test_property_merge_invariants.py
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| 1 | """Property-based tests for the three-way merge engine invariants. |
| 2 | |
| 3 | These tests use Hypothesis to generate random manifests and DAG shapes and |
| 4 | verify mathematical invariants that must hold for ANY input — not just the |
| 5 | specific inputs we thought to write as unit tests. |
| 6 | |
| 7 | Why these tests? |
| 8 | ---------------- |
| 9 | The silent-drop bug (fixed in 73427a30) survived all existing tests because |
| 10 | the existing tests only exercised SPECIFIC manifests. A property test with |
| 11 | the invariant "theirs-only files must survive merge" would have caught it |
| 12 | immediately: Hypothesis would have generated a manifest where theirs added |
| 13 | a file that ours didn't touch, run apply_merge, and found the file absent. |
| 14 | |
| 15 | Invariants tested |
| 16 | ----------------- |
| 17 | M1 Theirs-only additions survive in merged manifest. |
| 18 | M2 Ours-only additions survive in merged manifest. |
| 19 | M3 Theirs-only deletions are applied in merged manifest. |
| 20 | M4 Ours-only deletions are applied in merged manifest. |
| 21 | M5 Conflict paths are exactly the intersection of ours_changed and theirs_changed. |
| 22 | M6 Conflict paths are absent from apply_merge output (caller resolves them). |
| 23 | M7 Non-conflicting paths from both sides are correct in output. |
| 24 | M8 Identical content on both sides is never a conflict in diff_snapshots. |
| 25 | M9 apply_merge is idempotent when ours == theirs (convergence). |
| 26 | M10 merged result contains no paths from conflict_paths when they exist. |
| 27 | |
| 28 | LCA invariants |
| 29 | -------------- |
| 30 | L1 LCA(A, A) == A. |
| 31 | L2 LCA(A, B) is an ancestor of A (reachable from A). |
| 32 | L3 LCA(A, B) is an ancestor of B (reachable from B). |
| 33 | L4 LCA(A, B) == LCA(B, A) — commutativity. |
| 34 | L5 If A is ancestor of B, LCA(A, B) == A. |
| 35 | |
| 36 | Snapshot integrity invariant |
| 37 | ---------------------------- |
| 38 | SI1 Every object_id referenced in a merged manifest exists in the object store. |
| 39 | """ |
| 40 | from __future__ import annotations |
| 41 | |
| 42 | import datetime |
| 43 | import json |
| 44 | import pathlib |
| 45 | |
| 46 | import pytest |
| 47 | from hypothesis import HealthCheck, given, settings |
| 48 | from hypothesis import strategies as st |
| 49 | |
| 50 | from muse.core.merge_engine import ( |
| 51 | apply_merge, |
| 52 | detect_conflicts, |
| 53 | diff_snapshots, |
| 54 | find_merge_base, |
| 55 | ) |
| 56 | from muse.core.types import Manifest, fake_id, blob_id |
| 57 | from muse.core.paths import head_path, heads_dir, muse_dir |
| 58 | |
| 59 | |
| 60 | # --------------------------------------------------------------------------- |
| 61 | # Strategies — building blocks for random manifests and DAGs |
| 62 | # --------------------------------------------------------------------------- |
| 63 | |
| 64 | |
| 65 | def _h(label: str) -> str: |
| 66 | return fake_id(label) |
| 67 | |
| 68 | |
| 69 | # A path looks like "src/module_3.py" or "README.md". |
| 70 | _path_strategy = st.text( |
| 71 | alphabet=st.characters(whitelist_categories=("Ll", "Lu", "Nd"), whitelist_characters="/_-."), |
| 72 | min_size=1, |
| 73 | max_size=32, |
| 74 | ).filter(lambda s: "/" not in s or not s.startswith("/")) |
| 75 | |
| 76 | # A content hash is a 64-char hex string (we use sha256 of a label for uniqueness). |
| 77 | _hash_strategy = st.text( |
| 78 | alphabet="0123456789abcdef", |
| 79 | min_size=64, |
| 80 | max_size=64, |
| 81 | ) |
| 82 | |
| 83 | # A manifest is a dict of path → hash with at most 40 entries. |
| 84 | _manifest_strategy = st.dictionaries( |
| 85 | keys=_path_strategy, |
| 86 | values=_hash_strategy, |
| 87 | min_size=0, |
| 88 | max_size=40, |
| 89 | ) |
| 90 | |
| 91 | |
| 92 | # --------------------------------------------------------------------------- |
| 93 | # Helpers |
| 94 | # --------------------------------------------------------------------------- |
| 95 | |
| 96 | |
| 97 | def _linear_repo( |
| 98 | tmp_path: pathlib.Path, |
| 99 | ) -> tuple[pathlib.Path, str]: |
| 100 | """Create a minimal code-domain Muse repo for LCA tests.""" |
| 101 | from muse.core.ids import hash_commit as compute_commit_id, hash_snapshot as compute_snapshot_id |
| 102 | from muse.core.commits import ( |
| 103 | CommitRecord, |
| 104 | write_commit, |
| 105 | ) |
| 106 | from muse.core.snapshots import ( |
| 107 | SnapshotRecord, |
| 108 | write_snapshot, |
| 109 | ) |
| 110 | |
| 111 | dot_muse = muse_dir(tmp_path) |
| 112 | dot_muse.mkdir(exist_ok=True) |
| 113 | repo_id = fake_id("repo") |
| 114 | (dot_muse / "repo.json").write_text( |
| 115 | json.dumps({"repo_id": repo_id, "domain": "code", "default_branch": "main"}), |
| 116 | encoding="utf-8", |
| 117 | ) |
| 118 | (dot_muse / "refs" / "heads").mkdir(parents=True, exist_ok=True) |
| 119 | (dot_muse / "snapshots").mkdir(exist_ok=True) |
| 120 | (dot_muse / "commits").mkdir(exist_ok=True) |
| 121 | (dot_muse / "objects").mkdir(exist_ok=True) |
| 122 | return tmp_path, repo_id |
| 123 | |
| 124 | |
| 125 | def _make_commit_lca( |
| 126 | root: pathlib.Path, |
| 127 | repo_id: str, |
| 128 | manifest: Manifest, |
| 129 | message: str = "c", |
| 130 | parent_id: str | None = None, |
| 131 | parent2_id: str | None = None, |
| 132 | ) -> str: |
| 133 | from muse.core.ids import hash_commit as compute_commit_id, hash_snapshot as compute_snapshot_id |
| 134 | from muse.core.commits import ( |
| 135 | CommitRecord, |
| 136 | write_commit, |
| 137 | ) |
| 138 | from muse.core.snapshots import ( |
| 139 | SnapshotRecord, |
| 140 | write_snapshot, |
| 141 | ) |
| 142 | |
| 143 | snap_id = compute_snapshot_id(manifest) |
| 144 | committed_at = datetime.datetime.now(datetime.timezone.utc) |
| 145 | parent_ids: list[str] = [] |
| 146 | if parent_id: |
| 147 | parent_ids.append(parent_id) |
| 148 | if parent2_id: |
| 149 | parent_ids.append(parent2_id) |
| 150 | commit_id = compute_commit_id( |
| 151 | parent_ids=parent_ids, |
| 152 | snapshot_id=snap_id, |
| 153 | message=message, |
| 154 | committed_at_iso=committed_at.isoformat(), |
| 155 | ) |
| 156 | write_snapshot(root, SnapshotRecord(snapshot_id=snap_id, manifest=manifest)) |
| 157 | write_commit(root, CommitRecord( |
| 158 | commit_id=commit_id, |
| 159 | branch="main", |
| 160 | snapshot_id=snap_id, |
| 161 | message=message, |
| 162 | committed_at=committed_at, |
| 163 | parent_commit_id=parent_id, |
| 164 | parent2_commit_id=parent2_id, |
| 165 | )) |
| 166 | return commit_id |
| 167 | |
| 168 | |
| 169 | # =========================================================================== |
| 170 | # M — apply_merge / diff_snapshots / detect_conflicts invariants |
| 171 | # =========================================================================== |
| 172 | |
| 173 | |
| 174 | class TestMergeEngineInvariantsM: |
| 175 | """Property-based invariants for the pure merge functions.""" |
| 176 | |
| 177 | @given( |
| 178 | base=_manifest_strategy, |
| 179 | extra_theirs=_manifest_strategy, |
| 180 | ) |
| 181 | @settings(max_examples=200, suppress_health_check=[HealthCheck.too_slow]) |
| 182 | def test_M1_theirs_only_additions_survive( |
| 183 | self, base: Manifest, extra_theirs: Manifest |
| 184 | ) -> None: |
| 185 | """M1: every file theirs adds (not in base, not touched by ours) is in merged.""" |
| 186 | # ours: no changes from base |
| 187 | ours = dict(base) |
| 188 | # theirs: base + extra_theirs (disjoint new keys only) |
| 189 | theirs = dict(base) |
| 190 | new_keys = {k: v for k, v in extra_theirs.items() if k not in base} |
| 191 | theirs.update(new_keys) |
| 192 | |
| 193 | ours_changed = diff_snapshots(base, ours) |
| 194 | theirs_changed = diff_snapshots(base, theirs) |
| 195 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 196 | |
| 197 | merged = apply_merge(base, ours, theirs, ours_changed, theirs_changed, conflicts) |
| 198 | |
| 199 | for path, obj_id in new_keys.items(): |
| 200 | assert path in merged, ( |
| 201 | f"M1 VIOLATED: theirs-only addition '{path}' absent from merged.\n" |
| 202 | f"base keys: {set(base)}\n" |
| 203 | f"extra_theirs keys: {set(new_keys)}\n" |
| 204 | f"merged keys: {set(merged)}" |
| 205 | ) |
| 206 | assert merged[path] == obj_id, ( |
| 207 | f"M1 VIOLATED: theirs-only addition '{path}' has wrong hash in merged." |
| 208 | ) |
| 209 | |
| 210 | @given( |
| 211 | base=_manifest_strategy, |
| 212 | extra_ours=_manifest_strategy, |
| 213 | ) |
| 214 | @settings(max_examples=200, suppress_health_check=[HealthCheck.too_slow]) |
| 215 | def test_M2_ours_only_additions_survive( |
| 216 | self, base: Manifest, extra_ours: Manifest |
| 217 | ) -> None: |
| 218 | """M2: every file ours adds (not in base, not touched by theirs) is in merged.""" |
| 219 | ours = dict(base) |
| 220 | new_keys = {k: v for k, v in extra_ours.items() if k not in base} |
| 221 | ours.update(new_keys) |
| 222 | theirs = dict(base) |
| 223 | |
| 224 | ours_changed = diff_snapshots(base, ours) |
| 225 | theirs_changed = diff_snapshots(base, theirs) |
| 226 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 227 | |
| 228 | merged = apply_merge(base, ours, theirs, ours_changed, theirs_changed, conflicts) |
| 229 | |
| 230 | for path, obj_id in new_keys.items(): |
| 231 | assert path in merged, f"M2 VIOLATED: ours-only addition '{path}' absent from merged." |
| 232 | assert merged[path] == obj_id |
| 233 | |
| 234 | @given(base=_manifest_strategy, del_keys=st.frozensets(st.text(min_size=1, max_size=20))) |
| 235 | @settings(max_examples=200, suppress_health_check=[HealthCheck.too_slow]) |
| 236 | def test_M3_theirs_only_deletions_applied( |
| 237 | self, base: Manifest, del_keys: frozenset[str] |
| 238 | ) -> None: |
| 239 | """M3: files theirs deletes (and ours does not touch) are absent from merged.""" |
| 240 | to_delete = {k for k in del_keys if k in base} |
| 241 | if not to_delete: |
| 242 | return # no relevant keys to test |
| 243 | |
| 244 | ours = dict(base) |
| 245 | theirs = {k: v for k, v in base.items() if k not in to_delete} |
| 246 | |
| 247 | ours_changed = diff_snapshots(base, ours) |
| 248 | theirs_changed = diff_snapshots(base, theirs) |
| 249 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 250 | |
| 251 | merged = apply_merge(base, ours, theirs, ours_changed, theirs_changed, conflicts) |
| 252 | |
| 253 | for path in to_delete: |
| 254 | assert path not in merged, ( |
| 255 | f"M3 VIOLATED: theirs-only deletion '{path}' still present in merged." |
| 256 | ) |
| 257 | |
| 258 | @given(base=_manifest_strategy, del_keys=st.frozensets(st.text(min_size=1, max_size=20))) |
| 259 | @settings(max_examples=200, suppress_health_check=[HealthCheck.too_slow]) |
| 260 | def test_M4_ours_only_deletions_applied( |
| 261 | self, base: Manifest, del_keys: frozenset[str] |
| 262 | ) -> None: |
| 263 | """M4: files ours deletes (and theirs does not touch) are absent from merged.""" |
| 264 | to_delete = {k for k in del_keys if k in base} |
| 265 | if not to_delete: |
| 266 | return |
| 267 | |
| 268 | theirs = dict(base) |
| 269 | ours = {k: v for k, v in base.items() if k not in to_delete} |
| 270 | |
| 271 | ours_changed = diff_snapshots(base, ours) |
| 272 | theirs_changed = diff_snapshots(base, theirs) |
| 273 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 274 | |
| 275 | merged = apply_merge(base, ours, theirs, ours_changed, theirs_changed, conflicts) |
| 276 | |
| 277 | for path in to_delete: |
| 278 | assert path not in merged, ( |
| 279 | f"M4 VIOLATED: ours-only deletion '{path}' still present in merged." |
| 280 | ) |
| 281 | |
| 282 | @given(base=_manifest_strategy, ours=_manifest_strategy, theirs=_manifest_strategy) |
| 283 | @settings(max_examples=300, suppress_health_check=[HealthCheck.too_slow]) |
| 284 | def test_M5_conflicts_are_divergent_intersection( |
| 285 | self, |
| 286 | base: Manifest, |
| 287 | ours: Manifest, |
| 288 | theirs: Manifest, |
| 289 | ) -> None: |
| 290 | """M5: detect_conflicts returns exactly paths where both changed AND disagree. |
| 291 | |
| 292 | Formally: conflicts = {p ∈ ours_changed ∩ theirs_changed | ours.get(p) ≠ theirs.get(p)}. |
| 293 | |
| 294 | Convergent changes — both deleted the same file (both .get(p) == None), or |
| 295 | both added/modified to the same hash — are NOT conflicts. The old invariant |
| 296 | that conflicts == ours_changed ∩ theirs_changed was incorrect for these cases. |
| 297 | """ |
| 298 | ours_changed = diff_snapshots(base, ours) |
| 299 | theirs_changed = diff_snapshots(base, theirs) |
| 300 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 301 | |
| 302 | expected = { |
| 303 | p for p in ours_changed & theirs_changed |
| 304 | if ours.get(p) != theirs.get(p) |
| 305 | } |
| 306 | assert conflicts == expected, ( |
| 307 | f"M5 VIOLATED: conflict set {conflicts!r} != expected {expected!r}.\n" |
| 308 | f" ours_changed={ours_changed!r}\n" |
| 309 | f" theirs_changed={theirs_changed!r}" |
| 310 | ) |
| 311 | |
| 312 | @given(base=_manifest_strategy, ours=_manifest_strategy, theirs=_manifest_strategy) |
| 313 | @settings(max_examples=200, suppress_health_check=[HealthCheck.too_slow]) |
| 314 | def test_M6_conflict_paths_absent_from_apply_merge( |
| 315 | self, |
| 316 | base: Manifest, |
| 317 | ours: Manifest, |
| 318 | theirs: Manifest, |
| 319 | ) -> None: |
| 320 | """M6: apply_merge never writes conflict paths — callers resolve them.""" |
| 321 | ours_changed = diff_snapshots(base, ours) |
| 322 | theirs_changed = diff_snapshots(base, theirs) |
| 323 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 324 | |
| 325 | merged = apply_merge(base, ours, theirs, ours_changed, theirs_changed, conflicts) |
| 326 | |
| 327 | # Conflict paths must not be in merged at a value taken from ours or theirs |
| 328 | # (they stay at base or absent). The strict invariant: a conflict path |
| 329 | # must have been either absent from base (so it should be absent in merged) |
| 330 | # or present at base's value. |
| 331 | for path in conflicts: |
| 332 | if path in merged: |
| 333 | # If present, it must be at base's value (not ours or theirs override). |
| 334 | assert merged[path] == base.get(path), ( |
| 335 | f"M6 VIOLATED: conflict path '{path}' in merged at non-base value." |
| 336 | ) |
| 337 | |
| 338 | @given(base=_manifest_strategy, ours=_manifest_strategy, theirs=_manifest_strategy) |
| 339 | @settings(max_examples=200, suppress_health_check=[HealthCheck.too_slow]) |
| 340 | def test_M7_non_conflicting_paths_correct_in_output( |
| 341 | self, |
| 342 | base: Manifest, |
| 343 | ours: Manifest, |
| 344 | theirs: Manifest, |
| 345 | ) -> None: |
| 346 | """M7: non-conflicting ours-only changes are at ours value; theirs-only at theirs value.""" |
| 347 | ours_changed = diff_snapshots(base, ours) |
| 348 | theirs_changed = diff_snapshots(base, theirs) |
| 349 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 350 | merged = apply_merge(base, ours, theirs, ours_changed, theirs_changed, conflicts) |
| 351 | |
| 352 | for path in ours_changed - conflicts: |
| 353 | if path in ours: |
| 354 | assert merged.get(path) == ours[path], ( |
| 355 | f"M7 VIOLATED: ours-only change '{path}' not at ours value in merged." |
| 356 | ) |
| 357 | else: |
| 358 | assert path not in merged, ( |
| 359 | f"M7 VIOLATED: ours-only deletion '{path}' still present in merged." |
| 360 | ) |
| 361 | |
| 362 | for path in theirs_changed - conflicts: |
| 363 | if path in theirs: |
| 364 | assert merged.get(path) == theirs[path], ( |
| 365 | f"M7 VIOLATED: theirs-only change '{path}' not at theirs value in merged." |
| 366 | ) |
| 367 | else: |
| 368 | assert path not in merged, ( |
| 369 | f"M7 VIOLATED: theirs-only deletion '{path}' still present in merged." |
| 370 | ) |
| 371 | |
| 372 | @given(base=_manifest_strategy, common_changes=_manifest_strategy) |
| 373 | @settings(max_examples=200, suppress_health_check=[HealthCheck.too_slow]) |
| 374 | def test_M8_convergent_modify_auto_resolves( |
| 375 | self, base: Manifest, common_changes: Manifest |
| 376 | ) -> None: |
| 377 | """M8: when both branches independently arrive at the same hash, no conflict fires |
| 378 | and the merged manifest contains the path at the agreed hash. |
| 379 | |
| 380 | This is the canonical convergent-change invariant: identical outcomes are not |
| 381 | conflicts regardless of whether both sides changed the path. |
| 382 | """ |
| 383 | shared_hash = _h("shared-content") |
| 384 | path = "shared.py" |
| 385 | base_with = dict(base) |
| 386 | base_with[path] = _h("original") |
| 387 | ours = dict(base_with) |
| 388 | ours[path] = shared_hash |
| 389 | theirs = dict(base_with) |
| 390 | theirs[path] = shared_hash |
| 391 | |
| 392 | ours_changed = diff_snapshots(base_with, ours) |
| 393 | theirs_changed = diff_snapshots(base_with, theirs) |
| 394 | |
| 395 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 396 | merged = apply_merge(base_with, ours, theirs, ours_changed, theirs_changed, conflicts) |
| 397 | |
| 398 | # Convergent change: detect_conflicts must NOT flag 'path'. |
| 399 | assert path not in conflicts, ( |
| 400 | f"M8 VIOLATED: convergent path '{path}' (same hash on both sides) " |
| 401 | f"wrongly reported as conflict." |
| 402 | ) |
| 403 | # apply_merge must include 'path' at the agreed hash. |
| 404 | assert merged.get(path) == shared_hash, ( |
| 405 | f"M8 VIOLATED: merged['{path}'] = {merged.get(path)!r}, " |
| 406 | f"expected {shared_hash!r}." |
| 407 | ) |
| 408 | |
| 409 | @given(base=_manifest_strategy, changes=_manifest_strategy) |
| 410 | @settings(max_examples=200, suppress_health_check=[HealthCheck.too_slow]) |
| 411 | def test_M9_merge_ours_equals_theirs_is_convergent( |
| 412 | self, base: Manifest, changes: Manifest |
| 413 | ) -> None: |
| 414 | """M9: when ours == theirs, apply_merge produces ours exactly (no-conflict convergence).""" |
| 415 | ours = dict(changes) |
| 416 | theirs = dict(changes) |
| 417 | |
| 418 | ours_changed = diff_snapshots(base, ours) |
| 419 | theirs_changed = diff_snapshots(base, theirs) |
| 420 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 421 | |
| 422 | merged = apply_merge(base, ours, theirs, ours_changed, theirs_changed, conflicts) |
| 423 | |
| 424 | # Every non-conflicting path must be at ours (== theirs) value. |
| 425 | for path in set(ours) | set(theirs): |
| 426 | if path in conflicts: |
| 427 | continue |
| 428 | expected = ours.get(path) |
| 429 | if expected is not None: |
| 430 | assert merged.get(path) == expected, ( |
| 431 | f"M9 VIOLATED: ours == theirs but merged[{path!r}] != ours[{path!r}]." |
| 432 | ) |
| 433 | |
| 434 | @given(base=_manifest_strategy, ours=_manifest_strategy, theirs=_manifest_strategy) |
| 435 | @settings(max_examples=200, suppress_health_check=[HealthCheck.too_slow]) |
| 436 | def test_M10_untouched_base_paths_preserved( |
| 437 | self, base: Manifest, ours: Manifest, theirs: Manifest |
| 438 | ) -> None: |
| 439 | """M10: files neither branch touched remain in merged at base value.""" |
| 440 | ours_changed = diff_snapshots(base, ours) |
| 441 | theirs_changed = diff_snapshots(base, theirs) |
| 442 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 443 | merged = apply_merge(base, ours, theirs, ours_changed, theirs_changed, conflicts) |
| 444 | |
| 445 | untouched = set(base) - ours_changed - theirs_changed |
| 446 | for path in untouched: |
| 447 | assert merged.get(path) == base[path], ( |
| 448 | f"M10 VIOLATED: untouched path '{path}' changed value in merged." |
| 449 | ) |
| 450 | |
| 451 | |
| 452 | # =========================================================================== |
| 453 | # L — LCA / find_merge_base invariants |
| 454 | # =========================================================================== |
| 455 | |
| 456 | |
| 457 | class TestLCAInvariantsL: |
| 458 | """Property-based invariants for find_merge_base (Lowest Common Ancestor).""" |
| 459 | |
| 460 | @pytest.fixture |
| 461 | def repo(self, tmp_path: pathlib.Path) -> tuple[pathlib.Path, str]: |
| 462 | return _linear_repo(tmp_path) |
| 463 | |
| 464 | def test_L1_lca_of_same_commit_is_itself( |
| 465 | self, tmp_path: pathlib.Path |
| 466 | ) -> None: |
| 467 | """L1: LCA(X, X) == X for any commit X.""" |
| 468 | root, repo_id = _linear_repo(tmp_path) |
| 469 | c = _make_commit_lca(root, repo_id, {}, "root") |
| 470 | lca = find_merge_base(root, c, c) |
| 471 | assert lca == c, f"L1: LCA({c[:8]}, {c[:8]}) should be {c[:8]}, got {lca}" |
| 472 | |
| 473 | def test_L2_L3_lca_is_ancestor_of_both(self, tmp_path: pathlib.Path) -> None: |
| 474 | """L2+L3: LCA(A,B) must be in the ancestry of both A and B.""" |
| 475 | root, repo_id = _linear_repo(tmp_path) |
| 476 | c0 = _make_commit_lca(root, repo_id, {}, "base") |
| 477 | c1 = _make_commit_lca(root, repo_id, {"a.py": _h("a1")}, "ours", parent_id=c0) |
| 478 | c2 = _make_commit_lca(root, repo_id, {"b.py": _h("b1")}, "theirs", parent_id=c0) |
| 479 | |
| 480 | lca = find_merge_base(root, c1, c2) |
| 481 | assert lca is not None, "LCA of two commits with common ancestor must exist" |
| 482 | |
| 483 | from muse.core.commits import read_commit |
| 484 | |
| 485 | def _ancestors(start: str) -> set[str]: |
| 486 | visited: set[str] = set() |
| 487 | q = [start] |
| 488 | while q: |
| 489 | cid = q.pop() |
| 490 | if cid in visited: |
| 491 | continue |
| 492 | visited.add(cid) |
| 493 | commit = read_commit(root, cid) |
| 494 | if commit is None: |
| 495 | continue |
| 496 | if commit.parent_commit_id: |
| 497 | q.append(commit.parent_commit_id) |
| 498 | if commit.parent2_commit_id: |
| 499 | q.append(commit.parent2_commit_id) |
| 500 | return visited |
| 501 | |
| 502 | assert lca in _ancestors(c1), f"L2: LCA {lca[:8]} not in ancestry of A {c1[:8]}" |
| 503 | assert lca in _ancestors(c2), f"L3: LCA {lca[:8]} not in ancestry of B {c2[:8]}" |
| 504 | |
| 505 | def test_L4_lca_commutativity(self, tmp_path: pathlib.Path) -> None: |
| 506 | """L4: LCA(A, B) == LCA(B, A).""" |
| 507 | root, repo_id = _linear_repo(tmp_path) |
| 508 | c0 = _make_commit_lca(root, repo_id, {}, "base") |
| 509 | c1 = _make_commit_lca(root, repo_id, {"a.py": _h("a1")}, "c1", parent_id=c0) |
| 510 | c2 = _make_commit_lca(root, repo_id, {"b.py": _h("b1")}, "c2", parent_id=c0) |
| 511 | |
| 512 | lca_ab = find_merge_base(root, c1, c2) |
| 513 | lca_ba = find_merge_base(root, c2, c1) |
| 514 | assert lca_ab == lca_ba, ( |
| 515 | f"L4: LCA({c1[:8]}, {c2[:8]}) = {lca_ab}, " |
| 516 | f"LCA({c2[:8]}, {c1[:8]}) = {lca_ba} — not commutative" |
| 517 | ) |
| 518 | |
| 519 | def test_L5_if_a_is_ancestor_of_b_lca_is_a(self, tmp_path: pathlib.Path) -> None: |
| 520 | """L5: if A is ancestor of B, LCA(A, B) == A.""" |
| 521 | root, repo_id = _linear_repo(tmp_path) |
| 522 | c0 = _make_commit_lca(root, repo_id, {}, "base") |
| 523 | c1 = _make_commit_lca(root, repo_id, {"a.py": _h("a1")}, "c1", parent_id=c0) |
| 524 | c2 = _make_commit_lca(root, repo_id, {"b.py": _h("b1")}, "c2", parent_id=c1) |
| 525 | |
| 526 | lca = find_merge_base(root, c0, c2) |
| 527 | assert lca == c0, f"L5: c0 is ancestor of c2 so LCA should be c0, got {lca}" |
| 528 | |
| 529 | lca2 = find_merge_base(root, c1, c2) |
| 530 | assert lca2 == c1, f"L5: c1 is ancestor of c2 so LCA should be c1, got {lca2}" |
| 531 | |
| 532 | def test_L6_lca_for_merge_commit_topology(self, tmp_path: pathlib.Path) -> None: |
| 533 | """L6: diamond topology — LCA of the two branches is the fork point, not deeper.""" |
| 534 | root, repo_id = _linear_repo(tmp_path) |
| 535 | base = _make_commit_lca(root, repo_id, {}, "base") |
| 536 | a = _make_commit_lca(root, repo_id, {"a.py": _h("a")}, "a", parent_id=base) |
| 537 | b = _make_commit_lca(root, repo_id, {"b.py": _h("b")}, "b", parent_id=base) |
| 538 | # Merge commit of a and b |
| 539 | m = _make_commit_lca( |
| 540 | root, repo_id, {"a.py": _h("a"), "b.py": _h("b")}, "merge", |
| 541 | parent_id=a, parent2_id=b |
| 542 | ) |
| 543 | |
| 544 | # LCA of a and m should be a (m is a descendant of a). |
| 545 | assert find_merge_base(root, a, m) == a, "L6a" |
| 546 | # LCA of b and m should be b. |
| 547 | assert find_merge_base(root, b, m) == b, "L6b" |
| 548 | # LCA of base and m should be base. |
| 549 | assert find_merge_base(root, base, m) == base, "L6c" |
| 550 | |
| 551 | |
| 552 | # =========================================================================== |
| 553 | # SI — Snapshot integrity invariants |
| 554 | # =========================================================================== |
| 555 | |
| 556 | |
| 557 | class TestSnapshotIntegritySI: |
| 558 | """After every merge, every object_id in the snapshot must be in the store.""" |
| 559 | |
| 560 | def _object_exists(self, root: pathlib.Path, obj_id: str) -> bool: |
| 561 | """Return True if obj_id is readable from the object store.""" |
| 562 | from muse.core.object_store import read_object |
| 563 | return read_object(root, obj_id) is not None |
| 564 | |
| 565 | def test_SI1_fast_forward_snapshot_objects_all_present( |
| 566 | self, tmp_path: pathlib.Path |
| 567 | ) -> None: |
| 568 | """SI1: after fast-forward, every object in the new snapshot is in the store.""" |
| 569 | from muse.core.object_store import write_object |
| 570 | from muse.core.commits import read_commit |
| 571 | from muse.core.snapshots import read_snapshot |
| 572 | |
| 573 | root, repo_id = _linear_repo(tmp_path) |
| 574 | (head_path(root)).write_text("ref: refs/heads/main", encoding="utf-8") |
| 575 | |
| 576 | # Write real objects to the store. |
| 577 | contents = {f"file_{i}.py": f"x = {i}\n".encode() for i in range(10)} |
| 578 | manifest: Manifest = {} |
| 579 | for path, data in contents.items(): |
| 580 | obj_id = blob_id(data) |
| 581 | write_object(root, obj_id, data) |
| 582 | manifest[path] = obj_id |
| 583 | |
| 584 | base_c = _make_commit_lca(root, repo_id, {}, "base") |
| 585 | # Write feat branch with the manifest. |
| 586 | (heads_dir(root) / "main").write_text(base_c, encoding="utf-8") |
| 587 | feat_c = _make_commit_lca(root, repo_id, manifest, "feat", parent_id=base_c) |
| 588 | (heads_dir(root) / "feat").write_text(feat_c, encoding="utf-8") |
| 589 | |
| 590 | # Run merge (fast-forward). |
| 591 | from tests.cli_test_helper import CliRunner |
| 592 | runner = CliRunner() |
| 593 | env = {"MUSE_REPO_ROOT": str(root)} |
| 594 | runner.invoke(None, ["merge", "--force", "feat"], env=env, catch_exceptions=False) |
| 595 | |
| 596 | # Verify every object in main's snapshot is in the store. |
| 597 | main_head = (heads_dir(root) / "main").read_text().strip() |
| 598 | commit = read_commit(root, main_head) |
| 599 | assert commit is not None |
| 600 | snap = read_snapshot(root, commit.snapshot_id) |
| 601 | assert snap is not None |
| 602 | |
| 603 | for path, obj_id in snap.manifest.items(): |
| 604 | assert self._object_exists(root, obj_id), ( |
| 605 | f"SI1 VIOLATED: blob {obj_id[:8]} for '{path}' missing from store " |
| 606 | f"after fast-forward merge." |
| 607 | ) |
| 608 | |
| 609 | def test_SI2_apply_merge_output_all_hashes_from_inputs( |
| 610 | self, tmp_path: pathlib.Path |
| 611 | ) -> None: |
| 612 | """SI2: every hash in apply_merge output came from base, ours, or theirs. |
| 613 | |
| 614 | This ensures apply_merge never invents a hash. Any invented hash would |
| 615 | reference a non-existent object and corrupt the repo on checkout. |
| 616 | """ |
| 617 | base = {"a.py": _h("a-base"), "b.py": _h("b-base"), "c.py": _h("c-base")} |
| 618 | ours = {"a.py": _h("a-ours"), "b.py": _h("b-base"), "d.py": _h("d-ours")} |
| 619 | theirs = {"a.py": _h("a-theirs"), "c.py": _h("c-theirs"), "e.py": _h("e-theirs")} |
| 620 | |
| 621 | all_known_hashes = ( |
| 622 | set(base.values()) | set(ours.values()) | set(theirs.values()) |
| 623 | ) |
| 624 | |
| 625 | ours_changed = diff_snapshots(base, ours) |
| 626 | theirs_changed = diff_snapshots(base, theirs) |
| 627 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 628 | merged = apply_merge(base, ours, theirs, ours_changed, theirs_changed, conflicts) |
| 629 | |
| 630 | for path, obj_id in merged.items(): |
| 631 | assert obj_id in all_known_hashes, ( |
| 632 | f"SI2 VIOLATED: apply_merge produced unknown hash {obj_id[:8]} for '{path}'. " |
| 633 | f"Invented hashes corrupt the object store." |
| 634 | ) |
| 635 | |
| 636 | @given(base=_manifest_strategy, ours=_manifest_strategy, theirs=_manifest_strategy) |
| 637 | @settings(max_examples=300, suppress_health_check=[HealthCheck.too_slow]) |
| 638 | def test_SI3_all_merged_hashes_come_from_known_inputs( |
| 639 | self, base: Manifest, ours: Manifest, theirs: Manifest |
| 640 | ) -> None: |
| 641 | """SI3: property version of SI2 — apply_merge never generates new hashes.""" |
| 642 | all_known = set(base.values()) | set(ours.values()) | set(theirs.values()) |
| 643 | |
| 644 | ours_changed = diff_snapshots(base, ours) |
| 645 | theirs_changed = diff_snapshots(base, theirs) |
| 646 | conflicts = detect_conflicts(ours_changed, theirs_changed, ours, theirs) |
| 647 | merged = apply_merge(base, ours, theirs, ours_changed, theirs_changed, conflicts) |
| 648 | |
| 649 | for path, obj_id in merged.items(): |
| 650 | assert obj_id in all_known, ( |
| 651 | f"SI3 VIOLATED: merged[{path!r}] = {obj_id[:8]} was not in any input manifest." |
| 652 | ) |
| 653 | |
| 654 | |
| 655 | # =========================================================================== |
| 656 | # DT — Determinism tests |
| 657 | # =========================================================================== |
| 658 | |
| 659 | |
| 660 | class TestDeterminismDT: |
| 661 | """Snapshot IDs and commit IDs must be deterministic across calls and dict orderings.""" |
| 662 | |
| 663 | def test_DT1_snapshot_id_independent_of_dict_insertion_order(self) -> None: |
| 664 | """DT1: compute_snapshot_id produces the same ID regardless of dict key order.""" |
| 665 | from muse.core.ids import hash_snapshot as compute_snapshot_id |
| 666 | |
| 667 | manifest = {f"file_{i:03d}.py": _h(f"content-{i}") for i in range(50)} |
| 668 | |
| 669 | # Build the same dict in reverse insertion order. |
| 670 | manifest_reversed: Manifest = {} |
| 671 | for k in reversed(list(manifest.keys())): |
| 672 | manifest_reversed[k] = manifest[k] |
| 673 | |
| 674 | id_forward = compute_snapshot_id(manifest) |
| 675 | id_reversed = compute_snapshot_id(manifest_reversed) |
| 676 | assert id_forward == id_reversed, ( |
| 677 | "DT1 VIOLATED: compute_snapshot_id is sensitive to dict insertion order. " |
| 678 | "Two repos with the same content would get different snapshot IDs." |
| 679 | ) |
| 680 | |
| 681 | def test_DT2_snapshot_id_is_stable_across_calls(self) -> None: |
| 682 | """DT2: the same manifest always produces the same snapshot_id.""" |
| 683 | from muse.core.ids import hash_snapshot as compute_snapshot_id |
| 684 | |
| 685 | manifest = {"app.py": _h("app"), "README.md": _h("readme")} |
| 686 | ids = {compute_snapshot_id(manifest) for _ in range(100)} |
| 687 | assert len(ids) == 1, "DT2 VIOLATED: compute_snapshot_id is not deterministic." |
| 688 | |
| 689 | def test_DT3_empty_manifest_has_stable_id(self) -> None: |
| 690 | """DT3: the empty manifest always has the same snapshot_id.""" |
| 691 | from muse.core.ids import hash_snapshot as compute_snapshot_id |
| 692 | ids = {compute_snapshot_id({}) for _ in range(50)} |
| 693 | assert len(ids) == 1, "DT3: empty manifest snapshot_id is not stable." |
| 694 | |
| 695 | def test_DT4_commit_id_stable_for_same_inputs(self) -> None: |
| 696 | """DT4: compute_commit_id with the same inputs always returns the same ID.""" |
| 697 | from muse.core.ids import hash_commit as compute_commit_id |
| 698 | kwargs = dict( |
| 699 | parent_ids=["abc" * 21 + "a"], |
| 700 | snapshot_id=_h("snap"), |
| 701 | message="test commit", |
| 702 | committed_at_iso="2026-01-01T00:00:00+00:00", |
| 703 | ) |
| 704 | ids = {compute_commit_id(**kwargs) for _ in range(50)} |
| 705 | assert len(ids) == 1, "DT4: compute_commit_id is not deterministic." |
| 706 | |
| 707 | @given(manifest=_manifest_strategy) |
| 708 | @settings(max_examples=200) |
| 709 | def test_DT5_snapshot_id_property_stable(self, manifest: Manifest) -> None: |
| 710 | """DT5: for any random manifest, snapshot_id is the same when called twice.""" |
| 711 | from muse.core.ids import hash_snapshot as compute_snapshot_id |
| 712 | assert compute_snapshot_id(manifest) == compute_snapshot_id(manifest) |
| 713 | |
| 714 | @given(manifest=_manifest_strategy) |
| 715 | @settings(max_examples=200) |
| 716 | def test_DT6_snapshot_id_order_independent_property(self, manifest: Manifest) -> None: |
| 717 | """DT6: for any manifest, shuffling key insertion order doesn't change the ID.""" |
| 718 | from muse.core.ids import hash_snapshot as compute_snapshot_id |
| 719 | keys = list(manifest.keys()) |
| 720 | # Build a copy with reversed key order |
| 721 | shuffled = {k: manifest[k] for k in reversed(keys)} |
| 722 | assert compute_snapshot_id(manifest) == compute_snapshot_id(shuffled), ( |
| 723 | "DT6 VIOLATED: snapshot_id changed when dict key order changed." |
| 724 | ) |