Node sets a test's concurrency to Infinity for `true` whenever the test
has a parent, and to os.availableParallelism() - 1 only for the root
test. Every test and suite a program declares has a parent, so `true`
now runs all of its subtests at once instead of capping them at the CPU
count minus one.
The concurrency fixture adds a suite of 64 concurrent tests that checks
all of them run at once.
node:test changes, matching Node 24.22:
- { concurrency } on describe, suite, test, it and t.test sets how many
subtests run at once: a number, true for os.availableParallelism() - 1,
or false for 1. Subtests inherit the parent's value.
- Above 1, each subtest runs on its own fiber. Subtests start in
declaration order as slots free up, and t.test and test() calls inside a
concurrent test start the subtest at once; t.test's promise settles when
it finishes. The parent finishes after all of them.
- Results, diagnostics and failures are reported in declaration order.
- A concurrent subtest waits after its beforeEach hooks, and a concurrent
suite before its children, for as many turns as Node's runner does, so
sibling bodies interleave as they do there.
- A concurrency that is not an integer from 1 to 4294967295 throws Node's
ERR_OUT_OF_RANGE RangeError when the test or suite is created.
- Nested test() calls and hooks inside a concurrent subtest attach to the
subtest that runs on the calling fiber.
The concurrency fixture compares the reporter output, the order of the
bodies' side effects, and the range errors with Node, plain and with
SCRIPTC_SAN=1.
node:test's mock.fn(original[, implementation]) and t.mock.fn compile.
A Mock<F> is the function-with-properties record { %call, mock }: the
callable is a wrapper closure that shares the mock context with the mock
field. The context records each call's arguments, result, error and this,
and keeps the current implementation, the original and the one-time
implementations by call index. fn.mock supports, as in Node 24.22:
- calls, read as a copy of the log;
- callCount();
- mockImplementation(fn);
- mockImplementationOnce(fn[, onCall]), for the next call by default, a
later registration for the same index replacing the earlier one;
- resetCalls();
- restore(), which brings back the original.
A throwing implementation records the error and rethrows it. Functions
with fixed parameters or a single rest array parameter are supported; a
union return type needs an undefined arm. mock.fn() without an original,
mock.method, the tracker's reset and restoreAll, and t.mock.method are
refused with SC2020.
The node:test fixture mock-fn compares the behavior with Node, and
tests/diagnostics/mock-fences.ts covers the refusals.
node:test changes, matching Node 24.22:
- t.before, t.after, t.beforeEach and t.afterEach lower. t.before runs
when it is called; a throw fails the test and the subtests that follow,
which skip their body and beforeEach hooks and run their afterEach hooks.
t.beforeEach and t.afterEach wrap every descendant subtest. t.after runs
after the test's afterEach chain, also when the body throws, and a throw
fails the test.
- t.plan(count) counts the test's t.assert calls and subtests. A mismatch
fails the test with Node's "plan expected N assertions but received M"
string, unless an assertion failed first.
- t.fullName joins the names from the outermost suite or test with " > ".
- Tests and suites under a todo suite or test are todo, with a bare TODO
directive, unless they are skipped or carry their own todo message. A
todo suite reports its directive.
- describe.only, suite.only and { only: true } on a suite mark it. At each
level, when a child is marked or contains a marked test or suite, only
those children run.
- The failing-tests section lists failures in completion order, so
subtests come before the test that ran them, and prints thrown strings
quoted, as Node inspects them.
The fixtures ctx-hooks, ctx-plan, todo-suites, suite-variants,
only-nested and thrown-values compare the reporter output and exit code
with Node.
- The ratified rename rider (world-unification §7 lane 5): "DOM" collided with the browser DOM and, post-lane-1, the structure is no longer a document tree. Comments and doc prose now say "the checked-dynamic tree" for the noun and "dyn" adjectivally; runtime symbol names (scr_dyn_*), the error.domClone libCall, and the real web DOMException family are unchanged.
- The few user-facing strings carrying the nickname move with it (the structuredClone cyclic message, the dc subscriber/publish fences, two emitter ICE texts); diagnostics snapshots regenerated (96 pass). One private compiler constant (DOM_PROTO_METHOD_NAMES -> DYN_PROTO_METHOD_NAMES) rides along.
- Mechanical sweep, 142 files, comments/prose only — no behavior change.
Chris Tate