diff --git a/package-lock.json b/package-lock.json
index a5816dea..e12dfb34 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -592,21 +592,21 @@
       "integrity": "sha512-tHq6qdbT9U1IRSGf14CL0pUlULksvY9OZ+5eEgl1N7t+OA3tGvNpxJCzuKQlsNgCVwbAs670L1vcVQi8j9HjnA==",
       "dev": true
     },
-    "@types/mkdirp": {
-      "version": "0.5.2",
-      "resolved": "https://registry.npmjs.org/@types/mkdirp/-/mkdirp-0.5.2.tgz",
-      "integrity": "sha512-U5icWpv7YnZYGsN4/cmh3WD2onMY0aJIiTE6+51TwJCttdHvtCYmkBNOobHlXwrJRL0nkH9jH4kD+1FAdMN4Tg==",
-      "dev": true,
-      "requires": {
-        "@types/node": "*"
-      }
-    },
     "@types/mocha": {
       "version": "5.2.7",
       "resolved": "https://registry.npmjs.org/@types/mocha/-/mocha-5.2.7.tgz",
       "integrity": "sha512-NYrtPht0wGzhwe9+/idPaBB+TqkY9AhTvOLMkThm0IoEfLaiVQZwBwyJ5puCkO3AUCWrmcoePjp2mbFocKy4SQ==",
       "dev": true
     },
+    "@types/mock-fs": {
+      "version": "4.13.0",
+      "resolved": "https://registry.npmjs.org/@types/mock-fs/-/mock-fs-4.13.0.tgz",
+      "integrity": "sha512-FUqxhURwqFtFBCuUj3uQMp7rPSQs//b3O9XecAVxhqS9y4/W8SIJEZFq2mmpnFVZBXwR/2OyPLE97CpyYiB8Mw==",
+      "dev": true,
+      "requires": {
+        "@types/node": "*"
+      }
+    },
     "@types/morgan": {
       "version": "1.9.0",
       "resolved": "https://registry.npmjs.org/@types/morgan/-/morgan-1.9.0.tgz",
@@ -1569,12 +1569,21 @@
       }
     },
     "blinking": {
-      "version": "0.0.3",
-      "resolved": "https://registry.npmjs.org/blinking/-/blinking-0.0.3.tgz",
-      "integrity": "sha1-c6LX+J2z2lSzYFxJiqXYYGv8Hnc=",
+      "version": "0.0.4",
+      "resolved": "https://registry.npmjs.org/blinking/-/blinking-0.0.4.tgz",
+      "integrity": "sha512-kIC2FbDXmd9ydtCYQjrSEpw/jpvqNKfn+uDSO03sLyEju9Q/ZZyJqvdB/sSSGsyzx3bc5J4MmcqvOY/iL7OgnA==",
       "dev": true,
       "requires": {
+        "@types/bluebird": "^3.5.33",
         "bluebird": "^3.0.0"
+      },
+      "dependencies": {
+        "@types/bluebird": {
+          "version": "3.5.33",
+          "resolved": "https://registry.npmjs.org/@types/bluebird/-/bluebird-3.5.33.tgz",
+          "integrity": "sha512-ndEo1xvnYeHxm7I/5sF6tBvnsA4Tdi3zj1keRKRs12SP+2ye2A27NDJ1B6PqkfMbGAcT+mqQVqbZRIrhfOp5PQ==",
+          "dev": true
+        }
       }
     },
     "bluebird": {
@@ -7062,6 +7071,12 @@
         }
       }
     },
+    "mock-fs": {
+      "version": "4.14.0",
+      "resolved": "https://registry.npmjs.org/mock-fs/-/mock-fs-4.14.0.tgz",
+      "integrity": "sha512-qYvlv/exQ4+svI3UOvPUpLDF0OMX5euvUH0Ny4N5QyRyhNdgAgUrVH3iUINSzEPLvx0kbo/Bp28GJKIqvE7URw==",
+      "dev": true
+    },
     "morgan": {
       "version": "1.10.0",
       "resolved": "https://registry.npmjs.org/morgan/-/morgan-1.10.0.tgz",
diff --git a/package.json b/package.json
index 907fbbc5..a0aa70e1 100644
--- a/package.json
+++ b/package.json
@@ -55,10 +55,9 @@
     "@types/lockfile": "^1.0.1",
     "@types/lodash": "^4.14.159",
     "@types/memoizee": "^0.4.4",
-    "@types/mkdirp": "^0.5.2",
     "@types/mocha": "^5.2.7",
+    "@types/mock-fs": "^4.13.0",
     "@types/morgan": "^1.9.0",
-    "@types/mz": "0.0.32",
     "@types/node": "^12.12.54",
     "@types/request": "^2.48.5",
     "@types/rewire": "^2.5.28",
@@ -74,9 +73,8 @@
     "@types/webpack": "^4.41.21",
     "@types/yargs": "^15.0.12",
     "balena-register-device": "^6.1.6",
-    "blinking": "~0.0.3",
+    "blinking": "^0.0.4",
     "bluebird": "^3.7.2",
-    "body-parser": "^1.19.0",
     "chai-as-promised": "^7.1.1",
     "chai-events": "0.0.1",
     "chai-like": "^1.1.1",
@@ -105,10 +103,9 @@
     "lodash": "^4.17.20",
     "memoizee": "^0.4.14",
     "mixpanel": "^0.10.3",
-    "mkdirp": "^0.5.5",
     "mocha": "^5.2.0",
+    "mock-fs": "^4.14.0",
     "morgan": "^1.10.0",
-    "mz": "^2.7.0",
     "network-checker": "^0.1.1",
     "nodemon": "^2.0.4",
     "pinejs-client-request": "^7.2.1",
diff --git a/src/api-binder.ts b/src/api-binder.ts
index e164baee..032f0633 100644
--- a/src/api-binder.ts
+++ b/src/api-binder.ts
@@ -1,5 +1,4 @@
 import * as Bluebird from 'bluebird';
-import * as bodyParser from 'body-parser';
 import { stripIndent } from 'common-tags';
 import * as express from 'express';
 import { isLeft } from 'fp-ts/lib/Either';
@@ -578,8 +577,8 @@ export const initialized = (async () => {
 })();
 
 export const router = express.Router();
-router.use(bodyParser.urlencoded({ limit: '10mb', extended: true }));
-router.use(bodyParser.json({ limit: '10mb' }));
+router.use(express.urlencoded({ limit: '10mb', extended: true }));
+router.use(express.json({ limit: '10mb' }));
 
 router.post('/v1/update', (req, res, next) => {
 	eventTracker.track('Update notification');
diff --git a/src/compose/application-manager.ts b/src/compose/application-manager.ts
index 1073a20c..212bed89 100644
--- a/src/compose/application-manager.ts
+++ b/src/compose/application-manager.ts
@@ -1,4 +1,3 @@
-import * as bodyParser from 'body-parser';
 import * as express from 'express';
 import * as _ from 'lodash';
 
@@ -61,8 +60,8 @@ const localModeManager = new LocalModeManager();
 
 export const router = (() => {
 	const $router = express.Router();
-	$router.use(bodyParser.urlencoded({ extended: true, limit: '10mb' }));
-	$router.use(bodyParser.json({ limit: '10mb' }));
+	$router.use(express.urlencoded({ extended: true, limit: '10mb' }));
+	$router.use(express.json({ limit: '10mb' }));
 
 	createV1Api($router);
 	createV2Api($router);
diff --git a/src/compose/network-manager.ts b/src/compose/network-manager.ts
index 3fa52988..6298fb2a 100644
--- a/src/compose/network-manager.ts
+++ b/src/compose/network-manager.ts
@@ -1,15 +1,15 @@
 import * as Bluebird from 'bluebird';
 import * as _ from 'lodash';
-import { fs } from 'mz';
 
 import * as constants from '../lib/constants';
 import { docker } from '../lib/docker-utils';
-import { ENOENT, NotFoundError } from '../lib/errors';
+import { NotFoundError } from '../lib/errors';
 import logTypes = require('../lib/log-types');
+import log from '../lib/supervisor-console';
+import { exists } from '../lib/fs-utils';
+
 import * as logger from '../logger';
 import { Network } from './network';
-
-import log from '../lib/supervisor-console';
 import { ResourceRecreationAttemptError } from './errors';
 
 export function getAll(): Bluebird<Network[]> {
@@ -69,23 +69,22 @@ export async function remove(network: Network) {
 	await network.remove();
 }
 
-export function supervisorNetworkReady(): Bluebird<boolean> {
-	return Bluebird.resolve(
-		fs.stat(`/sys/class/net/${constants.supervisorNetworkInterface}`),
-	)
-		.then(() => {
-			return docker.getNetwork(constants.supervisorNetworkInterface).inspect();
-		})
-		.then((network) => {
-			return (
-				network.Options['com.docker.network.bridge.name'] ===
-					constants.supervisorNetworkInterface &&
-				network.IPAM.Config[0].Subnet === constants.supervisorNetworkSubnet &&
-				network.IPAM.Config[0].Gateway === constants.supervisorNetworkGateway
-			);
-		})
-		.catchReturn(NotFoundError, false)
-		.catchReturn(ENOENT, false);
+export async function supervisorNetworkReady(): Promise<boolean> {
+	const networkExists = exists(
+		`/sys/class/net/${constants.supervisorNetworkInterface}`,
+	);
+	if (!networkExists) {
+		return false;
+	}
+	const network = await docker
+		.getNetwork(constants.supervisorNetworkInterface)
+		.inspect();
+	return (
+		network.Options['com.docker.network.bridge.name'] ===
+			constants.supervisorNetworkInterface &&
+		network.IPAM.Config[0].Subnet === constants.supervisorNetworkSubnet &&
+		network.IPAM.Config[0].Gateway === constants.supervisorNetworkGateway
+	);
 }
 
 export function ensureSupervisorNetwork(): Bluebird<void> {
@@ -109,11 +108,13 @@ export function ensureSupervisorNetwork(): Bluebird<void> {
 			) {
 				return removeIt();
 			} else {
-				return Bluebird.resolve(
-					fs.stat(`/sys/class/net/${constants.supervisorNetworkInterface}`),
-				)
-					.catch(ENOENT, removeIt)
-					.return();
+				return exists(
+					`/sys/class/net/${constants.supervisorNetworkInterface}`,
+				).then((networkExists) => {
+					if (!networkExists) {
+						return removeIt();
+					}
+				});
 			}
 		})
 		.catch(NotFoundError, () => {
diff --git a/src/compose/service-manager.ts b/src/compose/service-manager.ts
index d3aa8911..c46fc130 100644
--- a/src/compose/service-manager.ts
+++ b/src/compose/service-manager.ts
@@ -4,7 +4,7 @@ import { EventEmitter } from 'events';
 import { isLeft } from 'fp-ts/lib/Either';
 import * as JSONStream from 'JSONStream';
 import * as _ from 'lodash';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 import StrictEventEmitter from 'strict-event-emitter-types';
 
 import * as config from '../config';
diff --git a/src/compose/service.ts b/src/compose/service.ts
index e4a8d68a..4be89701 100644
--- a/src/compose/service.ts
+++ b/src/compose/service.ts
@@ -18,9 +18,9 @@ import {
 } from './types/service';
 import * as ComposeUtils from './utils';
 
-import * as constants from '../lib/constants';
 import * as updateLock from '../lib/update-lock';
 import { sanitiseComposeConfig } from './sanitise';
+import { getPathOnHost } from '../lib/fs-utils';
 
 import log from '../lib/supervisor-console';
 import { EnvVarObject } from '../lib/types';
@@ -900,16 +900,14 @@ export class Service {
 	}
 
 	public handoverCompleteFullPathsOnHost(): string[] {
-		return [
-			path.join(this.handoverCompletePathOnHost(), 'handover-complete'),
-			path.join(this.handoverCompletePathOnHost(), 'resin-kill-me'),
-		];
-	}
-
-	private handoverCompletePathOnHost(): string {
-		return path.join(
-			constants.rootMountPoint,
-			updateLock.lockPath(this.appId || 0, this.serviceName || ''),
+		const lockPath = updateLock.lockPath(
+			this.appId || 0,
+			this.serviceName || '',
+		);
+		return getPathOnHost(
+			...['handover-complete', 'resin-kill-me'].map((tail) =>
+				path.join(lockPath, tail),
+			),
 		);
 	}
 
diff --git a/src/config/backends/backend.ts b/src/config/backends/backend.ts
index 0665127a..d21fc1dc 100644
--- a/src/config/backends/backend.ts
+++ b/src/config/backends/backend.ts
@@ -1,8 +1,7 @@
 import * as _ from 'lodash';
-import { child_process } from 'mz';
 
 import * as constants from '../../lib/constants';
-import { writeFileAtomic } from '../../lib/fs-utils';
+import { writeFileAtomic, exec } from '../../lib/fs-utils';
 
 export interface ConfigOptions {
 	[key: string]: string | string[];
@@ -15,7 +14,7 @@ export async function remountAndWriteAtomic(
 	data: string | Buffer,
 ): Promise<void> {
 	// Here's the dangerous part:
-	await child_process.exec(
+	await exec(
 		`mount -t vfat -o remount,rw ${constants.bootBlockDevice} ${bootMountPoint}`,
 	);
 	await writeFileAtomic(file, data);
diff --git a/src/config/backends/config-fs.ts b/src/config/backends/config-fs.ts
index 44caa04f..55872d6f 100644
--- a/src/config/backends/config-fs.ts
+++ b/src/config/backends/config-fs.ts
@@ -1,5 +1,5 @@
 import * as _ from 'lodash';
-import { child_process, fs } from 'mz';
+import { promises as fs } from 'fs';
 import * as path from 'path';
 
 import {
@@ -8,6 +8,7 @@ import {
 	bootMountPoint,
 	remountAndWriteAtomic,
 } from './backend';
+import { exec, exists } from '../../lib/fs-utils';
 import * as constants from '../../lib/constants';
 import * as logger from '../../logger';
 import log from '../../lib/supervisor-console';
@@ -56,7 +57,7 @@ export class ConfigFs extends ConfigBackend {
 
 		const amlSrcPath = path.join(this.SystemAmlFiles, `${aml}.aml`);
 		// log to system log if the AML doesn't exist...
-		if (!(await fs.exists(amlSrcPath))) {
+		if (!(await exists(amlSrcPath))) {
 			log.error(`Missing AML for \'${aml}\'. Unable to load.`);
 			if (logger) {
 				logger.logSystemMessage(
@@ -80,9 +81,7 @@ export class ConfigFs extends ConfigBackend {
 			log.info(`Loading AML ${aml}`);
 			// we use `cat` here as this didn't work when using `cp` and all
 			// examples of this loading mechanism use `cat`.
-			await child_process.exec(
-				`cat ${amlSrcPath} > ${path.join(amlDstPath, 'aml')}`,
-			);
+			await exec(`cat ${amlSrcPath} > ${path.join(amlDstPath, 'aml')}`);
 
 			const [oemId, oemTableId, oemRevision] = await Promise.all([
 				fs.readFile(path.join(amlDstPath, 'oem_id'), 'utf8'),
@@ -101,7 +100,7 @@ export class ConfigFs extends ConfigBackend {
 
 	private async readConfigJSON(): Promise<ConfigfsConfig> {
 		// if we don't yet have a config file, just return an empty result...
-		if (!(await fs.exists(this.ConfigFilePath))) {
+		if (!(await exists(this.ConfigFilePath))) {
 			log.info('Empty ConfigFS config file');
 			return {};
 		}
@@ -134,7 +133,7 @@ export class ConfigFs extends ConfigBackend {
 			await super.initialise();
 
 			// load the acpi_configfs module...
-			await child_process.exec('modprobe acpi_configfs');
+			await exec('modprobe acpi_configfs');
 
 			// read the existing config file...
 			const config = await this.readConfigJSON();
diff --git a/src/config/backends/config-txt.ts b/src/config/backends/config-txt.ts
index bb387887..481a4242 100644
--- a/src/config/backends/config-txt.ts
+++ b/src/config/backends/config-txt.ts
@@ -1,5 +1,5 @@
 import * as _ from 'lodash';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 
 import {
 	ConfigOptions,
@@ -9,6 +9,7 @@ import {
 } from './backend';
 import * as constants from '../../lib/constants';
 import log from '../../lib/supervisor-console';
+import { exists } from '../../lib/fs-utils';
 
 /**
  * A backend to handle Raspberry Pi host configuration
@@ -61,7 +62,7 @@ export class ConfigTxt extends ConfigBackend {
 	public async getBootConfig(): Promise<ConfigOptions> {
 		let configContents = '';
 
-		if (await fs.exists(ConfigTxt.bootConfigPath)) {
+		if (await exists(ConfigTxt.bootConfigPath)) {
 			configContents = await fs.readFile(ConfigTxt.bootConfigPath, 'utf-8');
 		} else {
 			await fs.writeFile(ConfigTxt.bootConfigPath, '');
diff --git a/src/config/backends/extlinux.ts b/src/config/backends/extlinux.ts
index a19bc6cc..4c5b3ad7 100644
--- a/src/config/backends/extlinux.ts
+++ b/src/config/backends/extlinux.ts
@@ -1,5 +1,5 @@
 import * as _ from 'lodash';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 import * as semver from 'semver';
 
 import {
diff --git a/src/config/backends/extra-uEnv.ts b/src/config/backends/extra-uEnv.ts
index 01577a6f..90f88fc3 100644
--- a/src/config/backends/extra-uEnv.ts
+++ b/src/config/backends/extra-uEnv.ts
@@ -1,5 +1,5 @@
 import * as _ from 'lodash';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 
 import {
 	ConfigOptions,
@@ -10,6 +10,7 @@ import {
 import * as constants from '../../lib/constants';
 import log from '../../lib/supervisor-console';
 import { ExtraUEnvError } from '../../lib/errors';
+import { exists } from '../../lib/fs-utils';
 
 /**
  * Entry describes the configurable items in an extra_uEnv file
@@ -63,7 +64,7 @@ export class ExtraUEnv extends ConfigBackend {
 			(deviceType.endsWith('-nano') ||
 				deviceType.endsWith('-nano-emmc') ||
 				deviceType.endsWith('-tx2')) &&
-			(await fs.exists(ExtraUEnv.bootConfigPath))
+			(await exists(ExtraUEnv.bootConfigPath))
 		);
 	}
 
diff --git a/src/config/backends/splash-image.ts b/src/config/backends/splash-image.ts
index 6fa9a587..784e2436 100644
--- a/src/config/backends/splash-image.ts
+++ b/src/config/backends/splash-image.ts
@@ -1,9 +1,10 @@
 import * as Bluebird from 'bluebird';
 import * as _ from 'lodash';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 import * as path from 'path';
 
 import * as constants from '../../lib/constants';
+import { exists } from '../../lib/fs-utils';
 import log from '../../lib/supervisor-console';
 import {
 	bootMountPoint,
@@ -126,7 +127,7 @@ export class SplashImage extends ConfigBackend {
 
 			// The default boot image file has already
 			// been created
-			if (await fs.exists(SplashImage.DEFAULT)) {
+			if (await exists(SplashImage.DEFAULT)) {
 				return this;
 			}
 
diff --git a/src/config/configJson.ts b/src/config/configJson.ts
index 0b2a45a3..6829805d 100644
--- a/src/config/configJson.ts
+++ b/src/config/configJson.ts
@@ -1,6 +1,6 @@
 import * as Bluebird from 'bluebird';
 import * as _ from 'lodash';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 import * as path from 'path';
 
 import * as constants from '../lib/constants';
@@ -86,11 +86,6 @@ export default class ConfigJsonConfigBackend {
 		});
 	}
 
-	public async path(): Promise<string> {
-		await this.init();
-		return await this.pathOnHost();
-	}
-
 	private write(): Promise<void> {
 		let atomicWritePossible = true;
 		return this.pathOnHost()
diff --git a/src/config/functions.ts b/src/config/functions.ts
index 6bf85c5a..520372a9 100644
--- a/src/config/functions.ts
+++ b/src/config/functions.ts
@@ -1,7 +1,7 @@
 import * as Bluebird from 'bluebird';
 import * as _ from 'lodash';
 import * as memoizee from 'memoizee';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 import { URL } from 'url';
 
 import supervisorVersion = require('../lib/supervisor-version');
diff --git a/src/device-state.ts b/src/device-state.ts
index 9ab41f5e..67e72448 100644
--- a/src/device-state.ts
+++ b/src/device-state.ts
@@ -1,5 +1,4 @@
 import * as Bluebird from 'bluebird';
-import * as bodyParser from 'body-parser';
 import { stripIndent } from 'common-tags';
 import { EventEmitter } from 'events';
 import * as express from 'express';
@@ -95,8 +94,8 @@ function validateState(state: any): asserts state is TargetState {
 // device api stuff in ./device-api
 function createDeviceStateRouter() {
 	router = express.Router();
-	router.use(bodyParser.urlencoded({ limit: '10mb', extended: true }));
-	router.use(bodyParser.json({ limit: '10mb' }));
+	router.use(express.urlencoded({ limit: '10mb', extended: true }));
+	router.use(express.json({ limit: '10mb' }));
 
 	const rebootOrShutdown = async (
 		req: express.Request,
@@ -463,15 +462,11 @@ export async function loadInitialState() {
 // breaks loose due to the liberal any casting
 function emitAsync<T extends keyof DeviceStateEvents>(
 	ev: T,
-	...args: DeviceStateEvents[T] extends (...args: any) => void
-		? Parameters<DeviceStateEvents[T]>
+	...args: DeviceStateEvents[T] extends (...args: infer TArgs) => void
+		? TArgs
 		: Array<DeviceStateEvents[T]>
 ) {
-	if (_.isArray(args)) {
-		return setImmediate(() => events.emit(ev as any, ...(args as any)));
-	} else {
-		return setImmediate(() => events.emit(ev as any, args));
-	}
+	return setImmediate(() => events.emit(ev as any, ...args));
 }
 
 const readLockTarget = () =>
diff --git a/src/device-state/preload.ts b/src/device-state/preload.ts
index 9e58cdd9..e9922c12 100644
--- a/src/device-state/preload.ts
+++ b/src/device-state/preload.ts
@@ -1,5 +1,5 @@
 import * as _ from 'lodash';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 
 import { Image, imageFromService } from '../compose/images';
 import * as deviceState from '../device-state';
diff --git a/src/host-config.ts b/src/host-config.ts
index c7c4fb8a..2947e10f 100644
--- a/src/host-config.ts
+++ b/src/host-config.ts
@@ -1,20 +1,14 @@
 import * as Bluebird from 'bluebird';
 import { stripIndent } from 'common-tags';
 import * as _ from 'lodash';
-import * as mkdirCb from 'mkdirp';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 import * as path from 'path';
 
 import * as config from './config';
 import * as constants from './lib/constants';
 import * as dbus from './lib/dbus';
 import { ENOENT } from './lib/errors';
-import { writeFileAtomic } from './lib/fs-utils';
-
-const mkdirp = Bluebird.promisify(mkdirCb) as (
-	path: string,
-	opts?: any,
-) => Bluebird<mkdirCb.Made>;
+import { writeFileAtomic, mkdirp, unlinkAll } from './lib/fs-utils';
 
 const redsocksHeader = stripIndent`
 	base {
@@ -131,13 +125,7 @@ function generateRedsocksConfEntries(conf: ProxyConfig): string {
 
 async function setProxy(maybeConf: ProxyConfig | null): Promise<void> {
 	if (_.isEmpty(maybeConf)) {
-		try {
-			await Promise.all([fs.unlink(redsocksConfPath), fs.unlink(noProxyPath)]);
-		} catch (e) {
-			if (!ENOENT(e)) {
-				throw e;
-			}
-		}
+		await unlinkAll(redsocksConfPath, noProxyPath);
 	} else {
 		// We know that maybeConf is not null due to the _.isEmpty check above,
 		// but the compiler doesn't
diff --git a/src/lib/fs-utils.ts b/src/lib/fs-utils.ts
index 7194b706..99c10cea 100644
--- a/src/lib/fs-utils.ts
+++ b/src/lib/fs-utils.ts
@@ -1,42 +1,84 @@
-import * as Bluebird from 'bluebird';
 import * as _ from 'lodash';
-import { fs } from 'mz';
-import * as Path from 'path';
-import * as constants from './constants';
-import { ENOENT } from './errors';
+import { promises as fs } from 'fs';
+import * as path from 'path';
+import { exec as execSync } from 'child_process';
+import { promisify } from 'util';
 
-export function writeAndSyncFile(
-	path: string,
+import * as constants from './constants';
+
+export const exec = promisify(execSync);
+
+export async function writeAndSyncFile(
+	pathName: string,
 	data: string | Buffer,
-): Bluebird<void> {
-	return Bluebird.resolve(fs.open(path, 'w')).then((fd) => {
-		_.isString(data)
-			? fs.write(fd, data, 0, 'utf8')
-			: fs
-					.write(fd, data, 0, data.length)
-					.then(() => fs.fsync(fd))
-					.then(() => fs.close(fd));
-	});
+): Promise<void> {
+	const file = await fs.open(pathName, 'w');
+	if (typeof data === 'string') {
+		await file.write(data, 0, 'utf8');
+	} else {
+		await file.write(data, 0, data.length);
+	}
+	await file.sync();
+	await file.close();
 }
 
-export function writeFileAtomic(
-	path: string,
+export async function writeFileAtomic(
+	pathName: string,
 	data: string | Buffer,
-): Bluebird<void> {
-	return Bluebird.resolve(writeAndSyncFile(`${path}.new`, data)).then(() =>
-		fs.rename(`${path}.new`, path),
+): Promise<void> {
+	await writeAndSyncFile(`${pathName}.new`, data);
+	await fs.rename(`${pathName}.new`, pathName);
+}
+
+export async function safeRename(src: string, dest: string): Promise<void> {
+	await fs.rename(src, dest);
+	const file = await fs.open(path.dirname(dest), 'r');
+	await file.sync();
+	await file.close();
+}
+
+export async function exists(p: string): Promise<boolean> {
+	try {
+		await fs.access(p);
+		return true;
+	} catch {
+		return false;
+	}
+}
+
+/**
+ * Check if a path exists as a direct child of the device's root mountpoint,
+ * which is equal to constants.rootMountPoint (`/mnt/root`).
+ */
+export function pathExistsOnHost(pathName: string): Promise<boolean> {
+	return exists(path.join(constants.rootMountPoint, pathName));
+}
+
+/**
+ * Recursively create directories until input directory.
+ * Equivalent to mkdirp package, which uses this under the hood.
+ */
+export async function mkdirp(pathName: string): Promise<void> {
+	await fs.mkdir(pathName, { recursive: true });
+}
+
+/**
+ * Safe unlink with built-in catch for invalid paths, to remove need
+ * for catch implementation everywhere else unlink is needed.
+ */
+export async function unlinkAll(...paths: string[]): Promise<void> {
+	await Promise.all(
+		paths.map((pathName) =>
+			fs.unlink(pathName).catch(() => {
+				/* Ignore nonexistent paths */
+			}),
+		),
 	);
 }
 
-export function safeRename(src: string, dest: string): Bluebird<void> {
-	return Bluebird.resolve(fs.rename(src, dest))
-		.then(() => fs.open(Path.dirname(dest), 'r'))
-		.tap(fs.fsync)
-		.then(fs.close);
-}
-
-export function pathExistsOnHost(p: string): Bluebird<boolean> {
-	return Bluebird.resolve(fs.stat(Path.join(constants.rootMountPoint, p)))
-		.return(true)
-		.catchReturn(ENOENT, false);
+/**
+ * Get one or more paths as they exist in relation to host OS's root.
+ */
+export function getPathOnHost(...paths: string[]): string[] {
+	return paths.map((p: string) => path.join(constants.rootMountPoint, p));
 }
diff --git a/src/lib/iptables.ts b/src/lib/iptables.ts
index 7fcf9304..38d1a24c 100644
--- a/src/lib/iptables.ts
+++ b/src/lib/iptables.ts
@@ -1,5 +1,5 @@
 import * as _ from 'lodash';
-import { child_process } from 'mz';
+import { spawn } from 'child_process';
 import { Readable } from 'stream';
 import { TypedError } from 'typed-error';
 
@@ -168,7 +168,7 @@ const iptablesRestoreAdaptor: RuleAdaptor = async (
 			stdinStream.push(null);
 
 			// run the restore...
-			const proc = child_process.spawn(cmd, args, { shell: true });
+			const proc = spawn(cmd, args, { shell: true });
 
 			// pipe the rules...
 			stdinStream.pipe(proc.stdin);
diff --git a/src/lib/mac-address.ts b/src/lib/mac-address.ts
index 02414cf9..c53b1b5b 100644
--- a/src/lib/mac-address.ts
+++ b/src/lib/mac-address.ts
@@ -1,11 +1,12 @@
 import * as _ from 'lodash';
-import { promises as fs, exists } from 'mz/fs';
+import { promises as fs } from 'fs';
 import * as path from 'path';
+import { TypedError } from 'typed-error';
 
 import log from './supervisor-console';
 import { shouldReportInterface } from '../network';
+import { exists } from './fs-utils';
 
-import { TypedError } from 'typed-error';
 export class MacAddressError extends TypedError {}
 
 export async function getAll(sysClassNet: string): Promise<string | undefined> {
diff --git a/src/lib/migration.ts b/src/lib/migration.ts
index 49b57583..fd3abf4e 100644
--- a/src/lib/migration.ts
+++ b/src/lib/migration.ts
@@ -1,11 +1,9 @@
 import * as Bluebird from 'bluebird';
 import * as _ from 'lodash';
-import * as mkdirp from 'mkdirp';
-import { child_process, fs } from 'mz';
+import { promises as fs } from 'fs';
 import * as path from 'path';
 import * as rimraf from 'rimraf';
 
-const mkdirpAsync = Bluebird.promisify(mkdirp);
 const rimrafAsync = Bluebird.promisify(rimraf);
 
 import * as apiBinder from '../api-binder';
@@ -23,7 +21,7 @@ import {
 	InternalInconsistencyError,
 } from '../lib/errors';
 import { docker } from '../lib/docker-utils';
-import { pathExistsOnHost } from '../lib/fs-utils';
+import { exec, pathExistsOnHost, mkdirp } from '../lib/fs-utils';
 import { log } from '../lib/supervisor-console';
 import type {
 	AppsJsonFormat,
@@ -298,8 +296,8 @@ export async function loadBackupFromMigration(
 		const backupPath = path.join(constants.rootMountPoint, 'mnt/data/backup');
 		// We clear this path in case it exists from an incomplete run of this function
 		await rimrafAsync(backupPath);
-		await mkdirpAsync(backupPath);
-		await child_process.exec(`tar -xzf backup.tgz -C ${backupPath}`, {
+		await mkdirp(backupPath);
+		await exec(`tar -xzf backup.tgz -C ${backupPath}`, {
 			cwd: path.join(constants.rootMountPoint, 'mnt/data'),
 		});
 
diff --git a/src/lib/os-release.ts b/src/lib/os-release.ts
index b66a51f8..7a11d37b 100644
--- a/src/lib/os-release.ts
+++ b/src/lib/os-release.ts
@@ -1,7 +1,8 @@
 import * as _ from 'lodash';
-import { child_process, fs } from 'mz';
+import { promises as fs } from 'fs';
 
 import { InternalInconsistencyError } from './errors';
+import { exec } from './fs-utils';
 import log from './supervisor-console';
 
 // Retrieve the data for the OS once only per path
@@ -69,7 +70,7 @@ const L4T_REGEX = /^.*-l4t-r(\d+\.\d+(\.?\d+)?).*$/;
 export async function getL4tVersion(): Promise<string | undefined> {
 	// We call `uname -r` on the host, and look for l4t
 	try {
-		const [stdout] = await child_process.exec('uname -r');
+		const { stdout } = await exec('uname -r');
 		const match = L4T_REGEX.exec(stdout.toString().trim());
 		if (match == null) {
 			return;
diff --git a/src/lib/system-info.ts b/src/lib/system-info.ts
index 7a56282f..eae5f9bb 100644
--- a/src/lib/system-info.ts
+++ b/src/lib/system-info.ts
@@ -1,6 +1,8 @@
 import * as systeminformation from 'systeminformation';
 import * as _ from 'lodash';
-import { fs, child_process } from 'mz';
+import { promises as fs } from 'fs';
+
+import { exec } from './fs-utils';
 
 export async function getCpuUsage(): Promise<number> {
 	const cpuData = await systeminformation.currentLoad();
@@ -78,7 +80,7 @@ export async function getCpuId(): Promise<string | undefined> {
 const undervoltageRegex = /under.*voltage/;
 export async function undervoltageDetected(): Promise<boolean> {
 	try {
-		const [dmesgStdout] = await child_process.exec('dmesg');
+		const { stdout: dmesgStdout } = await exec('dmesg');
 		return undervoltageRegex.test(dmesgStdout.toString());
 	} catch {
 		return false;
diff --git a/src/lib/update-lock.ts b/src/lib/update-lock.ts
index 37176542..be505053 100644
--- a/src/lib/update-lock.ts
+++ b/src/lib/update-lock.ts
@@ -1,12 +1,12 @@
 import * as Bluebird from 'bluebird';
 import * as lockFileLib from 'lockfile';
 import * as _ from 'lodash';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 import * as path from 'path';
 import * as Lock from 'rwlock';
 
-import constants = require('./constants');
 import { ENOENT, UpdatesLockedError } from './errors';
+import { getPathOnHost } from './fs-utils';
 
 type asyncLockFile = typeof lockFileLib & {
 	unlockAsync(path: string): Bluebird<void>;
@@ -19,17 +19,19 @@ export type LockCallback = (
 	fn: () => PromiseLike<void>,
 ) => Bluebird<void>;
 
-function baseLockPath(appId: number): string {
-	return path.join('/tmp/balena-supervisor/services', appId.toString());
-}
-
-export function lockPath(appId: number, serviceName: string): string {
-	return path.join(baseLockPath(appId), serviceName);
+export function lockPath(appId: number, serviceName?: string): string {
+	return path.join(
+		'/tmp/balena-supervisor/services',
+		appId.toString(),
+		serviceName ?? '',
+	);
 }
 
 function lockFilesOnHost(appId: number, serviceName: string): string[] {
-	return ['updates.lock', 'resin-updates.lock'].map((filename) =>
-		path.join(constants.rootMountPoint, lockPath(appId, serviceName), filename),
+	return getPathOnHost(
+		...['updates.lock', 'resin-updates.lock'].map((filename) =>
+			path.join(lockPath(appId), serviceName, filename),
+		),
 	);
 }
 
@@ -79,10 +81,7 @@ export function lock(
 		}
 		return writeLock(appId)
 			.tap((release: () => void) => {
-				const lockDir = path.join(
-					constants.rootMountPoint,
-					baseLockPath(appId),
-				);
+				const [lockDir] = getPathOnHost(lockPath(appId));
 
 				return Bluebird.resolve(fs.readdir(lockDir))
 					.catchReturn(ENOENT, [])
diff --git a/src/network.ts b/src/network.ts
index 63c7e996..3b4cd43d 100644
--- a/src/network.ts
+++ b/src/network.ts
@@ -1,6 +1,6 @@
 import * as Bluebird from 'bluebird';
 import * as _ from 'lodash';
-import { fs } from 'mz';
+import { promises as fs, watch } from 'fs';
 import * as networkCheck from 'network-checker';
 import * as os from 'os';
 import * as url from 'url';
@@ -74,7 +74,7 @@ export const startConnectivityCheck = _.once(
 				log.debug('VPN status path exists.');
 			})
 			.then(() => {
-				fs.watch(constants.vpnStatusPath, vpnStatusInotifyCallback);
+				watch(constants.vpnStatusPath, vpnStatusInotifyCallback);
 			});
 
 		if (enable) {
diff --git a/src/proxyvisor.js b/src/proxyvisor.js
index 08ae0fe1..80845352 100644
--- a/src/proxyvisor.js
+++ b/src/proxyvisor.js
@@ -1,7 +1,10 @@
 import * as Promise from 'bluebird';
 import * as _ from 'lodash';
 import * as express from 'express';
-import { fs, child_process as childProcess } from 'mz';
+import { promises as fs } from 'fs';
+import * as path from 'path';
+import * as url from 'url';
+
 import * as request from './lib/request';
 import * as constants from './lib/constants';
 import {
@@ -9,26 +12,20 @@ import {
 	validStringOrUndefined,
 	validObjectOrUndefined,
 } from './lib/validation';
-import * as path from 'path';
-import * as mkdirp from 'mkdirp';
-import * as bodyParser from 'body-parser';
-import * as url from 'url';
+import { log } from './lib/supervisor-console';
+import * as dockerUtils from './lib/docker-utils';
+import { InternalInconsistencyError } from './lib/errors';
+import * as apiHelper from './lib/api-helper';
+import { exec, mkdirp } from './lib/fs-utils';
 
 import { normalise } from './compose/images';
-import { log } from './lib/supervisor-console';
 import * as db from './db';
 import * as config from './config';
-import * as dockerUtils from './lib/docker-utils';
 import * as logger from './logger';
-import { InternalInconsistencyError } from './lib/errors';
-
 import * as apiBinder from './api-binder';
-import * as apiHelper from './lib/api-helper';
 import * as dbFormat from './device-state/db-format';
 import * as deviceConfig from './device-config';
 
-const mkdirpAsync = Promise.promisify(mkdirp);
-
 const isDefined = _.negate(_.isUndefined);
 
 const parseDeviceFields = function (device) {
@@ -52,8 +49,8 @@ const getTarArchive = (source, destination) =>
 	fs
 		.lstat(destination)
 		.catch(() =>
-			mkdirpAsync(path.dirname(destination)).then(() =>
-				childProcess.exec(`tar -cvf '${destination}' *`, { cwd: source }),
+			mkdirp(path.dirname(destination)).then(() =>
+				exec(`tar -cvf '${destination}' *`, { cwd: source }),
 			),
 		);
 
@@ -92,8 +89,8 @@ const formatCurrentAsState = (device) => ({
 
 const createProxyvisorRouter = function (proxyvisor) {
 	const router = express.Router();
-	router.use(bodyParser.urlencoded({ limit: '10mb', extended: true }));
-	router.use(bodyParser.json({ limit: '10mb' }));
+	router.use(express.urlencoded({ limit: '10mb', extended: true }));
+	router.use(express.json({ limit: '10mb' }));
 	router.get('/v1/devices', async (_req, res) => {
 		try {
 			const fields = await db.models('dependentDevice').select();
diff --git a/sync/device.ts b/sync/device.ts
index b78de696..84586db4 100644
--- a/sync/device.ts
+++ b/sync/device.ts
@@ -4,11 +4,12 @@ import * as _ from 'lodash';
 import { Builder } from 'resin-docker-build';
 
 import { promises as fs } from 'fs';
-import { child_process } from 'mz';
 import * as Path from 'path';
 import { Duplex, Readable } from 'stream';
 import * as tar from 'tar-stream';
 
+import { exec } from '../src/lib/fs-utils';
+
 export function getDocker(deviceAddress: string): Docker {
 	return new Docker({
 		host: deviceAddress,
@@ -146,7 +147,7 @@ async function tarDirectory(
 // Absolutely no escaping in this function, just be careful
 async function runSshCommand(address: string, command: string) {
 	// TODO: Make the port configurable
-	const [stdout] = await child_process.exec(
+	const { stdout } = await exec(
 		'ssh -p 22222 -o LogLevel=ERROR ' +
 			'-o StrictHostKeyChecking=no ' +
 			'-o UserKnownHostsFile=/dev/null ' +
diff --git a/sync/sync.ts b/sync/sync.ts
index b56d0689..a69aaebc 100644
--- a/sync/sync.ts
+++ b/sync/sync.ts
@@ -1,10 +1,8 @@
-import * as packageJson from '../package.json';
-
 import * as livepush from 'livepush';
-
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 import * as yargs from 'yargs';
 
+import * as packageJson from '../package.json';
 import * as device from './device';
 import * as init from './init';
 import { startLivepush } from './livepush';
diff --git a/test/01-constants.spec.ts b/test/01-constants.spec.ts
index d0111f8d..2f81d78d 100644
--- a/test/01-constants.spec.ts
+++ b/test/01-constants.spec.ts
@@ -1,7 +1,4 @@
-import ChaiConfig = require('./lib/chai-config');
-
-const { expect } = ChaiConfig;
-
+import { expect } from 'chai';
 import constants = require('../src/lib/constants');
 
 describe('constants', function () {
diff --git a/test/02-db.spec.ts b/test/02-db.spec.ts
index 0a8b33c2..794b7132 100644
--- a/test/02-db.spec.ts
+++ b/test/02-db.spec.ts
@@ -1,13 +1,10 @@
 import * as Bluebird from 'bluebird';
 import * as Knex from 'knex';
-import { fs } from 'mz';
 
-import ChaiConfig = require('./lib/chai-config');
+import { expect } from 'chai';
 import prepare = require('./lib/prepare');
-
 import * as constants from '../src/lib/constants';
-
-const { expect } = ChaiConfig;
+import { exists } from '../src/lib/fs-utils';
 
 async function createOldDatabase(path: string) {
 	const knex = Knex({
@@ -63,7 +60,7 @@ describe('Database Migrations', () => {
 
 		const testDb = await import('../src/db');
 		await testDb.initialized;
-		await fs.stat(databasePath);
+		expect(await exists(databasePath)).to.be.true;
 	});
 
 	it('adds new fields and removes old ones in an old database', async () => {
@@ -109,9 +106,8 @@ describe('Database', () => {
 	it('initializes correctly, running the migrations', () => {
 		return expect(db.initialized).to.be.fulfilled;
 	});
-	it('creates a database at the path from an env var', () => {
-		const promise = fs.stat(process.env.DATABASE_PATH!);
-		return expect(promise).to.be.fulfilled;
+	it('creates a database at the path from an env var', async () => {
+		expect(await exists(process.env.DATABASE_PATH!)).to.be.true;
 	});
 	it('creates a deviceConfig table with a single default value', async () => {
 		const deviceConfig = await db.models('deviceConfig').select();
diff --git a/test/03-config.spec.ts b/test/03-config.spec.ts
index 7a985239..d0393990 100644
--- a/test/03-config.spec.ts
+++ b/test/03-config.spec.ts
@@ -1,8 +1,8 @@
 import * as _ from 'lodash';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 import { SinonStub, stub } from 'sinon';
 
-import chai = require('./lib/chai-config');
+import * as chai from 'chai';
 import prepare = require('./lib/prepare');
 import * as conf from '../src/config';
 
@@ -20,12 +20,6 @@ describe('Config', () => {
 		await conf.initialized;
 	});
 
-	it('uses the correct config.json path', async () => {
-		expect(await conf.configJsonBackend.path()).to.equal(
-			'test/data/config.json',
-		);
-	});
-
 	it('reads and exposes values from the config.json', async () => {
 		const id = await conf.get('applicationId');
 		return expect(id).to.equal(78373);
diff --git a/test/05-device-state.spec.ts b/test/05-device-state.spec.ts
index 41a3d8fd..0b482f3f 100644
--- a/test/05-device-state.spec.ts
+++ b/test/05-device-state.spec.ts
@@ -1,7 +1,7 @@
 import * as _ from 'lodash';
 import { stub } from 'sinon';
 
-import chai = require('./lib/chai-config');
+import * as chai from 'chai';
 import { StatusCodeError } from '../src/lib/errors';
 import prepare = require('./lib/prepare');
 import * as dockerUtils from '../src/lib/docker-utils';
diff --git a/test/06-validation.spec.ts b/test/06-validation.spec.ts
index 822e280c..4c072dd6 100644
--- a/test/06-validation.spec.ts
+++ b/test/06-validation.spec.ts
@@ -1,5 +1,5 @@
 import * as _ from 'lodash';
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 
 import * as validation from '../src/lib/validation';
 
diff --git a/test/07-blink.spec.ts b/test/07-blink.spec.ts
index d0590970..9c50c492 100644
--- a/test/07-blink.spec.ts
+++ b/test/07-blink.spec.ts
@@ -1,5 +1,5 @@
-import { fs } from 'mz';
-import { expect } from './lib/chai-config';
+import { promises as fs } from 'fs';
+import { expect } from 'chai';
 
 import blink = require('../src/lib/blink');
 import constants = require('../src/lib/constants');
diff --git a/test/08-event-tracker.spec.ts b/test/08-event-tracker.spec.ts
index b782cbbf..b8ae5fc9 100644
--- a/test/08-event-tracker.spec.ts
+++ b/test/08-event-tracker.spec.ts
@@ -1,7 +1,7 @@
 import * as mixpanel from 'mixpanel';
 import { SinonStub, stub, spy, SinonSpy } from 'sinon';
 
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 
 import log from '../src/lib/supervisor-console';
 import supervisorVersion = require('../src/lib/supervisor-version');
diff --git a/test/09-network.spec.ts b/test/09-network.spec.ts
index 47b86d87..6fa6d6a8 100644
--- a/test/09-network.spec.ts
+++ b/test/09-network.spec.ts
@@ -1,8 +1,8 @@
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 import * as os from 'os';
 import { stub, spy } from 'sinon';
 
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import Log from '../src/lib/supervisor-console';
 import * as network from '../src/network';
 
diff --git a/test/10-api-binder.spec.ts b/test/10-api-binder.spec.ts
index 8af666e2..979afbd9 100644
--- a/test/10-api-binder.spec.ts
+++ b/test/10-api-binder.spec.ts
@@ -1,5 +1,5 @@
 import { stripIndent } from 'common-tags';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 import { Server } from 'net';
 import { SinonSpy, SinonStub, spy, stub } from 'sinon';
 
@@ -7,7 +7,7 @@ import prepare = require('./lib/prepare');
 import * as config from '../src/config';
 import * as deviceState from '../src/device-state';
 import Log from '../src/lib/supervisor-console';
-import chai = require('./lib/chai-config');
+import { expect } from 'chai';
 import balenaAPI = require('./lib/mocked-balena-api');
 import { schema } from '../src/config/schema';
 import ConfigJsonConfigBackend from '../src/config/configJson';
@@ -21,7 +21,6 @@ import { DeviceNotFoundError } from '../src/lib/errors';
 
 import { eventTrackSpy } from './lib/mocked-event-tracker';
 
-const { expect } = chai;
 let ApiBinder: typeof import('../src/api-binder');
 
 class ExpectedError extends TypedError {}
diff --git a/test/11-logger.spec.ts b/test/11-logger.spec.ts
index cd603d8b..9437f8da 100644
--- a/test/11-logger.spec.ts
+++ b/test/11-logger.spec.ts
@@ -2,7 +2,7 @@ import * as https from 'https';
 import * as stream from 'stream';
 import * as zlib from 'zlib';
 import * as Promise from 'bluebird';
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import * as sinon from 'sinon';
 
 import { ContainerLogs } from '../src/logging/container';
diff --git a/test/12-device-config.spec.ts b/test/12-device-config.spec.ts
index 472706e1..dc6ba119 100644
--- a/test/12-device-config.spec.ts
+++ b/test/12-device-config.spec.ts
@@ -1,8 +1,8 @@
 import { stripIndent } from 'common-tags';
-import { child_process, fs } from 'mz';
+import { promises as fs } from 'fs';
 import { SinonStub, stub, spy, SinonSpy } from 'sinon';
 
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import * as deviceConfig from '../src/device-config';
 import * as fsUtils from '../src/lib/fs-utils';
 import * as logger from '../src/logger';
@@ -131,7 +131,7 @@ describe('Device Backend Config', () => {
 
 	it('writes the target config.txt', async () => {
 		stub(fsUtils, 'writeFileAtomic').resolves();
-		stub(child_process, 'exec').resolves();
+		stub(fsUtils, 'exec').resolves();
 		const current = {
 			HOST_CONFIG_initramfs: 'initramf.gz 0x00800000',
 			HOST_CONFIG_dtparam: '"i2c=on","audio=on"',
@@ -154,7 +154,7 @@ describe('Device Backend Config', () => {
 
 		// @ts-ignore accessing private value
 		await deviceConfig.setBootConfig(configTxtBackend, target);
-		expect(child_process.exec).to.be.calledOnce;
+		expect(fsUtils.exec).to.be.calledOnce;
 		expect(logSpy).to.be.calledTwice;
 		expect(logSpy.getCall(1).args[2]).to.equal('Apply boot config success');
 		expect(fsUtils.writeFileAtomic).to.be.calledWith(
@@ -171,12 +171,12 @@ describe('Device Backend Config', () => {
 
 		// Restore stubs
 		(fsUtils.writeFileAtomic as SinonStub).restore();
-		(child_process.exec as SinonStub).restore();
+		(fsUtils.exec as SinonStub).restore();
 	});
 
 	it('ensures required fields are written to config.txt', async () => {
 		stub(fsUtils, 'writeFileAtomic').resolves();
-		stub(child_process, 'exec').resolves();
+		stub(fsUtils, 'exec').resolves();
 		stub(config, 'get').withArgs('deviceType').resolves('fincm3');
 		const current = {
 			HOST_CONFIG_initramfs: 'initramf.gz 0x00800000',
@@ -200,7 +200,7 @@ describe('Device Backend Config', () => {
 
 		// @ts-ignore accessing private value
 		await deviceConfig.setBootConfig(configTxtBackend, target);
-		expect(child_process.exec).to.be.calledOnce;
+		expect(fsUtils.exec).to.be.calledOnce;
 		expect(logSpy).to.be.calledTwice;
 		expect(logSpy.getCall(1).args[2]).to.equal('Apply boot config success');
 		expect(fsUtils.writeFileAtomic).to.be.calledWith(
@@ -218,7 +218,7 @@ describe('Device Backend Config', () => {
 
 		// Restore stubs
 		(fsUtils.writeFileAtomic as SinonStub).restore();
-		(child_process.exec as SinonStub).restore();
+		(fsUtils.exec as SinonStub).restore();
 		(config.get as SinonStub).restore();
 	});
 
@@ -269,7 +269,7 @@ describe('Device Backend Config', () => {
 	describe('Extlinux files', () => {
 		it('should correctly write to extlinux.conf files', async () => {
 			stub(fsUtils, 'writeFileAtomic').resolves();
-			stub(child_process, 'exec').resolves();
+			stub(fsUtils, 'exec').resolves();
 
 			const current = {};
 			const target = {
@@ -284,7 +284,7 @@ describe('Device Backend Config', () => {
 
 			// @ts-ignore accessing private value
 			await deviceConfig.setBootConfig(extlinuxBackend, target);
-			expect(child_process.exec).to.be.calledOnce;
+			expect(fsUtils.exec).to.be.calledOnce;
 			expect(logSpy).to.be.calledTwice;
 			expect(logSpy.getCall(1).args[2]).to.equal('Apply boot config success');
 			expect(fsUtils.writeFileAtomic).to.be.calledWith(
@@ -303,7 +303,7 @@ describe('Device Backend Config', () => {
 
 			// Restore stubs
 			(fsUtils.writeFileAtomic as SinonStub).restore();
-			(child_process.exec as SinonStub).restore();
+			(fsUtils.exec as SinonStub).restore();
 		});
 	});
 
@@ -395,7 +395,7 @@ describe('Device Backend Config', () => {
 	describe('ConfigFS files', () => {
 		it('should correctly write to configfs.json files', async () => {
 			stub(fsUtils, 'writeFileAtomic').resolves();
-			stub(child_process, 'exec').resolves();
+			stub(fsUtils, 'exec').resolves();
 
 			const current = {};
 			const target = {
@@ -414,7 +414,7 @@ describe('Device Backend Config', () => {
 
 			// @ts-ignore accessing private value
 			await deviceConfig.setBootConfig(configFsBackend, target);
-			expect(child_process.exec).to.be.calledOnce;
+			expect(fsUtils.exec).to.be.calledOnce;
 			expect(logSpy).to.be.calledTwice;
 			expect(logSpy.getCall(1).args[2]).to.equal('Apply boot config success');
 			expect(fsUtils.writeFileAtomic).to.be.calledWith(
@@ -424,13 +424,13 @@ describe('Device Backend Config', () => {
 
 			// Restore stubs
 			(fsUtils.writeFileAtomic as SinonStub).restore();
-			(child_process.exec as SinonStub).restore();
+			(fsUtils.exec as SinonStub).restore();
 		});
 
 		it('should correctly load the configfs.json file', async () => {
-			stub(child_process, 'exec').resolves();
+			stub(fsUtils, 'exec').resolves();
 			stub(fsUtils, 'writeFileAtomic').resolves();
-			stub(fs, 'exists').resolves(true);
+			stub(fsUtils, 'exists').resolves(true);
 			stub(fs, 'mkdir').resolves();
 			stub(fs, 'readdir').resolves([]);
 			stub(fs, 'readFile').callsFake((file) => {
@@ -445,20 +445,20 @@ describe('Device Backend Config', () => {
 			});
 
 			await configFsBackend.initialise();
-			expect(child_process.exec).to.be.calledWith('modprobe acpi_configfs');
-			expect(child_process.exec).to.be.calledWith(
+			expect(fsUtils.exec).to.be.calledWith('modprobe acpi_configfs');
+			expect(fsUtils.exec).to.be.calledWith(
 				`mount -t vfat -o remount,rw ${constants.bootBlockDevice} ./test/data/mnt/boot`,
 			);
-			expect(child_process.exec).to.be.calledWith(
+			expect(fsUtils.exec).to.be.calledWith(
 				'cat test/data/boot/acpi-tables/spidev1.1.aml > test/data/sys/kernel/config/acpi/table/spidev1.1/aml',
 			);
-			expect((fs.exists as SinonSpy).callCount).to.equal(2);
+			expect((fsUtils.exists as SinonSpy).callCount).to.equal(2);
 			expect((fs.readFile as SinonSpy).callCount).to.equal(4);
 
 			// Restore stubs
 			(fsUtils.writeFileAtomic as SinonStub).restore();
-			(child_process.exec as SinonStub).restore();
-			(fs.exists as SinonStub).restore();
+			(fsUtils.exec as SinonStub).restore();
+			(fsUtils.exists as SinonStub).restore();
 			(fs.mkdir as SinonStub).restore();
 			(fs.readdir as SinonStub).restore();
 			(fs.readFile as SinonStub).restore();
@@ -537,18 +537,18 @@ describe('Device Backend Config', () => {
 		beforeEach(() => {
 			// Setup stubs
 			stub(fsUtils, 'writeFileAtomic').resolves();
-			stub(child_process, 'exec').resolves();
+			stub(fsUtils, 'exec').resolves();
 		});
 
 		afterEach(() => {
 			// Restore stubs
 			(fsUtils.writeFileAtomic as SinonStub).restore();
-			(child_process.exec as SinonStub).restore();
+			(fsUtils.exec as SinonStub).restore();
 		});
 
 		it('should correctly write to resin-logo.png', async () => {
 			// Devices with balenaOS < 2.51 use resin-logo.png
-			stub(fs, 'readdir').resolves(['resin-logo.png']);
+			stub(fs, 'readdir').resolves(['resin-logo.png'] as any);
 
 			const current = {};
 			const target = {
@@ -568,7 +568,7 @@ describe('Device Backend Config', () => {
 
 			await deviceConfig.setBootConfig(splashImageBackend, target);
 
-			expect(child_process.exec).to.be.calledOnce;
+			expect(fsUtils.exec).to.be.calledOnce;
 			expect(logSpy).to.be.calledTwice;
 			expect(logSpy.getCall(1).args[2]).to.equal('Apply boot config success');
 			expect(fsUtils.writeFileAtomic).to.be.calledOnceWith(
@@ -581,7 +581,7 @@ describe('Device Backend Config', () => {
 
 		it('should correctly write to balena-logo.png', async () => {
 			// Devices with balenaOS >= 2.51 use balena-logo.png
-			stub(fs, 'readdir').resolves(['balena-logo.png']);
+			stub(fs, 'readdir').resolves(['balena-logo.png'] as any);
 
 			const current = {};
 			const target = {
@@ -601,7 +601,7 @@ describe('Device Backend Config', () => {
 
 			await deviceConfig.setBootConfig(splashImageBackend, target);
 
-			expect(child_process.exec).to.be.calledOnce;
+			expect(fsUtils.exec).to.be.calledOnce;
 			expect(logSpy).to.be.calledTwice;
 			expect(logSpy.getCall(1).args[2]).to.equal('Apply boot config success');
 			expect(fsUtils.writeFileAtomic).to.be.calledOnceWith(
@@ -634,7 +634,7 @@ describe('Device Backend Config', () => {
 
 			await deviceConfig.setBootConfig(splashImageBackend, target);
 
-			expect(child_process.exec).to.be.calledOnce;
+			expect(fsUtils.exec).to.be.calledOnce;
 			expect(logSpy).to.be.calledTwice;
 			expect(logSpy.getCall(1).args[2]).to.equal('Apply boot config success');
 			expect(fsUtils.writeFileAtomic).to.be.calledOnceWith(
@@ -646,7 +646,7 @@ describe('Device Backend Config', () => {
 		});
 
 		it('should correctly read the splash logo if different from the default', async () => {
-			stub(fs, 'readdir').resolves(['balena-logo.png']);
+			stub(fs, 'readdir').resolves(['balena-logo.png'] as any);
 
 			const readFileStub: SinonStub = stub(fs, 'readFile').resolves(
 				Buffer.from(png, 'base64') as any,
diff --git a/test/13-application-manager.spec.ts b/test/13-application-manager.spec.ts
index 96533687..25002e93 100644
--- a/test/13-application-manager.spec.ts
+++ b/test/13-application-manager.spec.ts
@@ -10,7 +10,7 @@ import * as deviceState from '../src/device-state';
 import * as dockerUtils from '../src/lib/docker-utils';
 import * as images from '../src/compose/images';
 
-import chai = require('./lib/chai-config');
+import * as chai from 'chai';
 import prepare = require('./lib/prepare');
 import * as db from '../src/db';
 import * as dbFormat from '../src/device-state/db-format';
diff --git a/test/14-conversions.spec.ts b/test/14-conversions.spec.ts
index 97f70457..dfd77496 100644
--- a/test/14-conversions.spec.ts
+++ b/test/14-conversions.spec.ts
@@ -1,4 +1,4 @@
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import * as conversion from '../src/lib/conversions';
 
 describe('conversions', function () {
diff --git a/test/15-ports.spec.ts b/test/15-ports.spec.ts
index 696666a7..23879a18 100644
--- a/test/15-ports.spec.ts
+++ b/test/15-ports.spec.ts
@@ -1,5 +1,5 @@
 import { PortMap, PortRange } from '../src/compose/ports';
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 
 // Force cast `PortMap` as a public version so we can test it
 const PortMapPublic = (PortMap as any) as new (
diff --git a/test/16-config-utils.spec.ts b/test/16-config-utils.spec.ts
index bc7e56a8..2cd711be 100644
--- a/test/16-config-utils.spec.ts
+++ b/test/16-config-utils.spec.ts
@@ -1,7 +1,7 @@
 import { stub } from 'sinon';
 import * as _ from 'lodash';
 
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import * as config from '../src/config';
 import * as configUtils from '../src/config/utils';
 import { ExtraUEnv } from '../src/config/backends/extra-uEnv';
diff --git a/test/18-startup.spec.ts b/test/18-startup.spec.ts
index 389da4ef..6c0309c1 100644
--- a/test/18-startup.spec.ts
+++ b/test/18-startup.spec.ts
@@ -1,5 +1,5 @@
 import { SinonStub, stub } from 'sinon';
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import * as _ from 'lodash';
 
 import * as apiBinder from '../src/api-binder';
diff --git a/test/19-compose-utils.spec.ts b/test/19-compose-utils.spec.ts
index 2e41d675..04f34f10 100644
--- a/test/19-compose-utils.spec.ts
+++ b/test/19-compose-utils.spec.ts
@@ -1,4 +1,4 @@
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import * as ComposeUtils from '../src/compose/utils';
 
 describe('Composition utilities', () =>
diff --git a/test/23-contracts.spec.ts b/test/23-contracts.spec.ts
index ffb58e19..78e613c8 100644
--- a/test/23-contracts.spec.ts
+++ b/test/23-contracts.spec.ts
@@ -1,7 +1,5 @@
 import { assert, expect } from 'chai';
 import { SinonStub, stub } from 'sinon';
-
-import { child_process } from 'mz';
 import * as semver from 'semver';
 
 import * as constants from '../src/lib/constants';
@@ -12,6 +10,7 @@ import {
 } from '../src/lib/contracts';
 import * as osRelease from '../src/lib/os-release';
 import supervisorVersion = require('../src/lib/supervisor-version');
+import * as fsUtils from '../src/lib/fs-utils';
 
 describe('Container contracts', () => {
 	before(() => {
@@ -405,9 +404,10 @@ describe('L4T version detection', () => {
 	let execStub: SinonStub;
 
 	const seedExec = (version: string) => {
-		execStub = stub(child_process, 'exec').returns(
-			Promise.resolve([Buffer.from(version), Buffer.from('')]),
-		);
+		execStub = stub(fsUtils, 'exec').resolves({
+			stdout: Buffer.from(version),
+			stderr: Buffer.from(''),
+		});
 	};
 
 	afterEach(() => {
diff --git a/test/25-journald.spec.ts b/test/25-journald.spec.ts
index b7f356f2..0b24cbda 100644
--- a/test/25-journald.spec.ts
+++ b/test/25-journald.spec.ts
@@ -1,7 +1,7 @@
 import { SinonStub, stub } from 'sinon';
 import constants = require('../src/lib/constants');
 import { spawnJournalctl } from '../src/lib/journald';
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 
 describe('journald', () => {
 	let spawn: SinonStub;
diff --git a/test/27-extlinux-config.spec.ts b/test/27-extlinux-config.spec.ts
index 6b0d6770..690ba03d 100644
--- a/test/27-extlinux-config.spec.ts
+++ b/test/27-extlinux-config.spec.ts
@@ -1,8 +1,8 @@
-import { child_process, fs } from 'mz';
+import { promises as fs } from 'fs';
 import { stripIndent } from 'common-tags';
 import { SinonStub, stub } from 'sinon';
 
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import * as fsUtils from '../src/lib/fs-utils';
 import { Extlinux } from '../src/config/backends/extlinux';
 
@@ -182,7 +182,7 @@ describe('Extlinux Configuration', () => {
 
 	it('sets new config values', async () => {
 		stub(fsUtils, 'writeFileAtomic').resolves();
-		stub(child_process, 'exec').resolves();
+		stub(fsUtils, 'exec').resolves();
 
 		await backend.setBootConfig({
 			fdt: '/boot/mycustomdtb.dtb',
@@ -205,7 +205,7 @@ describe('Extlinux Configuration', () => {
 
 		// Restore stubs
 		(fsUtils.writeFileAtomic as SinonStub).restore();
-		(child_process.exec as SinonStub).restore();
+		(fsUtils.exec as SinonStub).restore();
 	});
 
 	it('only allows supported configuration options', () => {
diff --git a/test/29-append-directive.spec.ts b/test/29-append-directive.spec.ts
index 0dbe3a65..3439f3a8 100644
--- a/test/29-append-directive.spec.ts
+++ b/test/29-append-directive.spec.ts
@@ -1,5 +1,5 @@
 import { AppendDirective } from '../src/config/backends/extlinux-file';
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 
 describe('APPEND directive', () => {
 	const supportedConfigValues = ['isolcpus'];
diff --git a/test/30-fdt-directive.spec.ts b/test/30-fdt-directive.spec.ts
index c3f06348..fb5b6d79 100644
--- a/test/30-fdt-directive.spec.ts
+++ b/test/30-fdt-directive.spec.ts
@@ -1,5 +1,5 @@
 import { FDTDirective } from '../src/config/backends/extlinux-file';
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 
 describe('FDT directive', () => {
 	const directive = new FDTDirective();
diff --git a/test/33-extra-uenv-config.spec.ts b/test/33-extra-uenv-config.spec.ts
index ef252af3..5313c78a 100644
--- a/test/33-extra-uenv-config.spec.ts
+++ b/test/33-extra-uenv-config.spec.ts
@@ -1,8 +1,8 @@
-import { child_process, fs } from 'mz';
+import { promises as fs } from 'fs';
 import { stripIndent } from 'common-tags';
 import { SinonStub, spy, stub } from 'sinon';
 
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import * as fsUtils from '../src/lib/fs-utils';
 import Log from '../src/lib/supervisor-console';
 import { ExtraUEnv } from '../src/config/backends/extra-uEnv';
@@ -67,7 +67,7 @@ describe('extra_uEnv Configuration', () => {
 	});
 
 	it('only matches supported devices', async () => {
-		const existsStub = stub(fs, 'exists');
+		const existsStub = stub(fsUtils, 'exists');
 		for (const device of MATCH_TESTS) {
 			// Test device that has extra_uEnv.txt
 			let hasExtraUEnv = true;
@@ -109,7 +109,7 @@ describe('extra_uEnv Configuration', () => {
 
 	it('sets new config values', async () => {
 		stub(fsUtils, 'writeFileAtomic').resolves();
-		stub(child_process, 'exec').resolves();
+		stub(fsUtils, 'exec').resolves();
 		const logWarningStub = spy(Log, 'warn');
 
 		// This config contains a value set from something else
@@ -138,13 +138,13 @@ describe('extra_uEnv Configuration', () => {
 
 		// Restore stubs
 		(fsUtils.writeFileAtomic as SinonStub).restore();
-		(child_process.exec as SinonStub).restore();
+		(fsUtils.exec as SinonStub).restore();
 		logWarningStub.restore();
 	});
 
 	it('sets new config values containing collections', async () => {
 		stub(fsUtils, 'writeFileAtomic').resolves();
-		stub(child_process, 'exec').resolves();
+		stub(fsUtils, 'exec').resolves();
 		const logWarningStub = spy(Log, 'warn');
 
 		// @ts-ignore accessing private value
@@ -173,7 +173,7 @@ describe('extra_uEnv Configuration', () => {
 
 		// Restore stubs
 		(fsUtils.writeFileAtomic as SinonStub).restore();
-		(child_process.exec as SinonStub).restore();
+		(fsUtils.exec as SinonStub).restore();
 		logWarningStub.restore();
 		// @ts-ignore accessing private value
 		ExtraUEnv.supportedConfigs = previousSupportedConfigs;
diff --git a/test/37-odmdata-config.spec.ts b/test/37-odmdata-config.spec.ts
index 59b96b09..49971170 100644
--- a/test/37-odmdata-config.spec.ts
+++ b/test/37-odmdata-config.spec.ts
@@ -3,7 +3,7 @@ import { promises as fs } from 'fs';
 
 import { resolve } from 'path';
 
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import Log from '../src/lib/supervisor-console';
 import { Odmdata } from '../src/config/backends/odmdata';
 
diff --git a/test/38-sys-info.spec.ts b/test/38-sys-info.spec.ts
index 156b9c22..cc200989 100644
--- a/test/38-sys-info.spec.ts
+++ b/test/38-sys-info.spec.ts
@@ -1,7 +1,7 @@
 import { expect } from 'chai';
 import { stub } from 'sinon';
 import * as systeminformation from 'systeminformation';
-import { fs } from 'mz';
+import { promises as fs } from 'fs';
 
 import * as sysInfo from '../src/lib/system-info';
 
diff --git a/test/39-compose-images.spec.ts b/test/39-compose-images.spec.ts
index 8a63f6c7..7feb9dce 100644
--- a/test/39-compose-images.spec.ts
+++ b/test/39-compose-images.spec.ts
@@ -1,7 +1,7 @@
 import * as _ from 'lodash';
 
 import { docker } from '../src/lib/docker-utils';
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import * as Images from '../src/compose/images';
 import * as mockedDockerode from './lib/mocked-dockerode';
 import * as mockedDatabase from './lib/mocked-database';
diff --git a/test/40-target-state.spec.ts b/test/40-target-state.spec.ts
index 87c19894..367bd8ec 100644
--- a/test/40-target-state.spec.ts
+++ b/test/40-target-state.spec.ts
@@ -4,7 +4,7 @@ import { Promise } from 'bluebird';
 import * as _ from 'lodash';
 import rewire = require('rewire');
 
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import { sleep } from './lib/helpers';
 import * as TargetState from '../src/device-state/target-state';
 import Log from '../src/lib/supervisor-console';
diff --git a/test/41-device-api-v1.spec.ts b/test/41-device-api-v1.spec.ts
index 101e7120..9e0f8a11 100644
--- a/test/41-device-api-v1.spec.ts
+++ b/test/41-device-api-v1.spec.ts
@@ -13,6 +13,7 @@ import * as supertest from 'supertest';
 import * as path from 'path';
 import { promises as fs } from 'fs';
 
+import { exists, unlinkAll } from '../src/lib/fs-utils';
 import * as appMock from './lib/application-state-mock';
 import * as mockedDockerode from './lib/mocked-dockerode';
 import mockedAPI = require('./lib/mocked-device-api');
@@ -826,7 +827,7 @@ describe('SupervisorAPI [V1 Endpoints]', () => {
 			});
 
 			it('returns current host config (hostname only)', async () => {
-				await Promise.all([fs.unlink(redsocksPath), fs.unlink(noProxyPath)]);
+				await unlinkAll(redsocksPath, noProxyPath);
 
 				await request
 					.get('/v1/device/host-config')
@@ -839,7 +840,7 @@ describe('SupervisorAPI [V1 Endpoints]', () => {
 			});
 
 			it('errors if no hostname file exists', async () => {
-				await fs.unlink(hostnamePath);
+				await unlinkAll(hostnamePath);
 
 				await request
 					.get('/v1/device/host-config')
@@ -896,7 +897,7 @@ describe('SupervisorAPI [V1 Endpoints]', () => {
 			});
 
 			it('updates the hostname with provided string if string is not empty', async () => {
-				await Promise.all([fs.unlink(redsocksPath), fs.unlink(noProxyPath)]);
+				await unlinkAll(redsocksPath, noProxyPath);
 
 				const patchBody = { network: { hostname: 'newdevice' } };
 
@@ -924,8 +925,7 @@ describe('SupervisorAPI [V1 Endpoints]', () => {
 			});
 
 			it('updates hostname to first 7 digits of device uuid when sent invalid hostname', async () => {
-				await Promise.all([fs.unlink(redsocksPath), fs.unlink(noProxyPath)]);
-
+				await unlinkAll(redsocksPath, noProxyPath);
 				await request
 					.patch('/v1/device/host-config')
 					.send({ network: { hostname: '' } })
@@ -965,8 +965,8 @@ describe('SupervisorAPI [V1 Endpoints]', () => {
 					.then(async (response) => {
 						validatePatchResponse(response);
 
-						expect(fs.stat(redsocksPath)).to.be.rejected;
-						expect(fs.stat(noProxyPath)).to.be.rejected;
+						expect(await exists(redsocksPath)).to.be.false;
+						expect(await exists(noProxyPath)).to.be.false;
 					});
 
 				expect(restartServiceSpy.callCount).to.equal(2);
diff --git a/test/43-splash-image.spec.ts b/test/43-splash-image.spec.ts
index 841c80d9..b2dc3583 100644
--- a/test/43-splash-image.spec.ts
+++ b/test/43-splash-image.spec.ts
@@ -1,7 +1,7 @@
-import { fs, child_process } from 'mz';
+import { promises as fs } from 'fs';
 import { SinonStub, stub } from 'sinon';
 
-import { expect } from './lib/chai-config';
+import { expect } from 'chai';
 import * as fsUtils from '../src/lib/fs-utils';
 import { SplashImage } from '../src/config/backends/splash-image';
 import log from '../src/lib/supervisor-console';
@@ -20,27 +20,27 @@ describe('Splash image configuration', () => {
 	beforeEach(() => {
 		// Setup stubs
 		writeFileAtomicStub = stub(fsUtils, 'writeFileAtomic').resolves();
-		stub(child_process, 'exec').resolves();
+		stub(fsUtils, 'exec').resolves();
 		readFileStub = stub(fs, 'readFile').resolves(
 			Buffer.from(logo, 'base64') as any,
 		);
 		readFileStub
 			.withArgs('test/data/mnt/boot/splash/balena-logo-default.png')
 			.resolves(Buffer.from(defaultLogo, 'base64') as any);
-		readDirStub = stub(fs, 'readdir').resolves(['balena-logo.png']);
+		readDirStub = stub(fs, 'readdir').resolves(['balena-logo.png'] as any);
 	});
 
 	afterEach(() => {
 		// Restore stubs
 		writeFileAtomicStub.restore();
-		(child_process.exec as SinonStub).restore();
+		(fsUtils.exec as SinonStub).restore();
 		readFileStub.restore();
 		readDirStub.restore();
 	});
 
 	describe('initialise', () => {
 		it('should make a copy of the existing boot image on initialise if not yet created', async () => {
-			stub(fs, 'exists').resolves(false);
+			stub(fsUtils, 'exists').resolves(false);
 
 			// Do the initialization
 			await backend.initialise();
@@ -55,25 +55,25 @@ describe('Splash image configuration', () => {
 				Buffer.from(logo, 'base64'),
 			);
 
-			(fs.exists as SinonStub).restore();
+			(fsUtils.exists as SinonStub).restore();
 		});
 
 		it('should skip initialization if the default image already exists', async () => {
-			stub(fs, 'exists').resolves(true);
+			stub(fsUtils, 'exists').resolves(true);
 
 			// Do the initialization
 			await backend.initialise();
 
-			expect(fs.exists).to.be.calledOnceWith(
+			expect(fsUtils.exists).to.be.calledOnceWith(
 				'test/data/mnt/boot/splash/balena-logo-default.png',
 			);
 			expect(fs.readFile).to.not.have.been.called;
 
-			(fs.exists as SinonStub).restore();
+			(fsUtils.exists as SinonStub).restore();
 		});
 
 		it('should fail initialization if there is no default image on the device', async () => {
-			stub(fs, 'exists').resolves(false);
+			stub(fsUtils, 'exists').resolves(false);
 			readDirStub.resolves([]);
 			readFileStub.rejects();
 			stub(log, 'warn');
diff --git a/test/lib/mocked-device-api.ts b/test/lib/mocked-device-api.ts
index 03731a20..9ac2eeca 100644
--- a/test/lib/mocked-device-api.ts
+++ b/test/lib/mocked-device-api.ts
@@ -1,8 +1,8 @@
 import * as _ from 'lodash';
 import { Router } from 'express';
-import { fs } from 'mz';
 import rewire = require('rewire');
 
+import { unlinkAll } from '../../src/lib/fs-utils';
 import * as applicationManager from '../../src/compose/application-manager';
 import * as networkManager from '../../src/compose/network-manager';
 import * as serviceManager from '../../src/compose/service-manager';
@@ -149,12 +149,8 @@ async function create(): Promise<SupervisorAPI> {
 }
 
 async function cleanUp(): Promise<void> {
-	try {
-		// clean up test data
-		await fs.unlink(DB_PATH);
-	} catch (e) {
-		/* noop */
-	}
+	// Clean up test data
+	await unlinkAll(DB_PATH);
 	// Restore created SinonStubs
 	return restoreStubs();
 }
diff --git a/test/lib/mocked-iptables.ts b/test/lib/mocked-iptables.ts
index c867e1c4..38c1bd4b 100644
--- a/test/lib/mocked-iptables.ts
+++ b/test/lib/mocked-iptables.ts
@@ -1,7 +1,7 @@
 import _ = require('lodash');
 import { expect } from 'chai';
 import { stub } from 'sinon';
-import { child_process } from 'mz';
+import * as childProcess from 'child_process';
 
 import * as firewall from '../../src/lib/firewall';
 import * as iptables from '../../src/lib/iptables';
@@ -130,7 +130,7 @@ export const whilstMocked = async (
 ) => {
 	const getOriginalDefaultRuleAdaptor = iptables.getDefaultRuleAdaptor;
 
-	const spawnStub = stub(child_process, 'spawn').callsFake(() => {
+	const spawnStub = stub(childProcess, 'spawn').callsFake(() => {
 		const fakeProc = new EventEmitter();
 		(fakeProc as any).stdout = new EventEmitter();
 
diff --git a/test/mocha.opts b/test/mocha.opts
index f447b09c..f383576e 100644
--- a/test/mocha.opts
+++ b/test/mocha.opts
@@ -1,3 +1,3 @@
 --exit
 --timeout 30000
-build/test/**/*.js
+build/test/**/*.spec.js
diff --git a/test/compose/network.spec.ts b/test/src/compose/network.spec.ts
similarity index 98%
rename from test/compose/network.spec.ts
rename to test/src/compose/network.spec.ts
index 462f8b58..3b497ed1 100644
--- a/test/compose/network.spec.ts
+++ b/test/src/compose/network.spec.ts
@@ -1,7 +1,6 @@
-import ChaiConfig = require('../lib/chai-config');
-const { expect } = ChaiConfig;
+import { expect } from 'chai';
 
-import { Network } from '../../src/compose/network';
+import { Network } from '../../../src/compose/network';
 import { NetworkInspectInfo } from 'dockerode';
 
 describe('compose/network', () => {
diff --git a/test/src/lib/fs-utils.spec.ts b/test/src/lib/fs-utils.spec.ts
new file mode 100644
index 00000000..34891734
--- /dev/null
+++ b/test/src/lib/fs-utils.spec.ts
@@ -0,0 +1,157 @@
+import { expect } from 'chai';
+import * as path from 'path';
+import { promises as fs } from 'fs';
+import { spy, SinonSpy } from 'sinon';
+import mock = require('mock-fs');
+
+import * as fsUtils from '../../../src/lib/fs-utils';
+import { rootMountPoint } from '../../../src/lib/constants';
+
+describe('lib/fs-utils', () => {
+	const testFileName1 = 'file.1';
+	const testFileName2 = 'file.2';
+	const testFile1 = path.join(rootMountPoint, testFileName1);
+	const testFile2 = path.join(rootMountPoint, testFileName2);
+
+	const mockFs = () => {
+		mock({
+			[testFile1]: 'foo',
+			[testFile2]: 'bar',
+		});
+	};
+
+	const unmockFs = () => {
+		mock.restore();
+	};
+
+	describe('writeAndSyncFile', () => {
+		before(mockFs);
+		after(unmockFs);
+
+		it('should write and sync string data', async () => {
+			await fsUtils.writeAndSyncFile(testFile1, 'foo bar');
+			expect(await fs.readFile(testFile1, 'utf-8')).to.equal('foo bar');
+		});
+
+		it('should write and sync buffers', async () => {
+			await fsUtils.writeAndSyncFile(testFile1, Buffer.from('bar foo'));
+			expect(await fs.readFile(testFile1, 'utf-8')).to.equal('bar foo');
+		});
+	});
+
+	describe('writeFileAtomic', () => {
+		before(() => {
+			spy(fs, 'rename');
+			mockFs();
+		});
+
+		after(() => {
+			(fs.rename as SinonSpy).restore();
+			unmockFs();
+		});
+
+		it('should write string data atomically', async () => {
+			await fsUtils.writeFileAtomic(testFile1, 'foo baz');
+			expect(await fs.readFile(testFile1, 'utf-8')).to.equal('foo baz');
+			expect(fs.rename).to.have.been.calledWith(`${testFile1}.new`, testFile1);
+		});
+
+		it('should write buffer data atomically', async () => {
+			await fsUtils.writeFileAtomic(testFile1, 'baz foo');
+			expect(await fs.readFile(testFile1, 'utf-8')).to.equal('baz foo');
+			expect(fs.rename).to.have.been.calledWith(`${testFile1}.new`, testFile1);
+		});
+	});
+
+	describe('safeRename', () => {
+		beforeEach(mockFs);
+		afterEach(unmockFs);
+
+		it('should rename a file', async () => {
+			await fsUtils.safeRename(testFile1, testFile1 + 'rename');
+			const dirContents = await fs.readdir(rootMountPoint);
+			expect(dirContents).to.have.length(2);
+			expect(dirContents).to.not.include(testFileName1);
+			expect(dirContents).to.include(testFileName1 + 'rename');
+		});
+
+		it('should replace an existing file', async () => {
+			await fsUtils.safeRename(testFile1, testFile2);
+			const dirContents = await fs.readdir(rootMountPoint);
+			expect(dirContents).to.have.length(1);
+			expect(dirContents).to.include(testFileName2);
+			expect(dirContents).to.not.include(testFileName1);
+		});
+	});
+
+	/**
+	 * TODO: Un-skip this test after all fs tests that write to a test file system use
+	 * mock-fs instead. Hypothesis: exists isn't handling the relative directory it's
+	 * being passed well. When all unit tests use mock-fs, we can set process.env.ROOT_MOUNTPOINT
+	 * to `/mnt/root` so we can have an absolute path in all these tests.
+	 */
+	describe.skip('exists', () => {
+		before(mockFs);
+		after(unmockFs);
+
+		it('should return whether a file exists', async () => {
+			expect(await fsUtils.exists(testFile1)).to.be.true;
+			await fs.unlink(testFile1).catch(() => {
+				/* noop */
+			});
+			expect(await fsUtils.exists(testFile1)).to.be.false;
+		});
+	});
+
+	describe('pathExistsOnHost', () => {
+		before(mockFs);
+		after(unmockFs);
+
+		it('should return whether a file exists in host OS fs', async () => {
+			expect(await fsUtils.pathExistsOnHost(testFileName1)).to.be.true;
+			await fs.unlink(testFile1);
+			expect(await fsUtils.pathExistsOnHost(testFileName1)).to.be.false;
+		});
+	});
+
+	describe('mkdirp', () => {
+		before(mockFs);
+		after(unmockFs);
+
+		it('should recursively create directories', async () => {
+			await fsUtils.mkdirp(
+				path.join(rootMountPoint, 'test1', 'test2', 'test3'),
+			);
+			expect(() =>
+				fs.readdir(path.join(rootMountPoint, 'test1', 'test2', 'test3')),
+			).to.not.throw();
+		});
+	});
+
+	describe('unlinkAll', () => {
+		beforeEach(mockFs);
+		afterEach(unmockFs);
+
+		it('should unlink a single file', async () => {
+			await fsUtils.unlinkAll(testFile1);
+			expect(await fs.readdir(rootMountPoint)).to.not.include(testFileName1);
+		});
+
+		it('should unlink multiple files', async () => {
+			await fsUtils.unlinkAll(testFile1, testFile2);
+			expect(await fs.readdir(rootMountPoint)).to.have.length(0);
+		});
+	});
+
+	describe('getPathOnHost', () => {
+		before(mockFs);
+		after(unmockFs);
+
+		it("should return the paths of one or more files as they exist on host OS's root", async () => {
+			expect(fsUtils.getPathOnHost(testFileName1)).to.deep.equal([testFile1]);
+			expect(
+				fsUtils.getPathOnHost(...[testFileName1, testFileName2]),
+			).to.deep.equal([testFile1, testFile2]);
+		});
+	});
+});