Add Flat encoding test coverage across all packages#7678
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Add Flat encoding test coverage across all packages#7678
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zliu41
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Mar 19, 2026
plutus-core/flat/test/Spec.hs
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| -- | Stable byte encoding tests for flat library container/composite types. | ||
| -- Wrapper types (Identity, All, Any, Dual, etc.) only have roundtrip tests | ||
| -- since their encoding stability is not critical (they are never on-chain). | ||
| testNewEncodings = testGroup "stable byte encodings" |
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We are not introducing any new encodings, so this should just be called "testEncodings"
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Renamed to testEncodingStability. Tell me if you have another idea of a better name.
| -- | Reproducible encoding generator for Flat test coverage. | ||
| -- Run: cabal run flat-encoding-generator | ||
| -- Prints expected byte sequences for all Flat test values. | ||
| executable flat-encoding-generator |
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What's the purpose of this, and in what scenario would someone want to use this executable?
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Replied by changing the code comment:
-- Golden file generator for Flat encoding stability tests.
--
-- The encoding stability tests compare encoded values against expected
-- byte sequences captured as test fixtures. This tool regenerates those
-- fixtures from source, so they don't remain opaque blobs of bits.
--
-- Example: if a bug in a Flat instance is found and the encoding must
-- change in a backward-incompatible way, the stability tests will fail.
-- Run this tool to see the new wire format, update the test fixtures,
-- and confirm the encoding change was intentional.
--
-- See: https://en.wikipedia.org/wiki/Characterization_test
-- Usage: cabal run flat-encoding-generator
plutus-core/plutus-core.cabal
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| ghc-options: | ||
| -Wno-missing-signatures -Wno-missing-deriving-strategies | ||
| -Wno-unused-packages |
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Why do you need these flags? Can you just fix the warnings?
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You're right, I just copied these from the vendored flat and flat-test stanzas without thinking. Removed them; none were actually needed here.
The vendored code itself still has a bunch of these (flat-test alone has 10). All inherited from the original upstream style. Happy to clean those up too, though that's probably a separate PR since it touches vendored code. Worth it?
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Pay down test coverage debt for Flat serialization instances. This ensures encoding stability is verified by tests before we attempt to fix the Generic derivation bug in a follow-up PR. Adds roundtrip and stable byte encoding tests for: - Flat library types (Maybe, Either, NonEmpty, Complex, Ratio, Set, Tree, Map, Seq, DList, Filler, PreAligned, and monoid/semigroup wrappers) - TPLC types (Version, Name, Kind, DeBruijn, NamedDeBruijn, SrcSpan, SrcSpans, DefaultFun, DefaultUni, and all newtype wrappers including TyName, Unique, TyDeBruijn, etc.) - PIR types (Recursivity, Strictness) - UPLC types (Binder variants, FakeNamedDeBruijn, minimal Program encoding) - Value types (K encodes as ByteString, Quantity as Integer) Also adds a standalone encoding generator executable (cabal run flat-encoding-generator) for reproducing expected byte constants.
Rename testNewEncodings to testEncodingStability for clarity. Fix plutus-core ^>=1.59 version bound to ^>=1.60. Remove unnecessary -Wno-* flags and unused text dependency from flat-encoding-generator. Improve executable comment with golden testing context and Wikipedia reference.
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Context
Approach
Added two categories of tests for Flat instances:
Stable byte encoding tests (a.k.a. golden/characterization tests) pin the exact byte representation of on-chain-critical types (Version, DeBruijn, DefaultFun, DefaultUni, Binder variants, UPLC Program, PIR Recursivity/Strictness). These detect any accidental encoding changes that would break on-chain script compatibility.
Roundtrip property tests verify
unflat (flat x) == Right xfor all Flat instances including library-internal types (monoid/semigroup wrappers, containers, etc.) where encoding stability is less critical but correctness still matters.A standalone encoding generator executable (
cabal run flat-encoding-generator) is included so anyone can reproduce the expected byte constants without GHCi sessions. It regenerates test fixtures from source so they don't remain opaque blobs of bits.BLS12_381 types are deliberately skipped (their encode/decode implementations are
error/fail).Changes
Flat library tests (
flat/test/Spec.hs)TPLC tests (
plutus-core/test/Flat/Spec.hs— new module)UPLC tests (
untyped-plutus-core/testlib/Flat/Spec.hs)(program 1.1.0 (con integer 0))test_flatinto the UPLC test entry point (was previously defined but not imported)PIR tests (
plutus-ir/test/PlutusIR/Core/Tests.hs)Value tests (
plutus-core/test/Value/Spec.hs)Infrastructure
plutus-core/tools/GenerateEncodings.hs)FOURMOLU_DISABLEtoflat/test/Spec.hs(CPP-heavy file that fourmolu cannot parse)