Facade and backend-swap surface

Test cases for the taktora-log facade (taktora-log facade crate (FEAT_0071)) and the backend-swap surface (Backend-swap surface (FEAT_0073)) — single-facade routing, re-exports, object safety, one-shot init, pre-existing-logger precedence, and the tracing bridge.

Test Case: Facade-only emission lands DLT bytes at the daemon TEST_0800
status: implemented
verifies: REQ_0800
links incoming: REQ_0800

Goal. Confirm that a caller using only the taktora-log facade (no direct taktora-log-dlt dependency at the call site) produces DLT bytes that arrive at a co-located daemon, exercising the single-facade contract.

Fixture. End-to-end test at crates/taktora-log-dlt/tests/via_facade.rs:22-63 — a UDS-bound UnixListener stands in for dlt-daemon; a DltBackend is built with AppId("TKEX") / CtxId("MAIN") and installed via taktora_log::init().with_sink(...).

Steps.

  1. Bind a Unix-domain socket inside a temp dir.

  2. Build a DltBackend pointed at the socket and install it via taktora_log::init().with_sink(...).start().

  3. Emit via taktora_log::info!(target: "tk.endtoend", ...) — the facade re-export, not log::info! directly.

  4. Read the bytes off the socket and parse with dlt_core::parse::dlt_message.

Expected outcome. The parsed DLT message’s application ID is "TKEX" — proving the facade routes through the active LogSink with no direct backend coupling at the call site.
Test Case: taktora-log re-exports compile as drop-in log macros TEST_0801
status: implemented
verifies: REQ_0801
links incoming: REQ_0801

Goal. Confirm that debug! / error! / info! / trace! / warn! are re-exported from taktora_log so a caller depending only on taktora-log can use them as drop-in equivalents of the upstream log::* macros.

Fixture. Compile-only test at crates/taktora-log/tests/reexports.rs:6-15.

Steps.

  1. use taktora_log::{debug, error, info, trace, warn};

  2. Invoke each macro once inside #[test].

Expected outcome. The test binary compiles. Any missing re-export is a build break, so passing compilation is the verification.
Test Case: LogSink is object-safe TEST_0802
status: implemented
verifies: REQ_0802
links incoming: REQ_0802

Goal. Pin that LogSink stays object-safe so backends remain usable as Box<dyn LogSink> / Arc<dyn LogSink> for runtime selection — the backend-swap surface depends on this.

Fixture. Compile-only test at crates/taktora-log/tests/log_sink_object_safe.rs:9-13. Adapter forwarding (LogSink → log::Log) is additionally exercised in crates/taktora-log/tests/adapter.rs:25-38.

Steps.

  1. Declare fn assert_object_safe(_: &dyn LogSink) {}.

  2. Reference the function so the compiler instantiates the &dyn LogSink coercion.

Expected outcome. Compilation succeeds. If a future change adds a generic method or a Self: Sized bound that breaks object safety, this test fails to compile.
Test Case: Second taktora_log::init() returns AlreadyInitialized TEST_0803
status: implemented
verifies: REQ_0803
links incoming: REQ_0803

Goal. Confirm the one-shot init builder selects a backend on the first call and refuses to silently override on the second — the second call must return InitError::AlreadyInitialized.

Fixture. crates/taktora-log/tests/init_oneshot.rs:13-25. The test isolates the global log::Log slot by running in its own integration-test binary.

Steps.

  1. Call init().with_sink(Arc::new(Console::stderr_default())).start() — must succeed.

  2. Call init().with_sink(...).start() a second time.

Expected outcome. The second call returns Err(InitError::AlreadyInitialized).
Test Case: Pre-installed log::Log wins over taktora_log::init() TEST_0804
status: implemented
verifies: REQ_0804
links incoming: REQ_0804

Goal. Confirm that an integrator who registers their own log::Log via log::set_logger / log::set_boxed_logger before invoking taktora_log::init() keeps it — init detects the pre-existing logger and returns InitError::PreExistingLogger rather than overriding.

Fixture. crates/taktora-log/tests/init_respects_pre_existing.rs:33-44.

Steps.

  1. Install a PreExisting logger via log::set_boxed_logger.

  2. Call init().with_sink(NeverCalled)... — the NeverCalled sink panics if hit.

  3. Emit log::info!("ping").

Expected outcome. Init returns Err(InitError::PreExistingLogger); the PreExisting logger receives "ping"; NeverCalled is never invoked.
Test Case: tracing::* events reach the active LogSink TEST_0805
status: implemented
verifies: REQ_0805
links incoming: REQ_0805

Goal. Confirm that events emitted via tracing::info! / tracing::warn! / tracing::error! flow through the tracing-log bridge and are captured by the active LogSink — so existing taktora-executor-tracing emitters keep working without rewrite.

Fixture. crates/taktora-log/tests/tracing_bridge.rs:26-43. The bridge is activated passively by the tracing/log cargo feature declared in crates/taktora-log/Cargo.toml.

Steps.

  1. Install a Capture LogSink via init().with_sink(...).with_max_level(Trace).start().

  2. Emit tracing::info!(target: "tk.bridge.test", "hello from tracing").

  3. Read the captured records vector.

Expected outcome. At least one captured record contains both "hello from tracing" and the target "tk.bridge.test".