LeVCS/crates/levcs-merge/tests/corpus/README.md

LeVCS conformance corpus (§8.2)

This directory is the canonical conformance fixture for the LeVCS merge engine. Any independent implementation of LeVCS that produces the same outcome on every scenario here is conformant per the spec's testing strategy: the scenarios tagged git_false_conflict = true are specifically the cases where naive Git produces a spurious conflict and LeVCS MUST resolve correctly.

Layout

Each scenario lives in its own numbered directory:

<NNN-scenario-name>/
  manifest.toml      # what to assert about the merge result
  base.<ext>         # base / common ancestor input
  ours.<ext>         # left side input
  theirs.<ext>       # right side input
  expected.<ext>     # (optional) exact expected merged output

The runner is crates/levcs-merge/tests/conformance.rs. It walks this directory, reads each manifest, runs the engine on the inputs, and asserts the outcome matches.

Manifest schema

description = "..."            # required, human-readable
path = "src/lib.rs"            # required, used for handler routing
input_ext = "rs"               # optional, defaults to extension of `path`
git_false_conflict = true      # optional, marks Git-false-conflict cases

[expected]
status   = "merged"            # "merged" | "conflict"
handler  = "tree-sitter:rust"  # required handler name
contains = ["fn a", "fn b"]    # all must appear in merged output
not_contains = []              # none may appear
content_file = "expected.rs"   # optional, exact-match against file
conflict_count = 1             # conflict-only, optional
region_descriptions_contain = ["concurrent edits"]   # conflict-only
notes_contain = ["recursive descent"]                # merged-only

A merged outcome that emits conflict markers (<<<<<<<, =======, >>>>>>>) is treated as a runner failure regardless of substring assertions — handlers are not allowed to silently smuggle conflicts through.

Adding a scenario

1. Pick the next free NNN- prefix.
2. Create the directory, drop in base/ours/theirs.<ext> files.
3. Write manifest.toml with what should hold.
4. Run cargo test -p levcs-merge --test conformance.

Scenarios should be minimal: the smallest input that exercises the behaviour. Comments inline in input files are fine — the engine treats them as ordinary content.