ble_device_simulator

Build and test Bluetooth LE health and fitness apps without hardware.

Simulated heart-rate straps, blood pressure cuffs, thermometers, pulse oximeters, power meters, foot pods and scales that send the exact bytes real devices send, following the Bluetooth SIG specs.

• Write tests for BLE code: in CI, on every developer's laptop, with no device in a drawer somewhere
• Reproduce edge cases on demand: a slipped strap, a fever, low oxygen, a flat battery, a dropped connection
• Deterministic: the same seed always gives the same readings, and simulated time only moves when you say so
• Real bytes: every notification is checked in this package's tests by parsing it with ble_gatt_parser
• Pure Dart: works in Flutter widget tests, plain Dart tests and on the web

final strap = SimulatedHeartRateMonitor()..connect();

strap.notifications(GattCharacteristicIds.heartRateMeasurement).listen((bytes) {
  print(GattParser.parse('2a37', bytes)); // HeartRateMeasurement(bpm: 74, ...)
});

strap.tick();               // one second of simulated time
strap.skinContact = false;  // the strap slips off
strap.batteryLevel = 5;     // battery warning
strap.disconnect();         // out of range

Install

dart pub add dev:ble_device_simulator

Add it as a regular dependency instead if you also want simulated devices in a demo or debug build.

Devices

Class	Service	Sends	Edge cases
SimulatedHeartRateMonitor	Heart Rate (0x180D)	bpm and RR-intervals every second	skinContact = false, custom bpm range
SimulatedBloodPressureMonitor	Blood Pressure (0x1810)	A reading when you call measure()	Custom systolic and diastolic ranges
SimulatedThermometer	Health Thermometer (0x1809)	Ear temperature every second	fever = true
SimulatedPulseOximeter	Pulse Oximeter (0x1822)	SpO2, pulse and perfusion index	lowOxygen = true
SimulatedPowerMeter	Cycling Power (0x1818)	Watts and crank revolutions, for cadence	Custom power and rpm ranges
SimulatedRunningPod	Running Speed and Cadence (0x1814)	Speed, cadence and distance	Custom speed range
SimulatedWeightScale	Weight Scale (0x181D)	A measurement when you call weigh()	Optional BMI and height

Every device also has Device Information (manufacturer, model, firmware) and Battery (0x180F), with read(), connect(), disconnect(), connectionState, batteryLevel and services.

Testing a Flutter app

Put a small interface between your app and your BLE plugin, and use the simulator in tests:

abstract class HeartRateSource {
  Stream<List<int>> get measurements;
}

/// In the app: flutter_blue_plus, flutter_reactive_ble or your own plugin.
class BluetoothHeartRateSource implements HeartRateSource {
  BluetoothHeartRateSource(this.characteristic);
  final BluetoothCharacteristic characteristic;

  @override
  Stream<List<int>> get measurements => characteristic.onValueReceived;
}

/// In tests and demos.
class SimulatedHeartRateSource implements HeartRateSource {
  SimulatedHeartRateSource(this.device);
  final SimulatedHeartRateMonitor device;

  @override
  Stream<List<int>> get measurements =>
      device.notifications(GattCharacteristicIds.heartRateMeasurement);
}

testWidgets('shows a warning when the strap slips', (tester) async {
  final strap = SimulatedHeartRateMonitor()..connect();
  await tester.pumpWidget(HeartRateScreen(source: SimulatedHeartRateSource(strap)));

  strap.tick();
  await tester.pump();
  expect(find.textContaining('bpm'), findsOneWidget);

  strap.skinContact = false;
  strap.tick();
  await tester.pump();
  expect(find.text('Check your strap'), findsOneWidget);
});

Time

Simulated time only moves when you call tick(), which advances one second and sends that second's notifications synchronously. That keeps tests fast and predictable. For demos, start(interval: ...) ticks on a timer: a shorter interval runs simulated time faster. Call stop() or dispose() when you're done.

Encoders

The devices are built on GattEncoder, which you can also use directly to build any measurement by hand:

final bytes = GattEncoder.bloodPressure(
  systolic: 142,
  diastolic: 91,
  pulseRate: 88,
  timestamp: DateTime(2026, 1, 1, 8),
);

It covers heart rate, blood pressure, temperature, pulse oximetry, weight, cycling speed and cadence, cycling power, running speed and cadence, battery level and strings, plus the IEEE 11073 SFLOAT and FLOAT number formats.

About the author

Built by Chandra ObulaReddy, a Flutter architect who has shipped Bluetooth LE and wearable integrations for safety, healthcare and fitness products. See also ble_gatt_parser, which parses the bytes these devices send.