transaction: add a test-utils probe that drives 2PC one phase at a time

Cargo.toml

@@ -15,6 +15,9 @@ prometheus = ["prometheus/push", "prometheus/process"]
 # Enable integration tests with a running TiKV and PD instance.
 # Use $PD_ADDRS, comma separated, to set the addresses the tests use.
 integration-tests = []
+# Test probes: drive a transaction's two-phase commit one phase at a time
+# (`Transaction::probe`). For tests only.
+test-utils = []
 
 [lib]
 name = "tikv_client"

Makefile

@@ -5,11 +5,11 @@ export RUSTFLAGS=-Dwarnings
 export PD_ADDRS     ?= 127.0.0.1:2379
 export MULTI_REGION ?= 1
 
-ALL_FEATURES := integration-tests
+ALL_FEATURES := integration-tests test-utils
 
 NEXTEST_ARGS := --config-file $(shell pwd)/config/nextest.toml
 
-INTEGRATION_TEST_ARGS := --features "integration-tests" --test-threads 1
+INTEGRATION_TEST_ARGS := --features "integration-tests test-utils" --test-threads 1
 
 RUN_INTEGRATION_TEST := cargo nextest run ${NEXTEST_ARGS} --all ${INTEGRATION_TEST_ARGS}
 
@@ -24,7 +24,7 @@ check: generate
 	cargo clippy --all-targets --features "${ALL_FEATURES}" -- -D clippy::all
 
 unit-test: generate
-	cargo nextest run ${NEXTEST_ARGS} --all --no-default-features
+	cargo nextest run ${NEXTEST_ARGS} --all --no-default-features --features test-utils
 
 integration-test: integration-test-txn integration-test-raw
 

src/transaction/mod.rs

@@ -23,6 +23,8 @@ pub use transaction::Mutation;
 pub use transaction::Scanner;
 pub use transaction::Transaction;
 pub use transaction::TransactionOptions;
+#[cfg(feature = "test-utils")]
+pub use transaction::TransactionProbe;
 
 mod buffer;
 mod client;