refactor(test): hoist duplicated test helpers into ailang-test-support

closes #60

The fixture-corpus filter (NON_PARSEABLE_FIXTURES + list_ail_fixtures)
was copy-pasted across three test crates and drifted out of sync as
new reject fixtures landed; the examples_dir / workspace_root path
walk was reimplemented ~30 more times across the suite, under two
spellings (workspace_root / ws_root).

Introduce crates/ailang-test-support — a zero-dependency, dev-only
leaf crate — as the single home for these helpers:
- NON_PARSEABLE_FIXTURES, list_ail_fixtures
- workspace_root, examples_dir
- canonical_workspace_root (symlink-resolved variant, for the tsan/
  race tests that feed the root into native build steps)

All integration-test copies across ailang-core, ailang-surface,
ailang-prose, ailang-check, and ail now import from the shared crate;
the local definitions and their now-orphaned path imports are removed.
Path helpers resolve via the support crate's own CARGO_MANIFEST_DIR,
so they return the correct absolute paths from any caller.

ail_bin helpers are intentionally left in place: they depend on
env!("CARGO_BIN_EXE_ail"), which Cargo only defines when compiling the
ail crate's own integration tests, so they cannot move to a shared
crate.

Behaviour-identical: same paths, same fixture lists; full workspace
test suite green. Net -177 LOC.

Cargo.lock

@@ -11,6 +11,7 @@ dependencies = [
  "ailang-core",
  "ailang-prose",
  "ailang-surface",
+ "ailang-test-support",
  "anyhow",
  "blake3",
  "clap",
@@ -25,6 +26,7 @@ dependencies = [
  "ailang-core",
  "ailang-mir",
  "ailang-surface",
+ "ailang-test-support",
  "indexmap",
  "serde",
  "serde_json",
@@ -48,6 +50,7 @@ name = "ailang-core"
 version = "0.0.1"
 dependencies = [
  "ailang-surface",
+ "ailang-test-support",
  "blake3",
  "indexmap",
  "serde",
@@ -73,6 +76,7 @@ version = "0.0.1"
 dependencies = [
  "ailang-core",
  "ailang-surface",
+ "ailang-test-support",
 ]
 
 [[package]]
@@ -81,11 +85,16 @@ version = "0.0.1"
 dependencies = [
  "ailang-core",
  "ailang-kernel",
+ "ailang-test-support",
  "serde_json",
  "tempfile",
  "thiserror",
 ]
 
+[[package]]
+name = "ailang-test-support"
+version = "0.0.1"
+
 [[package]]
 name = "anstream"
 version = "1.0.0"

Cargo.toml

@@ -8,6 +8,7 @@ members = [
     "crates/ailang-kernel",
     "crates/ailang-surface",
     "crates/ailang-prose",
+    "crates/ailang-test-support",
     "crates/ail",
 ]
 # `ail-embed/` is intentionally NOT a member: it depends on the
@@ -39,6 +40,7 @@ ailang-codegen = { path = "crates/ailang-codegen" }
 ailang-kernel = { path = "crates/ailang-kernel" }
 ailang-surface = { path = "crates/ailang-surface" }
 ailang-prose = { path = "crates/ailang-prose" }
+ailang-test-support = { path = "crates/ailang-test-support" }
 
 [profile.release]
 lto = "thin"

crates/ail/Cargo.toml

@@ -21,3 +21,4 @@ anyhow.workspace = true
 [dev-dependencies]
 tempfile.workspace = true
 blake3.workspace = true
+ailang-test-support.workspace = true

crates/ail/tests/ct1_check_cli.rs

@@ -11,6 +11,7 @@
 //! someone reverts the migration (or breaks the canonical-form
 //! acceptance path in the registry), that test goes red.
 
+use ailang_test_support::examples_dir;
 use std::path::PathBuf;
 use std::process::Command;
 
@@ -19,15 +20,6 @@ fn ail_bin() -> PathBuf {
     PathBuf::from(env!("CARGO_BIN_EXE_ail"))
 }
 
-fn examples_dir() -> PathBuf {
-    // CARGO_MANIFEST_DIR points at `crates/ail`; examples/ sits at the
-    // workspace root, two levels up.
-    PathBuf::from(env!("CARGO_MANIFEST_DIR"))
-        .join("..")
-        .join("..")
-        .join("examples")
-}
-
 /// Property: a workspace whose entry module contains a bare
 /// cross-module Type::Con / Term::Ctor reference — here `Mystery_Type`,
 /// a name no module in the workspace declares (post-prep.1: in-scope

crates/ail/tests/e2e.rs

@@ -3,6 +3,7 @@
 //! This test guards the most important property of the entire pipeline:
 //! AST → typecheck → LLVM IR → clang → binary → correct stdout.
 
+use ailang_test_support::workspace_root;
 use std::path::Path;
 use std::process::Command;
 
@@ -2801,15 +2802,6 @@ fn merge_prose_prints_framed_prompt() {
 
 // ---------- ext-cli.1: CLI accepts `.ail` (Form A) source files ----------
 
-fn workspace_root() -> std::path::PathBuf {
-    Path::new(env!("CARGO_MANIFEST_DIR"))
-        .parent()
-        .unwrap()
-        .parent()
-        .unwrap()
-        .to_path_buf()
-}
-
 /// Property: `ail check` accepts a Form-A `.ail` source file (not just
 /// the Form-B `.ail.json` canonical form) and exits zero on a
 /// well-formed program. Guards against the post-rename misleading-JSON

crates/ail/tests/embed_e2e.rs

@@ -4,18 +4,16 @@
 //! + `libailang_rt.a`, run it, assert the `s == 25` assertion holds
 //! (exit 0). This is the whole-milestone existence proof.
 
+use ailang_test_support::workspace_root;
 use std::path::PathBuf;
 use std::process::Command;
 
 fn ail_bin() -> &'static str { env!("CARGO_BIN_EXE_ail") }
 fn manifest() -> PathBuf { PathBuf::from(env!("CARGO_MANIFEST_DIR")) }
-fn ws_root() -> PathBuf {
-    manifest().parent().unwrap().parent().unwrap().to_path_buf()
-}
 
 #[test]
 fn c_host_calls_exported_scalar_kernel() {
-    let fixture = ws_root().join("examples").join("embed_backtest_step.ail");
+    let fixture = workspace_root().join("examples").join("embed_backtest_step.ail");
     let host_c = manifest().join("tests").join("embed").join("host.c");
     let outdir = std::env::temp_dir()
         .join(format!("ail-embed-e2e-{}", std::process::id()));

crates/ail/tests/embed_missing_main_baseline.rs

@@ -9,18 +9,13 @@
 //!
 //! Pure reader: writes nothing to the repo.
 
-use std::path::{Path, PathBuf};
+use ailang_test_support::workspace_root;
 use std::process::Command;
 
 fn ail_bin() -> &'static str {
     env!("CARGO_BIN_EXE_ail")
 }
 
-fn workspace_root() -> PathBuf {
-    let manifest_dir = env!("CARGO_MANIFEST_DIR");
-    Path::new(manifest_dir).parent().unwrap().parent().unwrap().to_path_buf()
-}
-
 #[test]
 fn ail_build_on_main_free_module_is_rejected_at_cli() {
     let fixture = workspace_root()

crates/ail/tests/embed_rc_accounting_tsan.rs

@@ -4,11 +4,7 @@
 //! Per-thread-ctx build: tsan-clean + exit 0. RED until rc.c gains
 //! ailang_ctx_* + __ail_tls_ctx (link error: undefined symbols).
 use std::process::Command;
-use std::path::PathBuf;
 
-fn ws_root() -> PathBuf {
-    PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../..").canonicalize().unwrap()
-}
 
 fn cc(args: &[&str], ctx: &str) {
     let st = Command::new("clang").args(args).status().expect("spawn clang");
@@ -17,7 +13,7 @@ fn cc(args: &[&str], ctx: &str) {
 
 #[test]
 fn rc_accounting_per_ctx_is_tsan_clean() {
-    let root = ws_root();
+    let root = ailang_test_support::canonical_workspace_root();
     let tmp = std::env::temp_dir().join("ail_m2_rcacct");
     std::fs::create_dir_all(&tmp).unwrap();
     let rc_o = tmp.join("rc.o");
@@ -48,7 +44,7 @@ fn rc_accounting_shared_ctx_is_flagged_by_tsan() {
     // calling ailang_rc_alloc/ailang_rc_dec → concurrent
     // ctx->alloc_count++ is a genuine data race tsan MUST report.
     // Proves the de-globalisation property is not vacuous.
-    let root = ws_root();
+    let root = ailang_test_support::canonical_workspace_root();
     let tmp = std::env::temp_dir().join("ail_m2_rcacct_neg");
     std::fs::create_dir_all(&tmp).unwrap();
     let rc_o = tmp.join("rc.o");

crates/ail/tests/embed_rc_global_stats_race.rs

@@ -28,12 +28,8 @@
 //! build of any kernel emits `libailang_rt.a`; the C host links the
 //! runtime archive directly and never calls a kernel.
 
-use std::path::PathBuf;
 use std::process::Command;
 
-fn ws_root() -> PathBuf {
-    PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../..").canonicalize().unwrap()
-}
 fn ail_bin() -> &'static str { env!("CARGO_BIN_EXE_ail") }
 
 /// 8 threads * 2_000_000 cycles — must match the `#define`s in
@@ -47,7 +43,7 @@ fn global_rc_stats_counters_are_exact_under_thread_contention() {
     let outdir = std::env::temp_dir().join(format!(
         "ail-rc-global-stats-race-{}", std::process::id()));
     std::fs::create_dir_all(&outdir).unwrap();
-    let root = ws_root();
+    let root = ailang_test_support::canonical_workspace_root();
 
     // Any kernel staticlib build emits libailang_rt.a alongside it.
     let st = Command::new(ail_bin())

crates/ail/tests/embed_record_e2e.rs

@@ -23,14 +23,12 @@
 //! `e2e.rs::build_and_run_with_rc_stats` (the runtime's fixed
 //! `ailang_rc_stats: allocs=N frees=M live=K` shape).
 
+use ailang_test_support::workspace_root;
 use std::path::PathBuf;
 use std::process::Command;
 
 fn ail_bin() -> &'static str { env!("CARGO_BIN_EXE_ail") }
 fn manifest() -> PathBuf { PathBuf::from(env!("CARGO_MANIFEST_DIR")) }
-fn ws_root() -> PathBuf {
-    manifest().parent().unwrap().parent().unwrap().to_path_buf()
-}
 
 #[derive(Debug)]
 struct RcStats {
@@ -44,7 +42,7 @@ struct RcStats {
 /// `AILANG_RC_STATS=1`, and return the `ailang_ctx_free` readback.
 fn build_link_run_embed(fixture: &str, host_rel: &str, extra_cc: &[&str]) -> RcStats {
     let module = fixture.strip_suffix(".ail").expect("fixture is a .ail file");
-    let fixture_path = ws_root().join("examples").join(fixture);
+    let fixture_path = workspace_root().join("examples").join(fixture);
     let host_c = manifest().join("tests").join(host_rel);
     let outdir = std::env::temp_dir().join(format!(
         "ail-embed-record-e2e-{}-{}",

crates/ail/tests/embed_staticlib_cli.rs

@@ -2,18 +2,14 @@
 //! produces `lib<entry>.a` (program-only) + a separate
 //! `libailang_rt.a`, and emits NO executable / NO `@main`.
 
-use std::path::{Path, PathBuf};
+use ailang_test_support::workspace_root;
 use std::process::Command;
 
 fn ail_bin() -> &'static str { env!("CARGO_BIN_EXE_ail") }
-fn ws_root() -> PathBuf {
-    Path::new(env!("CARGO_MANIFEST_DIR"))
-        .parent().unwrap().parent().unwrap().to_path_buf()
-}
 
 #[test]
 fn staticlib_emit_produces_two_archives() {
-    let fixture = ws_root().join("examples").join("embed_backtest_step.ail");
+    let fixture = workspace_root().join("examples").join("embed_backtest_step.ail");
     let outdir = std::env::temp_dir()
         .join(format!("ail-embed-cli-{}", std::process::id()));
     std::fs::create_dir_all(&outdir).unwrap();
@@ -39,7 +35,7 @@ fn staticlib_emit_produces_two_archives() {
 #[test]
 fn staticlib_emit_requires_an_export() {
     // embed_noentry_baseline has no `(export …)` fn.
-    let fixture = ws_root().join("examples")
+    let fixture = workspace_root().join("examples")
         .join("embed_noentry_baseline.ail");
     let outdir = std::env::temp_dir()
         .join(format!("ail-embed-noexp-{}", std::process::id()));

crates/ail/tests/embed_swarm_tsan.rs

@@ -6,9 +6,6 @@
 use std::process::Command;
 use std::path::PathBuf;
 
-fn ws_root() -> PathBuf {
-    PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../..").canonicalize().unwrap()
-}
 fn ail_bin() -> &'static str { env!("CARGO_BIN_EXE_ail") }
 
 fn build_staticlib(outdir: &PathBuf) {
@@ -16,7 +13,7 @@ fn build_staticlib(outdir: &PathBuf) {
     let st = Command::new(ail_bin())
         .args(["build", "examples/embed_backtest_step.ail",
                "--emit=staticlib", "--alloc=rc", "-o", outdir.to_str().unwrap()])
-        .current_dir(ws_root()).status().expect("ail build");
+        .current_dir(ailang_test_support::canonical_workspace_root()).status().expect("ail build");
     assert!(st.success(), "ail build --emit=staticlib failed");
 }
 
@@ -24,7 +21,7 @@ fn build_staticlib(outdir: &PathBuf) {
 fn scalar_swarm_per_ctx_is_tsan_clean_and_matches_oracle() {
     let outdir = std::env::temp_dir().join("ail_m2_swarm_ok");
     build_staticlib(&outdir);
-    let root = ws_root();
+    let root = ailang_test_support::canonical_workspace_root();
     let bin = outdir.join("swarm_ok");
     let st = Command::new("clang").args([
         "-O1", "-g", "-fsanitize=thread", "-pthread",

crates/ail/tests/embed_tick_e2e.rs

@@ -28,14 +28,12 @@
 //! `g_rc_*`, not ctx; the invariant is GLOBAL Σallocs == Σfrees
 //! across *all* stat lines, not per-ctx-line balance).
 
+use ailang_test_support::workspace_root;
 use std::path::PathBuf;
 use std::process::Command;
 
 fn ail_bin() -> &'static str { env!("CARGO_BIN_EXE_ail") }
 fn manifest() -> PathBuf { PathBuf::from(env!("CARGO_MANIFEST_DIR")) }
-fn ws_root() -> PathBuf {
-    manifest().parent().unwrap().parent().unwrap().to_path_buf()
-}
 
 #[derive(Debug)]
 struct RcStats {
@@ -49,7 +47,7 @@ struct RcStats {
 /// `AILANG_RC_STATS=1`, and return the summed RC-stats readback.
 fn build_link_run_embed(fixture: &str, host_rel: &str, extra_cc: &[&str]) -> RcStats {
     let module = fixture.strip_suffix(".ail").expect("fixture is a .ail file");
-    let fixture_path = ws_root().join("examples").join(fixture);
+    let fixture_path = workspace_root().join("examples").join(fixture);
     let host_c = manifest().join("tests").join(host_rel);
     let outdir = std::env::temp_dir().join(format!(
         "ail-embed-tick-e2e-{}-{}",

crates/ail/tests/emit_ir_staticlib_cli.rs

@@ -4,18 +4,14 @@
 //! executable-path `MissingEntryMain` rejection — the Decision-5
 //! IR-readability affordance for the artefact M1 introduced.
 
-use std::path::{Path, PathBuf};
+use ailang_test_support::workspace_root;
 use std::process::Command;
 
 fn ail_bin() -> &'static str { env!("CARGO_BIN_EXE_ail") }
-fn ws_root() -> PathBuf {
-    Path::new(env!("CARGO_MANIFEST_DIR"))
-        .parent().unwrap().parent().unwrap().to_path_buf()
-}
 
 #[test]
 fn emit_ir_staticlib_prints_kernel_forwarder_no_main() {
-    let fixture = ws_root().join("examples").join("embed_backtest_step.ail");
+    let fixture = workspace_root().join("examples").join("embed_backtest_step.ail");
     let out = Command::new(ail_bin())
         .args(["emit-ir", fixture.to_str().unwrap(), "--emit=staticlib"])
         .output().expect("ail emit-ir --emit=staticlib");
@@ -37,7 +33,7 @@ fn emit_ir_staticlib_prints_kernel_forwarder_no_main() {
 fn emit_ir_staticlib_requires_an_export() {
     // embed_noentry_baseline has no `(export …)` fn — symmetric with
     // build's zero-export guard (embed_staticlib_cli.rs).
-    let fixture = ws_root().join("examples").join("embed_noentry_baseline.ail");
+    let fixture = workspace_root().join("examples").join("embed_noentry_baseline.ail");
     let out = Command::new(ail_bin())
         .args(["emit-ir", fixture.to_str().unwrap(), "--emit=staticlib"])
         .output().expect("ail emit-ir --emit=staticlib");
@@ -54,7 +50,7 @@ fn emit_ir_default_exe_still_requires_main() {
     // Regression: --emit defaults to "exe"; emit-ir on a main-free
     // module WITHOUT --emit=staticlib must still hit MissingEntryMain
     // (the new staticlib branch must not alter the default path).
-    let fixture = ws_root().join("examples").join("embed_backtest_step.ail");
+    let fixture = workspace_root().join("examples").join("embed_backtest_step.ail");
     let out = Command::new(ail_bin())
         .args(["emit-ir", fixture.to_str().unwrap()])
         .output().expect("ail emit-ir");

crates/ail/tests/floats_e2e.rs

@@ -9,16 +9,9 @@
 //! `float_to_str`, libc `%g` plus the runtime `.0`-fallback for
 //! whole-valued Float results, per Gitea #7).
 
-use std::path::PathBuf;
+use ailang_test_support::workspace_root;
 use std::process::Command;
 
-fn workspace_root() -> PathBuf {
-    PathBuf::from(env!("CARGO_MANIFEST_DIR"))
-        .parent().unwrap()
-        .parent().unwrap()
-        .to_path_buf()
-}
-
 #[test]
 fn floats_example_prints_expected_stdout() {
     let root = workspace_root();

crates/ail/tests/ir_snapshot.rs

@@ -2,6 +2,7 @@
 //! changes to the LLVM IR. Snapshots in tests/snapshots/. Update with
 //! UPDATE_SNAPSHOTS=1 cargo test ir_snapshot_.
 
+use ailang_test_support::examples_dir;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 
@@ -44,15 +45,6 @@ fn snapshots_dir() -> PathBuf {
     Path::new(manifest_dir).join("tests").join("snapshots")
 }
 
-fn examples_dir() -> PathBuf {
-    let manifest_dir = env!("CARGO_MANIFEST_DIR");
-    Path::new(manifest_dir)
-        .parent()
-        .unwrap()
-        .parent()
-        .unwrap()
-        .join("examples")
-}
 
 fn first_diff_line(a: &str, b: &str) -> Option<(usize, String, String)> {
     let mut la = a.lines();

crates/ail/tests/mono_xmod_ctor_pattern.rs

@@ -28,14 +28,7 @@
 //! `workspace_has_typeclasses` gate so every workspace exercises the
 //! mono pass.
 
-use std::path::PathBuf;
-
-fn examples_dir() -> PathBuf {
-    let mut d = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
-    d.pop();
-    d.pop();
-    d.join("examples")
-}
+use ailang_test_support::examples_dir;
 
 /// Property: `monomorphise_workspace` must succeed on a workspace that
 /// (a) flips the typeclass gate (any `Def::Class` + `Def::Instance` is

crates/ail/tests/mq3_multi_class_e2e.rs

@@ -17,6 +17,7 @@
 //! diagnostic stream's `code` field. Stdout / runtime behaviour is
 //! out of scope here — the dispatch path is a check-time concern.
 
+use ailang_test_support::examples_dir;
 use std::path::PathBuf;
 use std::process::Command;
 
@@ -24,13 +25,6 @@ fn ail_bin() -> PathBuf {
     PathBuf::from(env!("CARGO_BIN_EXE_ail"))
 }
 
-fn examples_dir() -> PathBuf {
-    PathBuf::from(env!("CARGO_MANIFEST_DIR"))
-        .join("..")
-        .join("..")
-        .join("examples")
-}
-
 fn run_ail_check_json(entry: &str) -> std::process::Output {
     Command::new(ail_bin())
         .args(["check", "--json", examples_dir().join(entry).to_str().unwrap()])

crates/ail/tests/roundtrip_cli.rs

@@ -20,58 +20,13 @@
 //! were the only consumers of `.ail.json` walks and are retired
 //! alongside.
 
-use std::path::{Path, PathBuf};
+use ailang_test_support::{examples_dir, list_ail_fixtures};
 use std::process::Command;
 
 fn ail_bin() -> &'static str {
     env!("CARGO_BIN_EXE_ail")
 }
 
-fn workspace_root() -> PathBuf {
-    let manifest_dir = env!("CARGO_MANIFEST_DIR");
-    Path::new(manifest_dir).parent().unwrap().parent().unwrap().to_path_buf()
-}
-
-fn examples_dir() -> PathBuf {
-    workspace_root().join("examples")
-}
-
-/// Fixtures that intentionally do NOT parse — the `#55` cutover
-/// reject corpus. These are negative fixtures whose whole point is
-/// that the parser rejects them, so `parse∘render∘parse` is not a
-/// meaningful property for them and the harness must skip them.
-///
-/// Scope is deliberately minimal: only fixtures that fail at the
-/// PARSE stage belong here. The other `*reject*.ail` cutover
-/// fixtures (`borrow_return_reject`, `borrow_value_reject`,
-/// `own_return_provenance_reject`, the `embed_export_*_rejected`
-/// set, …) parse cleanly and are rejected only later at CHECK time,
-/// so they round-trip fine and are NOT excluded.
-///
-/// - `bare_slot_reject.ail`: a bare fn-type slot with no mode. The
-///   binary-ParamMode parser rejects it ("fn-type slot requires a
-///   mode: write (own T) or (borrow T)").
-const NON_PARSEABLE_FIXTURES: &[&str] = &["bare_slot_reject.ail"];
-
-fn list_ail_fixtures() -> Vec<PathBuf> {
-    let dir = examples_dir();
-    let mut paths: Vec<PathBuf> = std::fs::read_dir(&dir)
-        .unwrap_or_else(|e| panic!("read_dir({}): {e}", dir.display()))
-        .filter_map(|entry| entry.ok())
-        .map(|e| e.path())
-        .filter(|p| {
-            p.file_name()
-                .and_then(|n| n.to_str())
-                .map(|n| {
-                    n.ends_with(".ail") && !NON_PARSEABLE_FIXTURES.contains(&n)
-                })
-                .unwrap_or(false)
-        })
-        .collect();
-    paths.sort();
-    paths
-}
-
 /// CLI-pipeline idempotency (post-form-a-default-authoring §C3): for
 /// every `.ail` fixture, the user-facing pipeline
 /// `ail parse <ail> | ail render | ail parse` is byte-identical

crates/ail/tests/typeclass_22b2.rs

@@ -6,17 +6,7 @@
 //! Tasks 9 (`missing-constraint`) and 10 (`no-instance`).
 
 use ailang_core::ast::Type;
-use std::path::{Path, PathBuf};
-
-fn examples_dir() -> PathBuf {
-    let manifest_dir = env!("CARGO_MANIFEST_DIR");
-    Path::new(manifest_dir)
-        .parent()
-        .unwrap()
-        .parent()
-        .unwrap()
-        .join("examples")
-}
+use ailang_test_support::examples_dir;
 
 /// Property protected: a class method declared in a `Def::Class` must be
 /// reachable as a name in the module's `ModuleGlobals` so that pass-2

crates/ail/tests/typeclass_22b3.rs

@@ -6,16 +6,9 @@
 //! the fixtures live in `<repo>/examples/`.
 
 use ailang_core::ast::Type;
+use ailang_test_support::examples_dir;
 use std::path::PathBuf;
 
-fn examples_dir() -> PathBuf {
-    // crates/ail/ → repo root → examples/
-    let mut d = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
-    d.pop();
-    d.pop();
-    d.join("examples")
-}
-
 #[test]
 fn monomorphise_workspace_is_identity_on_class_free_workspace() {
     // Pick any class-free fixture; `examples/hello.ail.json` is

crates/ailang-check/Cargo.toml

@@ -12,3 +12,6 @@ thiserror.workspace = true
 indexmap.workspace = true
 serde.workspace = true
 serde_json.workspace = true
+
+[dev-dependencies]
+ailang-test-support.workspace = true

crates/ailang-check/tests/embed_export_gate.rs

@@ -3,13 +3,7 @@
 //! `Int`/`Float`, or whose effect set is non-empty, MUST fail
 //! `ail check` with the new diagnostic. A scalar+pure export passes.
 
-use std::path::PathBuf;
-
-fn examples_dir() -> PathBuf {
-    PathBuf::from(env!("CARGO_MANIFEST_DIR"))
-        .parent().unwrap().parent().unwrap()
-        .join("examples")
-}
+use ailang_test_support::examples_dir;
 
 fn check_codes(file: &str) -> Vec<String> {
     let path = examples_dir().join(file);

crates/ailang-check/tests/env_construction_pin.rs

@@ -12,16 +12,8 @@
 use ailang_check::{build_check_env, build_module_globals, Env};
 use ailang_core::ast::Def;
 use ailang_surface::load_workspace;
+use ailang_test_support::examples_dir;
 use std::collections::BTreeMap;
-use std::path::Path;
-
-fn examples_dir() -> std::path::PathBuf {
-    let manifest = env!("CARGO_MANIFEST_DIR");
-    Path::new(manifest)
-        .parent().expect("CARGO_MANIFEST_DIR has a parent (crates/ailang-check)")
-        .parent().expect("CARGO_MANIFEST_DIR has a grandparent (crates/)")
-        .join("examples")
-}
 
 /// Independent reproduction of every workspace-flat env seeding
 /// step. Pre-refactor, workspace-flat seeding was split between

crates/ailang-check/tests/loop_recur_typecheck_pin.rs

@@ -6,15 +6,7 @@
 
 use ailang_check::check_workspace;
 use ailang_surface::load_workspace;
-use std::path::PathBuf;
-
-fn examples_dir() -> PathBuf {
-    let manifest = env!("CARGO_MANIFEST_DIR");
-    PathBuf::from(manifest)
-        .parent().expect("CARGO_MANIFEST_DIR has a parent (crates/ailang-check)")
-        .parent().expect("CARGO_MANIFEST_DIR has a grandparent (crates/)")
-        .join("examples")
-}
+use ailang_test_support::examples_dir;
 
 /// Load the named fixture under `examples/`, run check_workspace, and
 /// return the diagnostic code list (one entry per Diagnostic).

crates/ailang-check/tests/lower_to_mir_ty.rs

@@ -8,16 +8,7 @@
 use ailang_check::elaborate_workspace;
 use ailang_mir::{Callee, MTerm, MirWorkspace, Mode, StrRep};
 use ailang_surface::load_workspace;
-use std::path::{Path, PathBuf};
-
-/// `<repo>/examples` — resolved from this crate's manifest dir,
-/// cwd-independent (same pattern as `method_collision_pin.rs`).
-fn examples_dir() -> PathBuf {
-    Path::new(env!("CARGO_MANIFEST_DIR"))
-        .parent().expect("crates/ailang-check has parent crates/")
-        .parent().expect("crates/ has parent repo root")
-        .join("examples")
-}
+use ailang_test_support::examples_dir;
 
 /// Load a witness fixture (prelude injected) and elaborate it to MIR.
 fn elaborate_fixture(module: &str) -> MirWorkspace {

crates/ailang-check/tests/method_collision_pin.rs

@@ -14,15 +14,7 @@
 
 use ailang_check::build_check_env;
 use ailang_surface::load_workspace;
-use std::path::Path;
-
-fn examples_dir() -> std::path::PathBuf {
-    let manifest = env!("CARGO_MANIFEST_DIR");
-    Path::new(manifest)
-        .parent().expect("CARGO_MANIFEST_DIR has a parent (crates/ailang-check)")
-        .parent().expect("CARGO_MANIFEST_DIR has a grandparent (crates/)")
-        .join("examples")
-}
+use ailang_test_support::examples_dir;
 
 /// Class-class repurpose: the fixture
 /// `examples/test_22b2_method_name_collision_class_class.ail.json`

crates/ailang-check/tests/workspace.rs

@@ -6,7 +6,7 @@
 
 use ailang_check::{check_workspace, Severity};
 use ailang_surface::load_workspace;
-use std::path::Path;
+use ailang_test_support::examples_dir;
 
 /// assert that the linearity check's `suggested_rewrites`
 /// payload is non-empty AND each `replacement` parses as a form-A AILang
@@ -30,10 +30,6 @@ fn assert_suggested_rewrites_well_formed(d: &ailang_check::Diagnostic) {
     }
 }
 
-fn examples_dir() -> std::path::PathBuf {
-    let manifest = env!("CARGO_MANIFEST_DIR");
-    Path::new(manifest).parent().unwrap().parent().unwrap().join("examples")
-}
 
 #[test]
 fn happy_path_resolves_qualified_import() {

crates/ailang-core/Cargo.toml

@@ -14,3 +14,4 @@ indexmap.workspace = true
 [dev-dependencies]
 tempfile.workspace = true
 ailang-surface = { path = "../ailang-surface" }
+ailang-test-support.workspace = true

crates/ailang-core/tests/carve_out_inventory.rs

@@ -20,6 +20,7 @@
 //!   for the lambda-capture-of-loop-binder rejection
 //!   (loop-binder-captured-by-lambda).
 
+use ailang_test_support::examples_dir;
 use std::collections::BTreeSet;
 
 const EXPECTED: &[&str] = &[
@@ -40,11 +41,6 @@ const EXPECTED: &[&str] = &[
     "test_recur_type_mismatch.ail.json",
 ];
 
-fn examples_dir() -> std::path::PathBuf {
-    let crate_dir = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"));
-    crate_dir.parent().unwrap().parent().unwrap().join("examples")
-}
-
 #[test]
 fn examples_ail_json_inventory_matches_carve_outs() {
     let expected: BTreeSet<&str> = EXPECTED.iter().copied().collect();

crates/ailang-core/tests/ctt2_registry_rekey.rs

@@ -15,15 +15,7 @@
 use ailang_core::canonical;
 use ailang_core::ast::Type;
 use ailang_surface::load_workspace;
-use std::path::Path;
-
-fn examples_dir() -> std::path::PathBuf {
-    let manifest = env!("CARGO_MANIFEST_DIR");
-    Path::new(manifest)
-        .parent().expect("CARGO_MANIFEST_DIR has a parent (crates/)")
-        .parent().expect("crates has a parent (workspace root)")
-        .join("examples")
-}
+use ailang_test_support::examples_dir;
 
 #[test]
 fn two_modules_with_same_bare_foo_both_register() {

crates/ailang-core/tests/hash_pin.rs

@@ -18,11 +18,7 @@
 use ailang_core::ast::*;
 use ailang_core::canonical;
 use ailang_core::hash::def_hash;
-
-fn examples_dir() -> std::path::PathBuf {
-    let manifest_dir = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"));
-    manifest_dir.parent().unwrap().parent().unwrap().join("examples")
-}
+use ailang_test_support::examples_dir;
 
 fn sample_fn() -> Def {
     Def::Fn(FnDef {

crates/ailang-core/tests/schema_coverage.rs

@@ -19,7 +19,8 @@
 //! a separate iteration); the test must not be relaxed.
 
 use std::collections::HashSet;
-use std::path::PathBuf;
+
+use ailang_test_support::{examples_dir, list_ail_fixtures};
 
 use ailang_core::ast::{
     Def, InstanceMethod, Literal, Module, NewArg, ParamMode, Pattern, Term, Type,
@@ -354,39 +355,6 @@ fn visit_module(m: &Module, observed: &mut HashSet<VariantTag>) {
     }
 }
 
-fn examples_dir() -> PathBuf {
-    let crate_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
-    crate_dir.parent().unwrap().parent().unwrap().join("examples")
-}
-
-/// Fixtures that intentionally do NOT parse — the `#55` cutover
-/// reject corpus. Negative fixtures whose whole point is that the
-/// parser rejects them, so they have no AST to scan for variant
-/// coverage and the scan must skip them. Mirrors the same list in
-/// `crates/ail/tests/roundtrip_cli.rs`.
-///
-/// - `bare_slot_reject.ail`: a bare fn-type slot with no mode. The
-///   binary-ParamMode parser rejects it ("fn-type slot requires a
-///   mode: write (own T) or (borrow T)").
-const NON_PARSEABLE_FIXTURES: &[&str] = &["bare_slot_reject.ail"];
-
-fn list_ail_fixtures() -> Vec<PathBuf> {
-    let dir = examples_dir();
-    let mut paths: Vec<PathBuf> = std::fs::read_dir(&dir)
-        .unwrap_or_else(|e| panic!("read_dir({}): {e}", dir.display()))
-        .filter_map(|entry| entry.ok())
-        .map(|e| e.path())
-        .filter(|p| {
-            p.file_name()
-                .and_then(|n| n.to_str())
-                .map(|n| n.ends_with(".ail") && !NON_PARSEABLE_FIXTURES.contains(&n))
-                .unwrap_or(false)
-        })
-        .collect();
-    paths.sort();
-    paths
-}
-
 #[test]
 fn every_ast_variant_is_observed_in_the_fixture_corpus() {
     let fixtures = list_ail_fixtures();

crates/ailang-core/tests/workspace_pin.rs

@@ -19,6 +19,7 @@
 
 use ailang_core::workspace::{Registry, RegistryEntry, WorkspaceLoadError};
 use ailang_surface::load_workspace;
+use ailang_test_support::examples_dir;
 use std::path::{Path, PathBuf};
 
 // Adapter so this integration crate can call `load_modules_with` with
@@ -37,10 +38,6 @@ fn load_one_adapter(path: &Path) -> Result<ailang_core::ast::Module, WorkspaceLo
     }
 }
 
-fn examples_dir() -> PathBuf {
-    let manifest_dir = env!("CARGO_MANIFEST_DIR");
-    Path::new(manifest_dir).parent().unwrap().parent().unwrap().join("examples")
-}
 
 #[test]
 fn loads_example_workspace_happy_path() {

crates/ailang-prose/Cargo.toml

@@ -9,3 +9,4 @@ ailang-core.workspace = true
 
 [dev-dependencies]
 ailang-surface = { path = "../ailang-surface" }
+ailang-test-support.workspace = true

crates/ailang-prose/tests/snapshot.rs

@@ -12,16 +12,7 @@
 //! purpose — Iter 20a is the seeding round, and we want every change
 //! after this to be visible in a diff.
 
-use std::path::PathBuf;
-
-fn examples_dir() -> PathBuf {
-    // tests/ runs with CARGO_MANIFEST_DIR == crates/ailang-prose.
-    let mut p = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
-    p.pop();
-    p.pop();
-    p.push("examples");
-    p
-}
+use ailang_test_support::examples_dir;
 
 fn check_snapshot(stem: &str) {
     let dir = examples_dir();

crates/ailang-surface/Cargo.toml

@@ -12,3 +12,4 @@ thiserror.workspace = true
 
 [dev-dependencies]
 tempfile.workspace = true
+ailang-test-support.workspace = true

crates/ailang-surface/tests/round_trip.rs

@@ -32,14 +32,7 @@
 //! `every_ail_fixture_matches_its_json_counterpart` (no longer
 //! expressible: only one form is hand-authored post-iter).
 
-use std::path::PathBuf;
-
-fn examples_dir() -> PathBuf {
-    // `CARGO_MANIFEST_DIR` is the surface crate root; examples live two
-    // levels up.
-    let crate_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
-    crate_dir.parent().unwrap().parent().unwrap().join("examples")
-}
+use ailang_test_support::{examples_dir, list_ail_fixtures};
 
 // Retired iter form-a.1 T9:
 // - `list_json_fixtures` helper (walked `.ail.json` for the two retired tests below).
@@ -51,34 +44,6 @@ fn examples_dir() -> PathBuf {
 //   only one form is hand-authored post-iter; counterparts are derived in-process
 //   via `ail parse`.
 
-/// Fixtures that intentionally do NOT parse — the `#55` cutover
-/// reject corpus. Negative fixtures whose whole point is that the
-/// parser rejects them, so the parse/round-trip properties below are
-/// not meaningful for them and the corpus scan must skip them.
-/// Mirrors the same list in `crates/ail/tests/roundtrip_cli.rs`.
-///
-/// - `bare_slot_reject.ail`: a bare fn-type slot with no mode. The
-///   binary-ParamMode parser rejects it ("fn-type slot requires a
-///   mode: write (own T) or (borrow T)").
-const NON_PARSEABLE_FIXTURES: &[&str] = &["bare_slot_reject.ail"];
-
-fn list_ail_fixtures() -> Vec<PathBuf> {
-    let dir = examples_dir();
-    let mut paths: Vec<PathBuf> = std::fs::read_dir(&dir)
-        .unwrap_or_else(|e| panic!("read_dir({}): {e}", dir.display()))
-        .filter_map(|entry| entry.ok())
-        .map(|e| e.path())
-        .filter(|p| {
-            p.file_name()
-                .and_then(|n| n.to_str())
-                .map(|n| n.ends_with(".ail") && !NON_PARSEABLE_FIXTURES.contains(&n))
-                .unwrap_or(false)
-        })
-        .collect();
-    paths.sort();
-    paths
-}
-
 /// Pins **idempotency-under-print** (property 2 of the post-form-a
 /// Roundtrip Invariant, design/contracts/0009-roundtrip-invariant.md): for every
 /// well-formed `.ail` text `t`, the composition `parse → print → parse`

crates/ailang-test-support/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "ailang-test-support"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+# Zero-dependency leaf crate. Holds test helpers shared across the
+# workspace's integration-test suites (path navigation, the fixture
+# corpus filter). Depended on only as a `dev-dependency`, never by
+# production code.
+[dependencies]

crates/ailang-test-support/src/lib.rs

@@ -0,0 +1,68 @@
+//! Shared helpers for the workspace's integration-test suites.
+//!
+//! Several crates' `tests/*.rs` files need the same handful of path
+//! computations and the same fixture-corpus filter. Before this crate
+//! they were copy-pasted per file and drifted out of sync. This crate
+//! is the single source; integration tests depend on it as a
+//! `dev-dependency` and `use ailang_test_support::*`.
+//!
+//! Path helpers resolve relative to *this* crate's `CARGO_MANIFEST_DIR`
+//! (`crates/ailang-test-support`), so they are independent of which
+//! crate's test binary calls them.
+
+use std::path::PathBuf;
+
+/// Absolute path to the workspace root (the directory containing
+/// `crates/` and `examples/`).
+pub fn workspace_root() -> PathBuf {
+    let crate_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
+    crate_dir
+        .parent()
+        .unwrap()
+        .parent()
+        .unwrap()
+        .to_path_buf()
+}
+
+/// [`workspace_root`] with symlinks resolved and the path normalized
+/// (`std::fs::canonicalize`). Used by the tsan/race tests that feed the
+/// root into native build/link steps where a symlinked checkout would
+/// otherwise leak a non-canonical path.
+pub fn canonical_workspace_root() -> PathBuf {
+    std::fs::canonicalize(workspace_root()).unwrap()
+}
+
+/// Absolute path to the `examples/` fixture directory at the workspace
+/// root.
+pub fn examples_dir() -> PathBuf {
+    workspace_root().join("examples")
+}
+
+/// Fixtures under `examples/` that intentionally do NOT parse — the
+/// `#55` cutover reject corpus. Negative fixtures whose whole point is
+/// that the parser rejects them, so they have no AST and any corpus
+/// scan must skip them.
+///
+/// - `bare_slot_reject.ail`: a bare fn-type slot with no mode. The
+///   binary-`ParamMode` parser rejects it ("fn-type slot requires a
+///   mode: write (own T) or (borrow T)").
+pub const NON_PARSEABLE_FIXTURES: &[&str] = &["bare_slot_reject.ail"];
+
+/// All parseable `.ail` fixtures under `examples/`, sorted, with the
+/// [`NON_PARSEABLE_FIXTURES`] reject corpus filtered out.
+pub fn list_ail_fixtures() -> Vec<PathBuf> {
+    let dir = examples_dir();
+    let mut paths: Vec<PathBuf> = std::fs::read_dir(&dir)
+        .unwrap_or_else(|e| panic!("read_dir({}): {e}", dir.display()))
+        .filter_map(|entry| entry.ok())
+        .map(|e| e.path())
+        .filter(|p| {
+            p.file_name()
+                .and_then(|n| n.to_str())
+                .map(|n| n.ends_with(".ail") && !NON_PARSEABLE_FIXTURES.contains(&n))
+                .unwrap_or(false)
+        })
+        .collect();
+    paths.sort();
+    paths
+}