feat(test): add --shard flag to split a test run across machines#35057
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bartlomieju wants to merge 1 commit into
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feat(test): add --shard flag to split a test run across machines#35057bartlomieju wants to merge 1 commit into
bartlomieju wants to merge 1 commit into
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`deno test --shard=<index>/<count>` runs only the test files belonging to the given 1-based shard, so a suite can be split across machines (as in Vitest, Jest, and Playwright). The discovered files are sorted for a stable order and split into <count> consecutive, balanced groups; the selection happens before any --shuffle so it is deterministic across machines.
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Large test suites are commonly split across CI machines, which Vitest, Jest,
and Playwright all support with a
--shardflag.deno testhad noequivalent, so the whole suite had to run on one machine.
This adds
deno test --shard=<index>/<count>(1-based index). The discoveredtest files are sorted for a stable order, then split into
<count>consecutive, balanced groups, and only the files for
<index>are run. Everyfile lands in exactly one shard and group sizes differ by at most one. The
selection happens before any
--shuffle, so a given shard runs the same fileson every machine regardless of the shuffle seed. Invalid values
(
index > count,indexorcountof 0, missing/) are rejected atflag-parse time.
Sharding is a pre-filter on the discovered file list, independent of how files
are executed, so it composes cleanly with filtering and any future test-runner
isolation/pooling changes.
This intentionally does not include cross-shard result merging (a combined
summary across shards); each shard reports its own subset and fails its own CI
job, and a merge step pairs naturally with the json reporter as a follow-up.