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Mullvad VPN uses a comprehensive testing strategy that includes unit tests, integration tests, end-to-end (e2e) tests, and UI tests across all platforms. This ensures reliability and quality across the desktop, Android, and iOS applications.

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Test Types

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Unit Tests

Unit tests verify individual components and functions in isolation.

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Rust Unit Tests

Rust unit tests are embedded within the source code using Rust’s built-in testing framework. Run all Rust unit tests: 
cargo test --workspace
Run tests for a specific crate: 
cargo test -p mullvad-daemon
cargo test -p mullvad-api
cargo test -p talpid-core
Run with test output visible: 
cargo test -- --nocapture
Test dependencies are configured in Cargo.toml workspaces with common testing libraries like proptest for property-based testing and insta for snapshot testing.

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Desktop Unit Tests (JavaScript/TypeScript)

Unit tests for the desktop application use Vitest as the test runner. Run desktop unit tests: 
cd desktop/packages/mullvad-vpn
npm test
Unit tests are located in desktop/packages/mullvad-vpn/test/unit/ and test utilities, helpers, and business logic:
  • Account validation (account-number.spec.ts)
  • Date and time helpers (date-helper.spec.ts)
  • IP address utilities (ip.spec.ts)
  • Tunnel state management (tunnel-state.spec.ts)
  • Notification logic (notification-evaluation.spec.ts)
Tests use Vitest with the following configuration in package.json: 
"test": "cross-env NODE_ENV=test vitest test/unit"

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Android Unit Tests

Android unit tests use JUnit5 and are located in module-specific test/ directories. Run Android unit tests: 
cd android
./gradlew testDebugUnitTest
Run tests for a specific module: 
./gradlew :app:testDebugUnitTest
./gradlew :lib:billing:testDebugUnitTest
Android test configuration in app/build.gradle.kts: 
testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"

testOptions {
    unitTests.all { test ->
        test.testLogging {
            test.outputs.upToDateWhen { false }
        }
    }
}

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iOS Unit Tests

iOS unit tests use XCTest and are organized into test targets. Run iOS tests via Xcode: 
xcodebuild test -project ios/MullvadVPN.xcodeproj -scheme MullvadVPN
iOS test modules include:
  • MullvadRESTTests - API and REST client tests
  • MullvadRustRuntimeTests - Rust FFI integration tests
  • MullvadPostQuantumTests - Post-quantum cryptography tests

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Integration Tests

Integration tests verify interactions between components and with external services.

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Rust Integration Tests

The test workspace (test/ directory) contains a dedicated testing framework for end-to-end integration tests. Test workspace structure:
  • test-manager - Client that runs on the host and orchestrates tests
  • test-runner - Server that runs in guest VMs and provides RPC interface
  • test-rpc - Shared RPC interface and types
  • connection-checker - Network connectivity validation
  • socks-server - SOCKS proxy for testing
Build the test runner: 
# Linux
./scripts/container-run.sh ./scripts/build/test-runner.sh linux

# macOS
./scripts/build/test-runner.sh macos

# Windows (cross-compile from Linux)
./scripts/container-run.sh ./scripts/build/test-runner.sh windows
Run integration tests: 
cd test
cargo run --bin test-manager run-tests --vm <vm-name> \
    --display \
    --account <account-number> \
    --app-package <version>

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End-to-End Tests

End-to-end tests verify complete user workflows and system behavior.

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Desktop E2E Tests

Desktop e2e tests use Playwright and are written in TypeScript. Test categories:
  • Mocked tests (test/e2e/mocked/) - Run with mocked backend APIs
  • Installed tests (test/e2e/installed/) - Run against installed application
Run mocked e2e tests: 
cd desktop/packages/mullvad-vpn
npm run e2e
Run without rebuilding: 
npm run e2e:no-build
Run installed app tests: 
npm run e2e:sequential
Update test snapshots: 
npm run e2e:update-snapshots
Playwright configuration is in playwright.config.ts and test/e2e/installed/playwright.config.ts.

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Android E2E Tests

Android e2e tests are instrumented tests that run on real devices or emulators. Run Android e2e tests: 
cd android
./gradlew :test:e2e:connectedDebugAndroidTest \
    -Pmullvad.test.e2e.prod.accountNumber.valid=<account> \
    -Pmullvad.test.e2e.prod.accountNumber.invalid=<invalid-account>
Android e2e tests require:
  • Valid Mullvad account number for authentication tests
  • Invalid account number for negative test cases
  • Access to Mullvad public infrastructure and APIs
Test artifacts are stored in /sdcard/Download/test-attachments on the test device.

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UI/Graphical Tests

UI tests verify visual and interactive elements of the application.

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Desktop UI Tests

Desktop UI tests are written in TypeScript using Playwright and located in desktop/packages/mullvad-vpn/test/e2e/. Key test areas:
  • Login flows (login.spec.ts)
  • Account expiry (account-expiry.spec.ts)
  • Connection states (main.spec.ts)
  • Settings screens (settings.spec.ts)
  • Location selection (select-location/)
  • Notifications (notifications.spec.ts)
  • Split tunneling (split-tunneling.spec.ts)
Build test executable: 
cd desktop/packages/mullvad-vpn
npm run build-test-executable
UI tests can be invoked from Rust integration tests: 
test_manager::tests::ui::run_test(&rpc, &["gui-test.spec"]).await.unwrap()

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Test Infrastructure

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Test Manager Framework

The test-manager provides a framework for writing integration tests: 
#[test_function]
pub async fn test(
    rpc: ServiceClient,
    mut mullvad_client: mullvad_management_interface::MullvadProxyClient,
) -> Result<(), Error> {
    // Test implementation
    Ok(())
}
Test modules in test-manager/src/tests/:
  • account.rs - Account management tests
  • config.rs - Configuration tests
  • dns.rs - DNS functionality tests
  • tunnel.rs - VPN tunnel tests
  • tunnel_state.rs - Tunnel state management
  • access_methods.rs - API access method tests
  • audits/ - Security audit verification tests

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CI/CD Testing

Tests run automatically in GitHub Actions: Desktop tests: 
cd desktop && npm run test --workspaces --if-present
Android tests: 
./gradlew testDebugUnitTest
./gradlew connectedDebugAndroidTest
Rust tests: 
cargo test --workspace

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Running All Tests

To run all tests across the project: 
# Rust tests
cargo test --workspace

# Desktop tests
cd desktop
npm run test --workspaces --if-present

# Desktop e2e tests
cd packages/mullvad-vpn
npm run e2e

# Android tests
cd ../../android
./gradlew testDebugUnitTest

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Test Configuration

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Workspace Configuration

The root Cargo.toml defines workspace-wide test dependencies: 
[workspace.dependencies]
insta = { version = "1.42", features = ["yaml"] }
proptest = "1.9"

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Linting and Code Quality

Tests must pass the same linting rules as production code: 
# Rust
cargo clippy --all-targets --all-features

# Desktop
cd desktop && npm run lint

# Android
cd android && ./gradlew lint

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Best Practices

  1. Write tests alongside code - Unit tests should be close to the code they test
  2. Use descriptive test names - Test names should clearly indicate what is being tested
  3. Test edge cases - Include tests for error conditions and boundary cases
  4. Keep tests fast - Unit tests should run quickly; save longer tests for integration
  5. Mock external dependencies - Use mocked backends for faster and more reliable tests
  6. Use test fixtures - Share common test setup code across tests
  7. Test public interfaces - Focus on testing public APIs rather than internal implementation

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