Testing¶

What there is¶

Location	What it tests	How to run
tests/uniffi/*	Generated bindings, one fixture per feature, on every target	./gradlew :tests:uniffi:<name>:allTests
tests/runtime	The runtime through generated bindings	./gradlew :tests:runtime:allTests
runtime/src/*Test	The runtime itself, including Android host and device tests	./gradlew :runtime:allTests
examples/*	That the examples build and their tests pass	./gradlew :examples:<name>:allTests
build-logic/gradle-plugin/src/test	Plugin unit tests	./gradlew -p build-logic check
cargo test	The Rust crates in the workspace, including the bindgen	cargo test

CI (.github/workflows/run-tests.yml) runs cargo test, ./gradlew -p build-logic check and ./gradlew build on Linux. It cross-compiles for Android, Windows (MinGW) and aarch64 Linux. Apple targets are not built in CI. Run them locally on a Mac before merging changes to native code.

Fixtures¶

Most fixtures in tests/uniffi/ are ports of the fixtures in UniFFI's own repository, with the Kotlin tests turned into common tests. Each fixture is a Rust crate and a Gradle module:

tests/uniffi/callbacks/
├── Cargo.toml            crate-type = ["cdylib", "staticlib"], or with "lib" when it is depended upon
├── build.rs              generate_scaffolding_from_current_dir() for UDL fixtures
├── build.gradle.kts      plugins { id("uniffi-tests-from-library") }
├── uniffi.toml           package_name = "callbacks"
└── src/
    ├── callbacks.udl
    ├── commonMain/rust/lib.rs
    └── commonTest/kotlin/CallbacksTest.kt

• uniffi-tests-from-library (build-logic/conventions/) applies the plugin with bindgenFromPath(<repo>/bindgen) and generateFromLibrary(), declares all targets the host can build, and adds the test dependencies (kotlin("test"), kotest assertions, coroutines-test). It sets addRuntime = false and depends on project(":runtime") instead, so tests always run against the runtime in the working tree.
• tests/build-common provides generate_scaffolding_from_current_dir(), which finds the UDL file from the directory name.
• Every fixture is a member of the Cargo workspace in the root Cargo.toml and is included in settings.gradle.kts.

Adding a fixture¶

1. Create the directory with the files above. Copy a similar fixture as a starting point.
2. Add it to members in the root Cargo.toml and include(":tests:uniffi:<name>") to settings.gradle.kts.
3. Write tests in src/commonTest/kotlin. Use jvmTest or nativeTest only for platform-specific behaviour.

Working on the generator¶

All fixtures use the bindgen from the working tree (bindgenFromPath), which is reinstalled when its sources change. A typical loop:

./gradlew :tests:uniffi:coverall:jvmTest           # fast feedback
./gradlew :tests:uniffi:coverall:macosArm64Test    # check native too

Look at the generated code in tests/uniffi/<name>/build/uniffi/bindings/. Compile errors usually point there.

Debugging crashes¶

• A test that crashes the process (SIGABRT, exit code 134) produces no console output, because the JVM dies before Gradle collects it. Read build/test-results/<task>/TEST-*.xml, or run the test class on its own with --info.
• For Rust panics, set RUST_BACKTRACE=1 in the environment of the test task.
• On JVM, -Djna.debug_load=true shows where JNA looks for the library.