.getAll()).toHaveLength(0);
+	});
+
+	// ── Full lifecycle ───────────────────────────────────────────────────────
+
+	it("handles a complete lifecycle: create -> manual resolve -> new incident -> auto-resolve", async () => {
+		const monitor = makeMonitor({ status: "down" });
+
+		// First outage
+		const first = await service.handleIncident(monitor, 503, makeDecision({ shouldCreateIncident: true, incidentReason: "status_down" }));
+		expect(first!.status).toBe(true);
+
+		// Manually resolved
+		await service.resolveIncident(first!.id, "user-1", "team-1", "Restarted server");
+
+		// Second outage — new incident since previous was resolved
+		const second = await service.handleIncident(monitor, 502, makeDecision({ shouldCreateIncident: true, incidentReason: "status_down" }));
+		expect(second!.id).not.toBe(first!.id);
+		expect(second!.statusCode).toBe(502);
+
+		// Auto-resolve
+		const resolved = await service.handleIncident(monitor, 200, makeDecision({ shouldResolveIncident: true }));
+		expect(resolved!.id).toBe(second!.id);
+		expect(resolved!.status).toBe(false);
+		expect(resolved!.resolutionType).toBe("automatic");
+
+		// Both incidents stored, both resolved
+		const all = repo.getAll();
+		expect(all).toHaveLength(2);
+		expect(all.every((i) => i.status === false)).toBe(true);
+	});
+
+	// ── Cross-monitor isolation ──────────────────────────────────────────────
+
+	it("incidents for different monitors do not interfere", async () => {
+		const monitorA = makeMonitor({ id: "mon-a", status: "down" });
+		const monitorB = makeMonitor({ id: "mon-b", status: "down" });
+		const decision = makeDecision({ shouldCreateIncident: true, incidentReason: "status_down" });
+
+		const incidentA = await service.handleIncident(monitorA, 500, decision);
+		const incidentB = await service.handleIncident(monitorB, 502, decision);
+
+		expect(incidentA!.id).not.toBe(incidentB!.id);
+		expect(repo.getAll()).toHaveLength(2);
+
+		// Resolving monitor A does not affect monitor B
+		const resolved = await service.handleIncident(monitorA, 200, makeDecision({ shouldResolveIncident: true }));
+		expect(resolved!.id).toBe(incidentA!.id);
+
+		const bStillActive = await repo.findActiveByMonitorId("mon-b", "team-1");
+		expect(bStillActive).not.toBeNull();
+		expect(bStillActive!.status).toBe(true);
+	});
+});