# `mix test.regression`
[🔗](https://github.com/riddler/statifier-ex/blob/v2.6.0/lib/mix/tasks/test.regression.ex#L1)

Runs exactly the tests listed in `test/passing_tests.json`.

Those tests passed once, so any failure here is a regression rather than a
missing feature. The conformance suites are excluded from `mix test` by
default; this task includes the tags its registry entries need.

## Usage

    mix test.regression
    mix test.regression --registry test/passing_tests.json

## Options

  * `--registry` - registry to run, defaults to `test/passing_tests.json`

Failures print ExUnit's own output, unedited. Growing the registry is
`mix test.baseline`'s job - this task never writes to it.

A registry entry that matches no file on disk fails the run. Skipping it
would silently shrink the ratchet, which is the one thing it exists to
prevent.

A passing run also prints a per-corpus coverage block: for each conformance
suite, `ratcheted/total (percent%)` against the suite's emitted corpus
files. The numerator is exactly the registry entries this run verified -
unlike `mix test.baseline`'s scan, there are no newly-passing files to add
in. A failing run prints no such block; ExUnit's own output is the whole
story then.

# `execute`

```elixir
@spec execute(argv :: [String.t()], opts :: keyword()) :: :ok | {:error, String.t()}
```

Runs the ratchet and reports the outcome instead of halting.

`opts[:runner]` replaces the `mix test` shell-out with a function of the
argument list returning an exit status, `opts[:root]` moves the corpus scan
behind the coverage block to a fixture tree. Both exist so the tests can
drive this without spawning a nested `mix test`.

# `test_env`

```elixir
@spec test_env() :: [{String.t(), String.t()}]
```

Environment for the spawned `mix test`.

The ratchet runs concurrently with `mix quality`'s own Tests stage, in the
same working directory, over largely the same modules. Scratch directories
(`Statifier.TmpDir`) are collision-proof by construction - `root/0` always
ends in a `System.pid()` segment, so the two runs cannot land on the same
path even by accident. `STATIFIER_TMP_ROOT` is set here anyway, not
for isolation but so the ratchet's pid-scoped tree lands under a
recognizable `tmp/regression/<pid>/` rather than an anonymous `tmp/<pid>/`
indistinguishable from the Tests stage's own.

---

*Consult [api-reference.md](api-reference.md) for complete listing*