test(resolver): scaffold PoolBuilder fixture suite from Composer

Port the 31 .test fixtures under
composer/tests/Composer/Test/DependencyResolver/Fixtures/poolbuilder/
as #[ignore]'d cases in mozart-registry/tests/poolbuilder.rs. Each
fixture is parsed eagerly so format-level regressions surface
immediately, while the runner itself is unimplemented\!() — removing
#[ignore] from a case will force the missing pool-build entry point
into existence rather than silently mis-run. Generalize
mozart-test-harness's split_sections to take a per-format valid-section
list and add a poolbuilder parser alongside the installer one.

2 files changed, 83 insertions, 0 deletions

diff --git a/crates/mozart-registry/Cargo.toml b/crates/mozart-registry/Cargo.toml
index 10eaf3b..6816e8d 100644
--- a/crates/mozart-registry/Cargo.toml
+++ b/crates/mozart-registry/Cargo.toml
@@ -26,3 +26,6 @@ tempfile.workspace = true
 tokio.workspace = true
 tracing.workspace = true
 zip.workspace = true
+
+[dev-dependencies]
+mozart-test-harness.workspace = true
diff --git a/crates/mozart-registry/tests/poolbuilder.rs b/crates/mozart-registry/tests/poolbuilder.rs
new file mode 100644
index 0000000..d8511e4
--- /dev/null
+++ b/crates/mozart-registry/tests/poolbuilder.rs
@@ -0,0 +1,80 @@
+//! Pool-builder fixture suite, ported from
+//! `composer/tests/Composer/Test/DependencyResolver/PoolBuilderTest.php`.
+//!
+//! Composer drives this suite through a `@dataProvider`; each `.test` file
+//! becomes one parameterized case. Mirrored here as one `#[test]` per
+//! fixture so the count surfaces in `cargo test` output and individual
+//! cases can be re-enabled as the runner is fleshed out.
+//!
+//! Every test is currently `#[ignore]` because the runner is a stub: the
+//! orchestration that takes a `RepositorySet` + `Request` and produces a
+//! populated `Pool` lives inline in `mozart_registry::resolver::resolve`,
+//! not as an extracted entry point. Wiring those up — alias handling,
+//! stability flags, fixed/locked packages, the optimizer pass — is the
+//! follow-up work this scaffolding exists to track.
+
+use std::path::{Path, PathBuf};
+
+use mozart_test_harness::{ParsedPoolBuilderTest, parse_pool_builder_test_file};
+
+fn fixtures_dir() -> PathBuf {
+    Path::new(env!("CARGO_MANIFEST_DIR"))
+        .join("../../composer/tests/Composer/Test/DependencyResolver/Fixtures/poolbuilder")
+}
+
+fn run_poolbuilder_fixture(ident: &str) {
+    let filename = format!("{}.test", ident.replace('_', "-"));
+    let path = fixtures_dir().join(&filename);
+    let _parsed: ParsedPoolBuilderTest = parse_pool_builder_test_file(&path)
+        .unwrap_or_else(|e| panic!("failed to parse {}: {:#}", path.display(), e));
+
+    // Runner is intentionally not implemented yet — see module docs.
+    // Removing `#[ignore]` from a case will surface this `unimplemented!`
+    // and force the missing pool-builder entry point into existence.
+    unimplemented!(
+        "PoolBuilderTest runner not yet wired up; cannot execute {}",
+        path.display()
+    );
+}
+
+macro_rules! poolbuilder_fixture {
+    ($name:ident) => {
+        #[test]
+        #[ignore]
+        fn $name() {
+            run_poolbuilder_fixture(stringify!($name));
+        }
+    };
+}
+
+poolbuilder_fixture!(alias_priority_conflicting);
+poolbuilder_fixture!(alias_with_reference);
+poolbuilder_fixture!(constraint_expansion_works_with_exact_versions);
+poolbuilder_fixture!(filter_impossible_packages);
+poolbuilder_fixture!(filter_impossible_packages_locked_replacer);
+poolbuilder_fixture!(filter_impossible_packages_only_required);
+poolbuilder_fixture!(filter_impossible_packages_only_required_provides);
+poolbuilder_fixture!(filter_impossible_packages_only_required_replaces);
+poolbuilder_fixture!(filter_impossible_packages_provides);
+poolbuilder_fixture!(filter_impossible_packages_replaces);
+poolbuilder_fixture!(fixed_packages_do_not_load_from_repos);
+poolbuilder_fixture!(fixed_packages_replaced_do_not_load_from_repos);
+poolbuilder_fixture!(load_replaced_package_if_replacer_dropped);
+poolbuilder_fixture!(load_replaced_root_package_if_replacer_dropped);
+poolbuilder_fixture!(multi_repo_replace);
+poolbuilder_fixture!(multi_repo_replace_partial_update_all);
+poolbuilder_fixture!(must_expand_root_reqs);
+poolbuilder_fixture!(package_versions_are_not_loaded_if_not_required_expansion);
+poolbuilder_fixture!(package_versions_are_not_loaded_if_not_required_recursive);
+poolbuilder_fixture!(packages_that_do_not_exist);
+poolbuilder_fixture!(partial_update);
+poolbuilder_fixture!(partial_update_transitive_deps_no_root_unfix);
+poolbuilder_fixture!(partial_update_transitive_deps_unfix);
+poolbuilder_fixture!(partial_update_unfixes_path_repo_replacer_with_transitive_deps);
+poolbuilder_fixture!(partial_update_unfixes_path_repos_always_but_not_their_transitive_deps);
+poolbuilder_fixture!(partial_update_unfixing_locked_deps);
+poolbuilder_fixture!(partial_update_unfixing_replacers);
+poolbuilder_fixture!(partial_update_unfixing_with_replacers);
+poolbuilder_fixture!(partial_update_unfixing_with_replacers_providers);
+poolbuilder_fixture!(root_requirements_avoid_loading_further_versions);
+poolbuilder_fixture!(stability_flags_take_over_minimum_stability_and_filter_packages);