bytes and strings tests pass, with disclosed-divergence
Full text of the July 18, 2026 announcement, condensed in the go2cs News Archive.
Two more standard-library packages validate their own Go test suites in C# — and they arrive with a
new piece of Phase-4 machinery. bytes
validates 81 tests and strings
68 against go test -json, bringing the count of Phase-4-validated packages to four (after
unicode/utf8 and sort).
Both packages contain a handful of tests that assert an exact allocation count via Go’s
testing.AllocsPerRun — for example, strings’s TestBuilderAllocs insists a Builder heap-allocates
exactly once. These are unsatisfiable by design in a managed runtime: the CLR has no malloc counter (the
shim measures allocated bytes instead), and .NET genuinely allocates where Go’s escape analysis
stack-allocates — an addressed var b Builder heap-boxes per run; string(r) materializes a byte[]
where Go uses a 4-byte stack buffer. A malloc-counting shim would fail these identically; the divergence
is the allocation model, not the measurement.
Rather than silently skip them, go2cs now discloses them at test level. Each affected package carries a
hand-owned, repo-committed go2cs_test_disclosures.json — reviewed like source, never generated — that
pins {test, divergence class, expected failure signature}. The differential oracle reclassifies a
Go-passes/C#-fails result as disclosed-divergent only when both the test name and the pinned failure
signature match; a disclosed test that fails any other way is still a hard mismatch, so the pin is an
integrity guard, not a blanket exemption. The validation summary reports the reclassified rows explicitly
(… 7 disclosed-divergent (alloc-profile), …). Packages without a manifest — sort and utf8 —
compare strictly and are wholly unaffected.
Phase-4 packages #3 and #4 · sort 63/63, bytes 81, strings 68 · reproduce from a clone via
Try it yourself