Running tests for WebAssembly

To run tests for WebAssembly, install a Swift SDK for WebAssembly by following these instructions.

In Swift 6.3 and later, running swift test --swift-sdk <wasm_swift_sdk_id> builds and runs your tests. Use jq to extract the Swift SDK ID automatically to build and test in a single command:

swift test --swift-sdk \
  "$(swiftc -print-target-info | jq -r '.swiftCompilerTag')_wasm"

Build and Test WebAssembly separately

Prior to Swift 6.3, swift test doesn't support --swift-sdk option to indicate the WebAssembly environment to use for tests. In this case, building tests and running them are two separate steps. To build tests for WebAssembly, use the following command:

swift build \
  --swift-sdk "$(swiftc -print-target-info | jq -r '.swiftCompilerTag')_wasm" \
  --build-tests

After building tests, you can run them using a WASI-compliant WebAssembly runtime such as WasmKit. WasmKit is included in the Swift toolchain for Linux and macOS for Swift 6.2 and later. Download and install an open-source release toolchain from swift.org to get a toolchain that includes WasmKit.

To run the rests you built previously using the WasmKit runtime, use the following command, replacing {YOURPACKAGE} with the name of your package:

wasmkit run .build/debug/{YOURPACKAGE}PackageTests.wasm \
  --testing-library swift-testing

Most WebAssembly runtimes forward trailing arguments to the WebAssembly program, so you can pass command-line options of the testing library. For example, to list all tests and filter them by name, use the following commands:

wasmkit run .build/debug/{YOURPACKAGE}PackageTests.wasm list \
  --testing-library swift-testing
wasmkit run .build/debug/{YOURPACKAGE}PackageTests.wasm \
  --testing-library swift-testing --filter "FoodTruckTests.foodTruckExists"