Tests

cargo test

Suite

• The specification vectors in tests/vectors_data, generated from the spec's vectors.json.
• Long fills, scalar draws and random access against the stream dumps in tests/data.
• The spec's conformance cases in tests/conformance, and every item of its checklist.
• Feature tests: --features rand, rayon, serde, simd-intrinsics and wgpu. The wgpu test skips without an adapter.

tests/vectors.rs checks every vector of the specification. tests/streams.rs compares long fills, scalar draws and random access against reference stream dumps in tests/data, complex fills included.

tests/conformance.rs reads the six conformance files of the spec: scalar and filled bounded integers, f64 and f32 normals, exponentials, weighted choices, and the hashes of long outputs. Every fill case checks its values, its end position, its scalar draws, and the fill cut at elements 1, 7, 20, 21 and n − 1 and continued on one generator. An f32 normal fill is cut at 2, 8, 20 and the largest even element below n, since a cut inside a pair drops a sin half. The tests then show each checklist item:

• Fallback by global draw index: the rejected bounded elements and the ziggurat misses, and a start one draw later that shifts the output by one element.
• Width: the bounded draws name their width, so range 1000 gives CROSS_BELOW32[3] as u32 and CROSS_BELOW64[3] as u64. Range 0 returns 0 after one draw.
• n = 0: the seven empty cases. An empty f64 normal or choice fill aligns the position, and an empty bounded, f32 normal or exponential fill leaves it.
• Odd n and the Box-Muller pair rule: CROSS_NORMAL32 and CROSS_NORMALF.
• Weighted choice: the tables and indices of all 24 cases, m = 1, and rejected weights.
• Boundaries: the SHA-256 of the twelve uniform streams and the FNV-1a and SHA-256 of the normal and exponential dumps (with std). Also a complex draw across a block, and start positions of 2^63 − 1, 2^63 and 2^64 − 1. Random access across rows and chunks is in tests/streams.rs.

A fill whose end reaches 2^64 cannot be expressed: starts lie below 2^63, and a slice cannot hold the 2^57 or more elements needed to reach 2^64 from there. The checklist of tandem-spec 2a4bd08 lets a port skip that item, and the test states what the crate does instead.

With std the normals and exponentials compare bit for bit. Without it they compare within the tolerance of Appendix A.

tests/derived.rs checks the derived draws against their definitions and laws: the bounded fills against Lemire's rule with the fallback, the f32 normal against the Box-Muller formula in f64, fills cut across their internal passes, the mean and variance of 2^20 normals, the Exp(1) moments to the fourth order with a Kolmogorov-Smirnov statistic on 1e7 samples, and a chi-square test of 1e6 weighted choices.

tests/rand_core.rs checks the trait implementations against the inherent API. tests/distr.rs (with --features rand) compares every distribution with its inherent draw on the conformance cases, sample_iter with the fills at lengths that cut their passes, and with std the two normal dump hashes. It also checks that a foreign generator gets normals of unit variance. tests/parallel.rs (with --features rayon) compares each parallel fill with the serial fill at offsets and lengths that cut rows and tasks, and checks the final position. tests/serde.rs (with --features serde) round-trips a generator through JSON and rejects a bad chunk length or start position. tests/intrinsics.rs (with --features simd-intrinsics) compares every fill with the stream built from the scalar block, at offsets and lengths that cut rows and chunks. tests/gpu.rs (with --features wgpu) compares GPU fills with the CPU fills over keys, chunk lengths, positions and lengths, and with the dumps. It skips without an adapter.

Fixtures

tests/conformance/*.json are byte-identical copies of tandem-spec 2a4bd08 conformance/*.json, generated by tandem-c 1c75956. CI compares them with the spec at 2a4bd08. tests/vectors_data/mod.rs is generated from the spec repository's vectors.json by tools/gen_vectors.py. tools/gen_zig_tables.py writes src/zig_tables.rs from the spec's tables/normal_f64_zig1024.json. CI checks that both are current. cargo run --release --example dump_normals | shasum -a 256 writes the same bytes as tandem-c's tools/dump_normals.c, and cargo run --release --example dump_exponentials | shasum -a 256 the same bytes as tandem-c's tools/dump_exponentials.c.