sinter Join the waitlist

Know which CI failures are real.

Sinter ingests the test history that Temper records in CI and tells you, on every pull request, whether a failure is a known flake or a new bug.

Join the waitlist Private alpha. Free while it's rough.
Sinter 2 failures are known flaky tests, 0 new failures

Both failures match tests that also fail on main without a code change. Re-running is safe.

ImportTest · dedupes rows across partitions 23% flaky
ParserTest · parses 13F with missing CUSIP 8% flaky

How it works

  1. 1

    Add Temper to your test suite

    An ExUnit formatter that records every test outcome to a JSONL file, with the git commit it ran on. Open source, on Hex, no service required.

  2. 2

    Push the history from CI

    One step at the end of the job: mix temper.push. Sinter never runs your tests and never sees your code, only the outcomes.

  3. 3

    Open a pull request

    A test that passes and fails on the same commit is flaky. Sinter sees every run, every retry and every partition, so it can say which failures are which.

Outcomes per commit a mixed row is what flaky means
3f2a1c9
9b41e02
c07d5aa
e1d20f4
77fe2c0
5d9a04b
pass fail

Knowledge base

Public, no account needed. Why tests flake, and how to fix them, in Elixir terms.
Shared database state Passes alone, fails in a full run, fails more as the suite grows.
Async and receive timeouts assert_receive that is fine on a laptop and late on a loaded CI runner.
Order dependency A test that only passes after another one has run first.
Sandbox ownership across processes A Task or GenServer writing through a connection the sandbox does not own.

The first entries are published with the alpha.

Built in the open

Temper on Hex The recording half is a plain ExUnit formatter you can read in an afternoon. hex.pm/packages/temper
The ElixirForum thread Where the CI history story was asked for, and shaped. Temper: flaky test detection for ExUnit
The war story A week of dogfooding on a real financial-data pipeline, and what it caught. volcov.dev

In private alpha with a few Elixir teams.

Free while it is rough, built by one person, GitHub Actions first. Leave an address and you will hear back personally.

No list, no newsletter. One email when your invite is ready.