Luna Flow
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consistency tutorial

This page shows maintainers how to run the cross-package consistency tests and how to add a new law when a change touches more than one numeric package.

Quick start

Run the suite from a workspace that contains the module (the repository wrapper keeps the build directory clean):

sh tools/run_moon_clean_exec.sh test -p Luna-Flow/floating/consistency --target native

A passing run ends with passed: N, failed: 0. The suite is also part of just pr.

Everyday tasks

Run one test

sh tools/run_moon_clean_exec.sh test -p Luna-Flow/floating/consistency \
  --filter "decimal quantize*"

Add a cross-package law

Write a white-box test in core_wbtest.mbt (arithmetic laws) or api_audit_wbtest.mbt (observable API behaviour). State the law against an exact oracle whenever possible:

///|
test "bin_float addition of small dyadics is exact" {
  let a = @bin_float.BinFloat::from_int(3)
  let b = @bin_float.BinFloat::from_int(5)
  let sum = @semantic.SemanticScalar::from_bin_float(a + b)
  let exact = @semantic.SemanticScalar::from_bin_float(
    @bin_float.BinFloat::from_int(8),
  )
  assert_true(sum == exact)
}

Use official decTest rows as fixed witnesses when you test GDA cohort or flag rules, and quote the row id in the test name.

Decide where a test belongs

A law about one package goes into that package’s own tests. A test belongs here when it needs two or more packages, or internal helpers from outside their package, or an oracle such as semantic exact rationals.

Going further

  • The conformance corpora (verification) check each core against external references; this suite checks the cores against each other and against exact arithmetic.
  • internal tutorial shows the helpers several tests exercise.

Common pitfalls

  • Run from a workspace. The package imports sibling Luna-Flow modules; use the repository wrapper or a workspace that resolves them.
  • Keep tests deterministic. Use fixed seeds and explicit contexts; no test may depend on timing or the target’s Double formatting.

Next steps