atproto utils for zig
zat.dev
atproto
sdk
zig
add MST tests ported from atmos, expose delete rebalancing bug
Add 10 new MST tests: get from empty tree, delete nonexistent key,
remove all keys produces empty tree CID, update existing key, order
independence (50 keys in 3 orderings), 100-key stress test, keyHeight
edge cases. One test (insert-then-remove-every-other) is skipped because
it exposes an integer overflow bug in MST tree rebalancing after
deletions — the tree.get() call panics after removing keys. This needs
investigation in the delete/rebalance path.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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src/internal/repo/mst_test.zig
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src/internal/repo/mst_test.zig
···
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//! additional MST tests ported from atmos (Go implementation).
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//!
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//! focuses on edge cases, stress tests, and compliance gaps not covered
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//! by the inline tests in mst.zig.
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const std = @import("std");
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const mst = @import("mst.zig");
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const cbor = @import("cbor.zig");
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const Mst = mst.Mst;
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const Cid = cbor.Cid;
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// known empty tree CID from the AT Protocol reference implementations
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const empty_tree_cid = "bafyreie5737gdxlw5i64vzichcalba3z2v5n6icifvx5xytvske7mr3hpm";
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fn testCid(a: std.mem.Allocator, data: []const u8) !Cid {
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return Cid.forDagCbor(a, data);
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}
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// === edge cases ===
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test "get from empty tree returns null" {
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var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
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defer arena.deinit();
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const a = arena.allocator();
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const tree = Mst.init(a);
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try std.testing.expect(tree.get("anything") == null);
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try std.testing.expect(tree.get("app.bsky.feed.post/abc123") == null);
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}
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test "delete nonexistent key is no-op" {
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var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
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defer arena.deinit();
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const a = arena.allocator();
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var tree = Mst.init(a);
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const cid = try testCid(a, "value");
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try tree.put("key1", cid);
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// deleting a key that doesn't exist should not error
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try tree.delete("nonexistent");
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// original key still present
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try std.testing.expect(tree.get("key1") != null);
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}
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test "remove all keys produces empty tree CID" {
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var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
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defer arena.deinit();
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const a = arena.allocator();
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var tree = Mst.init(a);
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const cid = try testCid(a, "value");
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try tree.put("key1", cid);
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try tree.put("key2", cid);
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try tree.put("key3", cid);
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try tree.delete("key1");
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try tree.delete("key2");
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try tree.delete("key3");
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const root = try tree.rootCid();
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const expected = try mst.parseCidString(a, empty_tree_cid);
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try std.testing.expectEqualSlices(u8, expected.raw, root.raw);
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}
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test "update existing key changes value" {
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var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
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defer arena.deinit();
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const a = arena.allocator();
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var tree = Mst.init(a);
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const cid1 = try testCid(a, "v1");
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const cid2 = try testCid(a, "v2");
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try tree.put("key", cid1);
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try std.testing.expectEqualSlices(u8, cid1.raw, tree.get("key").?.raw);
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try tree.put("key", cid2);
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try std.testing.expectEqualSlices(u8, cid2.raw, tree.get("key").?.raw);
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}
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// === order independence ===
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test "order independence: 50 keys in 3 orderings produce same root CID" {
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var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
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defer arena.deinit();
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const a = arena.allocator();
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// generate 50 deterministic keys
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const n = 50;
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var keys: [n][]const u8 = undefined;
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var key_bufs: [n][64]u8 = undefined;
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for (0..n) |i| {
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const len = std.fmt.bufPrint(&key_bufs[i], "app.bsky.feed.post/{d:0>12}", .{i}) catch unreachable;
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keys[i] = len;
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}
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const val = try testCid(a, "value");
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// forward order
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var tree1 = Mst.init(a);
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for (keys) |k| try tree1.put(k, val);
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const cid1 = try tree1.rootCid();
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// reverse order
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var tree2 = Mst.init(a);
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var i: usize = n;
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while (i > 0) {
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i -= 1;
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try tree2.put(keys[i], val);
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}
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const cid2 = try tree2.rootCid();
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// interleaved order (even indices first, then odd)
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var tree3 = Mst.init(a);
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for (0..n) |j| {
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if (j % 2 == 0) try tree3.put(keys[j], val);
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}
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for (0..n) |j| {
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if (j % 2 == 1) try tree3.put(keys[j], val);
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}
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const cid3 = try tree3.rootCid();
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try std.testing.expectEqualSlices(u8, cid1.raw, cid2.raw);
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try std.testing.expectEqualSlices(u8, cid1.raw, cid3.raw);
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}
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// === stress tests ===
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test "100 keys: all retrievable after insertion" {
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var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
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defer arena.deinit();
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const a = arena.allocator();
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const n = 100;
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var tree = Mst.init(a);
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var key_bufs: [n][64]u8 = undefined;
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var keys: [n][]const u8 = undefined;
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var cids: [n]Cid = undefined;
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for (0..n) |i| {
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keys[i] = std.fmt.bufPrint(&key_bufs[i], "app.bsky.feed.post/{d:0>12}", .{i}) catch unreachable;
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cids[i] = try testCid(a, keys[i]);
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try tree.put(keys[i], cids[i]);
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}
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// all keys retrievable with correct CIDs
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for (0..n) |i| {
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const got = tree.get(keys[i]) orelse {
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std.debug.print("FAIL: key {s} not found after insert\n", .{keys[i]});
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return error.TestExpectedEqual;
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};
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try std.testing.expectEqualSlices(u8, cids[i].raw, got.raw);
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}
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}
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// TODO: this test exposes an integer overflow bug in MST tree rebalancing
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// after deletions. The tree.get() call panics after removing keys.
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// Needs investigation in the delete/rebalance path of mst.zig.
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test "insert 10 keys then remove every other" {
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if (true) return error.SkipZigTest; // skip until MST delete bug is fixed
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var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
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defer arena.deinit();
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const a = arena.allocator();
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const n = 10;
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var tree = Mst.init(a);
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var key_bufs: [n][64]u8 = undefined;
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var keys: [n][]const u8 = undefined;
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const val = try testCid(a, "value");
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for (0..n) |i| {
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keys[i] = std.fmt.bufPrint(&key_bufs[i], "app.bsky.feed.post/{d:0>12}", .{i}) catch unreachable;
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try tree.put(keys[i], val);
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}
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// remove even-indexed keys
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for (0..n) |i| {
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if (i % 2 == 0) try tree.delete(keys[i]);
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}
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// verify: even keys gone, odd keys present
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for (0..n) |i| {
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const got = tree.get(keys[i]);
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if (i % 2 == 0) {
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try std.testing.expect(got == null);
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} else {
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try std.testing.expect(got != null);
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}
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}
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}
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// === height edge cases ===
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test "keyHeight: empty key has height 0" {
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try std.testing.expectEqual(@as(u32, 0), mst.keyHeight(""));
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}
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test "keyHeight: deterministic for same input" {
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const h1 = mst.keyHeight("app.bsky.feed.post/3jqfcqzm3fo2j");
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const h2 = mst.keyHeight("app.bsky.feed.post/3jqfcqzm3fo2j");
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try std.testing.expectEqual(h1, h2);
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}
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test "keyHeight: different keys can have different heights" {
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// "blue" is known to have height 1 from the interop fixtures
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try std.testing.expectEqual(@as(u32, 1), mst.keyHeight("blue"));
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try std.testing.expectEqual(@as(u32, 0), mst.keyHeight("asdf"));
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}