diff --git a/lib/device.js b/lib/device.js
index 7fd719b..a814e28 100644
--- a/lib/device.js
+++ b/lib/device.js
@@ -565,7 +565,11 @@ class DeviceManager {
 		} else {
 			platforms = this._devicePool;
 		}
-		const devs = platforms.get(platform.id);
+		let id = platform.id;
+		if (platform.mixed && Array.from(platforms.keys()).length === 1) {
+			id = Array.from(platforms.keys())[0];
+		}
+		const devs = platforms.get(id);
 		if (!devs || !devs.length) {
 			throw new Error('No devices available for the target platform');
 		}
@@ -756,6 +760,17 @@ class DeviceManager {
 			dev.setAttached(attached);
 		}
 	}
+
+	getPlatformsForFixtures(fixtures) {
+		const platforms = [];
+		for (const f of fixtures) {
+			const fixture = this._fixtures.get(f.name);
+			if (fixture) {
+				platforms.push(... fixture.keys());
+			}
+		}
+		return Array.from(new Set(platforms));
+	}
 }
 
 module.exports = {
diff --git a/lib/runner.js b/lib/runner.js
index 8a32a84..5103fa8 100644
--- a/lib/runner.js
+++ b/lib/runner.js
@@ -2,7 +2,7 @@ const { PlatformSuite } = require('./suite');
 const { DeviceManager } = require('./device');
 const { ApiClient } = require('./api');
 const { Builder } = require('./build');
-const { platformsForTag, isKnownPlatformTag, PLATFORMS, PLATFORM_TAGS } = require('./platform');
+const { platformsForTag, isKnownPlatformTag, PLATFORMS, PLATFORM_TAGS, Platform } = require('./platform');
 const { RunMode, OutputFormat, config, APP_NAME } = require('./config');
 const { findTestName, shortenRight } = require('./util');
 const { InternalError, isInternalError } = require('./error');
@@ -185,8 +185,6 @@ class Runner {
 	}
 
 	async _run() {
-		this._log.verbose('Generating test matrix');
-		this._initTestMatrix();
 		this._log.verbose('Initializing API client');
 		this._apiClient = new ApiClient({
 			log: this._log
@@ -198,6 +196,8 @@ class Runner {
 			log: this._log
 		});
 		await this._devMgr.init(this._enabledPlatforms);
+		this._log.verbose('Generating test matrix');
+		await this._initTestMatrix();
 		// Initialize the runner's context
 		const ctx = this._mocha.suite.ctx;
 		ctx.particle = {
@@ -401,7 +401,7 @@ class Runner {
 		runner.once(MochaRunner.constants.EVENT_RUN_END, runEnd);
 	}
 
-	_initTestMatrix() {
+	async _initTestMatrix() {
 		const suites = [];
 		const rootSuite = this._mocha.suite;
 		for (const srcSuite of rootSuite.suites) {
@@ -411,8 +411,26 @@ class Runner {
 			}
 			const file = particle.file;
 			const newSuite = srcSuite.clone(); // Doesn't copy tests and hooks
+			let platformsByFixture = this._devMgr.getPlatformsForFixtures(particle.fixtures);
+			let platforms = particle.platforms;
+			if (platformsByFixture && platformsByFixture.length > 1) {
+				// Mixed platforms
+				platformsByFixture = platforms.filter((v) => platformsByFixture.includes(v.id));
+				platforms = platformsByFixture;
+				let fakeId = 0;
+				const fakeName = platforms.map((v) => v.name).join('/');
+				const fakeDisplayName = platforms.map((v) => v.displayName).join(' / ');
+				const fakeTags = [... platforms.map((v) => v.tags)].flat(1);
+				for (let i = 0; i < platforms.length; i++) {
+					fakeId += platforms[i].id * (100 ** (i));
+				}
+				platforms = [new Platform({ id: fakeId, name: fakeName, displayName: fakeDisplayName, tags: fakeTags })];
+				// FIXME
+				platforms[0].mixed = true;
+				platforms[0].platforms = platformsByFixture;
+			}
 			// Create a nested suite for each platform
-			for (const platform of particle.platforms) {
+			for (const platform of platforms) {
 				const platformSuite = MochaSuite.create(newSuite, platform.name);
 				platformSuite.particle = {
 					platform,
diff --git a/lib/suite.js b/lib/suite.js
index 7b22626..bc85ccc 100644
--- a/lib/suite.js
+++ b/lib/suite.js
@@ -161,10 +161,9 @@ class PlatformSuite {
 		this._ctx.addDeviceTests(this._suite, tests);
 	}
 
-	async _flashApps() {
+	async _flashAppForPlatform(platform) {
 		const particle = this._suite.particle;
 		const suiteDir = path.dirname(particle.file);
-		const platform = particle.platform;
 		const apps = new Map();
 		// Find precompiled binaries
 		if (this._ctx.binaryDir) {
@@ -208,13 +207,15 @@ class PlatformSuite {
 			if (!app) {
 				throw new Error(`Application not found: ${appName}`);
 			}
-			devApps.push({ dev, app });
+			if (dev.platform.id === platform.id) {
+				devApps.push({ dev, app });
+			}
 		}
 		// Build applications
 		for (const devApp of devApps) {
 			const app = devApp.app;
 			if (app.build) {
-				this._log.verbose(`Building application: ${app.path}`);
+				this._log.verbose(`Building application for ${platform.name}: ${app.path}`);
 				app.path = await this._ctx.builder.buildApp({ appDir: app.path, platform });
 				app.build = false;
 			}
@@ -248,6 +249,17 @@ class PlatformSuite {
 		}
 	}
 
+	async _flashApps() {
+		const particle = this._suite.particle;
+		if (!particle.platform.mixed) {
+			return this._flashAppForPlatform(particle.platform);
+		} else {
+			for (const platform of particle.platform.platforms) {
+				await this._flashAppForPlatform(platform);
+			}
+		}
+	}
+
 	async _initDevices() {
 		this._ctx.devices = [];
 		this._ctx.fixtures = new Map();