A sample app that implements an audio recording flow in SwiftUI: start, pause, and resume a recording while a timer tracks the elapsed time, then send the recording for (simulated) processing.

Context

This sample app was created for a technical interview for a senior Mobile (iOS + Android) engineer role at Attendi, a Dutch health-tech company that makes voice-driven reporting software for healthcare professionals, based on a given set of requirements.

Demo

▶️ Watch the sample (iOS) app in action!

Requirements

Requirement	Version
Xcode	26 or later
Swift	6.3
Platforms	iOS/macOS/visionOS 26

Project structure

The project separates the app shell from the feature code, which lives in a local Swift package:

Attendi/
├── Attendi.xcodeproj
├── Apps/
│   └── Attendi/                     # The app target (thin shell)
│       ├── AttendiApp.swift         # The @main entry point
│       ├── ContentView.swift        # The root view, hosting the Recording feature
│       └── Assets.xcassets
└── Packages/
    └── Features/                    # Local Swift package with the feature code
        ├── Package.swift
        ├── Sources/
        │   └── Recording/           # The Recording feature target
        │       ├── RecordingView.swift
        │       ├── RecordingViewModel.swift
        │       ├── RecordingButtonStyle.swift
        │       ├── RecordingService.swift
        │       ├── TranscribingService.swift
        │       └── Images.xcassets  # Record, pause, and send icons
        └── Tests/
            ├── Recording/
            │   └── RecordingViewModelTests.swift
            └── Features.xctestplan

The app target only depends on the Features package and renders its public RecordingView view; all recording logic and UI live in the package's Recording target.

The Recording feature

State machine

The flow is modeled as a state machine in RecordingView.Model, an @Observable, @MainActor view model:

State	Meaning
`notRecording`	Idle; no recording in progress.
`recording`	A recording is in progress and the timer is ticking.
`paused`	The recording is paused; it can be resumed or sent.
`processing`	The sent recording is being processed.

The main button starts, pauses, and resumes a recording. While paused, a send button appears; pressing it moves the flow into processing (currently simulated with a delay) before returning to idle.

Timer

While recording, an async task increments the elapsed seconds once per second — pausing stops it, resuming continues it, and a new recording resets it. The view formats the count as mm:ss and animates digit changes with a numeric text content transition.

Views

RecordingView — the public entry point of the feature. It renders the timer label and the control buttons for the model's current state, and forwards state changes back to the model.
RecordingButtonStyle — a custom ButtonStyle used by the controls: the label sits on a padded, circular red background, shrinks while pressed, and dims while disabled. The label and its padding scale with Dynamic Type via @ScaledMetric, and an invertStyle flag controls whether the label's color scheme is inverted for contrast.

Services

The actual recording work is abstracted behind two protocols, injected into RecordingView at initialization and attached to its view model:

RecordingService — captures the audio from a microphone, with throwing async start, pause, resume, and stop methods; stop returns the captured audio.
TranscribingService — transcribes the captured audio into text through a throwing async transcribe method; the view model stores the result once processing finishes.

The default SimulatedRecordingService and SimulatedTranscribingService fake the work (the latter with a two-second delay and a dummy transcription); the unit tests inject fast mocks, and real backends can be plugged in the same way without touching the feature's state machine. When either service fails, the view model falls back to the not-recording state.

Testing

The view model is covered by Swift Testing suites in RecordingViewModelTests.swift, grouped with nested @Suite types (initial state, button presses, computed properties, timer, and processing). The state-dependent behaviors are exercised with parameterized tests across all four states.

Run the tests with the Features scheme in Xcode (⌘U), or from the command line:

xcodebuild test -scheme Features -destination 'platform=iOS'

Tooling

.swift-format — configuration for Apple's swift-format, used by Xcode's built-in formatter (4-space indentation, 200-column lines).