log/slog — validation proof

Go’s own log/slog test suite, converted to C# by go2cs, built against the converted standard library, run under the Go-semantics test host, and compared verdict for verdict against a clean go test -json baseline of the same sources. This page is generated by the converter from that comparison — it is the evidence behind the log/slog row in Validated Test Packages.

Validated 2026-09-23 · converter f95f88866

197 matched · 19 disclosed — Go 1.24.13, windows/amd64, converted package src/core/log/slog.

Measured at Release (tiered JIT on), oracle go version go1.24.13 windows/amd64.

Verdicts

Test go test go2cs
TestAliasingAndClone pass pass
TestAlloc pass fail (disclosed)
TestAlloc/2_pairs pass fail (disclosed)
TestAlloc/2_pairs_disabled pass pass
TestAlloc/2_pairs_disabled_inline pass fail (disclosed)
TestAlloc/9_kvs pass fail (disclosed)
TestAlloc/Error pass fail (disclosed)
TestAlloc/Info pass fail (disclosed)
TestAlloc/attrs1 pass fail (disclosed)
TestAlloc/attrs3 pass fail (disclosed)
TestAlloc/attrs3_disabled pass fail (disclosed)
TestAlloc/attrs6 pass fail (disclosed)
TestAlloc/attrs9 pass fail (disclosed)
TestAlloc/logger.Info pass fail (disclosed)
TestAlloc/logger.Log pass fail (disclosed)
TestAlloc/pairs pass fail (disclosed)
TestAnyLevelAlloc pass fail (disclosed)
TestAnyValue pass pass
TestAppendJSONValue pass pass
TestAttrNoAlloc pass fail (disclosed)
TestAttrs pass pass
TestCallDepth pass pass
TestConcurrentWrites pass pass
TestConcurrentWrites/json pass pass
TestConcurrentWrites/text pass pass
TestConnections pass pass
TestConnections/wrap_default_handler pass pass
TestContext pass pass
TestDefaultHandle pass pass
TestDefaultHandle/attrs pass pass
TestDefaultHandle/group pass pass
TestDefaultHandle/groups pass pass
TestDefaultHandle/no_attrs pass pass
TestDefaultHandle/preformatted pass pass
TestDefaultHandle/preformatted_groups pass pass
TestDefaultHandle/two_with-groups pass pass
TestDiscardHandler pass pass
TestEmptyGroup pass pass
TestHandlerEnabled pass pass
TestJSONAndTextHandlers pass pass
TestJSONAndTextHandlers/GroupValue_as_Attr_value pass pass
TestJSONAndTextHandlers/GroupValue_as_Attr_value/json pass pass
TestJSONAndTextHandlers/GroupValue_as_Attr_value/text pass pass
TestJSONAndTextHandlers/LogValuer pass pass
TestJSONAndTextHandlers/LogValuer/json pass pass
TestJSONAndTextHandlers/LogValuer/text pass pass
TestJSONAndTextHandlers/Source pass pass
TestJSONAndTextHandlers/Source/json pass pass
TestJSONAndTextHandlers/Source/text pass pass
TestJSONAndTextHandlers/basic pass pass
TestJSONAndTextHandlers/basic/json pass pass
TestJSONAndTextHandlers/basic/text pass pass
TestJSONAndTextHandlers/byte_slice pass pass
TestJSONAndTextHandlers/byte_slice/json pass pass
TestJSONAndTextHandlers/byte_slice/text pass pass
TestJSONAndTextHandlers/cap_keys pass pass
TestJSONAndTextHandlers/cap_keys/json pass pass
TestJSONAndTextHandlers/cap_keys/text pass pass
TestJSONAndTextHandlers/empty_group pass pass
TestJSONAndTextHandlers/empty_group/json pass pass
TestJSONAndTextHandlers/empty_group/text pass pass
TestJSONAndTextHandlers/empty_key pass pass
TestJSONAndTextHandlers/empty_key/json pass pass
TestJSONAndTextHandlers/empty_key/text pass pass
TestJSONAndTextHandlers/empty_with-groups pass pass
TestJSONAndTextHandlers/empty_with-groups,_no_non-empty_attrs pass pass
TestJSONAndTextHandlers/empty_with-groups,_no_non-empty_attrs/json pass pass
TestJSONAndTextHandlers/empty_with-groups,_no_non-empty_attrs/text pass pass
TestJSONAndTextHandlers/empty_with-groups/json pass pass
TestJSONAndTextHandlers/empty_with-groups/text pass pass
TestJSONAndTextHandlers/escapes pass pass
TestJSONAndTextHandlers/escapes/json pass pass
TestJSONAndTextHandlers/escapes/text pass pass
TestJSONAndTextHandlers/groups pass pass
TestJSONAndTextHandlers/groups/json pass pass
TestJSONAndTextHandlers/groups/text pass pass
TestJSONAndTextHandlers/inline_group pass pass
TestJSONAndTextHandlers/inline_group/json pass pass
TestJSONAndTextHandlers/inline_group/text pass pass
TestJSONAndTextHandlers/json.RawMessage pass pass
TestJSONAndTextHandlers/json.RawMessage/json pass pass
TestJSONAndTextHandlers/json.RawMessage/text pass pass
TestJSONAndTextHandlers/nested_empty_group pass pass
TestJSONAndTextHandlers/nested_empty_group/json pass pass
TestJSONAndTextHandlers/nested_empty_group/text pass pass
TestJSONAndTextHandlers/nested_non-empty_group pass pass
TestJSONAndTextHandlers/nested_non-empty_group/json pass pass
TestJSONAndTextHandlers/nested_non-empty_group/text pass pass
TestJSONAndTextHandlers/one_empty_with-group pass pass
TestJSONAndTextHandlers/one_empty_with-group/json pass pass
TestJSONAndTextHandlers/one_empty_with-group/text pass pass
TestJSONAndTextHandlers/preformatted pass pass
TestJSONAndTextHandlers/preformatted/json pass pass
TestJSONAndTextHandlers/preformatted/text pass pass
TestJSONAndTextHandlers/preformatted_cap_keys pass pass
TestJSONAndTextHandlers/preformatted_cap_keys/json pass pass
TestJSONAndTextHandlers/preformatted_cap_keys/text pass pass
TestJSONAndTextHandlers/preformatted_remove_all pass pass
TestJSONAndTextHandlers/preformatted_remove_all/json pass pass
TestJSONAndTextHandlers/preformatted_remove_all/text pass pass
TestJSONAndTextHandlers/preformatted_remove_built-in pass pass
TestJSONAndTextHandlers/preformatted_remove_built-in/json pass pass
TestJSONAndTextHandlers/preformatted_remove_built-in/text pass pass
TestJSONAndTextHandlers/preformatted_with-groups pass pass
TestJSONAndTextHandlers/preformatted_with-groups/json pass pass
TestJSONAndTextHandlers/preformatted_with-groups/text pass pass
TestJSONAndTextHandlers/remove_all pass pass
TestJSONAndTextHandlers/remove_all/json pass pass
TestJSONAndTextHandlers/remove_all/text pass pass
TestJSONAndTextHandlers/remove_built-in pass pass
TestJSONAndTextHandlers/remove_built-in/json pass pass
TestJSONAndTextHandlers/remove_built-in/text pass pass
TestJSONAndTextHandlers/replace_built-in_with_group pass pass
TestJSONAndTextHandlers/replace_built-in_with_group/json pass pass
TestJSONAndTextHandlers/replace_built-in_with_group/text pass pass
TestJSONAndTextHandlers/replace_empty pass pass
TestJSONAndTextHandlers/replace_empty/json pass pass
TestJSONAndTextHandlers/replace_empty/text pass pass
TestJSONAndTextHandlers/replace_empty_1 pass pass
TestJSONAndTextHandlers/replace_empty_1/json pass pass
TestJSONAndTextHandlers/replace_empty_1/text pass pass
TestJSONAndTextHandlers/replace_empty_2 pass pass
TestJSONAndTextHandlers/replace_empty_2/json pass pass
TestJSONAndTextHandlers/replace_empty_2/text pass pass
TestJSONAndTextHandlers/replace_empty_3 pass pass
TestJSONAndTextHandlers/replace_empty_3/json pass pass
TestJSONAndTextHandlers/replace_empty_3/text pass pass
TestJSONAndTextHandlers/replace_empty_inline pass pass
TestJSONAndTextHandlers/replace_empty_inline/json pass pass
TestJSONAndTextHandlers/replace_empty_inline/text pass pass
TestJSONAndTextHandlers/replace_partial_empty_attrs_1 pass pass
TestJSONAndTextHandlers/replace_partial_empty_attrs_1/json pass pass
TestJSONAndTextHandlers/replace_partial_empty_attrs_1/text pass pass
TestJSONAndTextHandlers/replace_partial_empty_attrs_2 pass pass
TestJSONAndTextHandlers/replace_partial_empty_attrs_2/json pass pass
TestJSONAndTextHandlers/replace_partial_empty_attrs_2/text pass pass
TestJSONAndTextHandlers/replace_partial_empty_attrs_3 pass pass
TestJSONAndTextHandlers/replace_partial_empty_attrs_3/json pass pass
TestJSONAndTextHandlers/replace_partial_empty_attrs_3/text pass pass
TestJSONAndTextHandlers/replace_resolved_group pass pass
TestJSONAndTextHandlers/replace_resolved_group/json pass pass
TestJSONAndTextHandlers/replace_resolved_group/text pass pass
TestJSONAndTextHandlers/resolve pass pass
TestJSONAndTextHandlers/resolve/json pass pass
TestJSONAndTextHandlers/resolve/text pass pass
TestJSONAndTextHandlers/two_with-groups pass pass
TestJSONAndTextHandlers/two_with-groups/json pass pass
TestJSONAndTextHandlers/two_with-groups/text pass pass
TestJSONAndTextHandlers/with-group pass pass
TestJSONAndTextHandlers/with-group/json pass pass
TestJSONAndTextHandlers/with-group/text pass pass
TestJSONAppendAttrValueSpecial pass pass
TestJSONHandler pass pass
TestJSONHandler/none pass pass
TestJSONHandler/replace pass pass
TestKindString pass pass
TestLevelAppendText pass pass
TestLevelFlag pass pass
TestLevelMarshalJSON pass pass
TestLevelMarshalText pass pass
TestLevelParse pass pass
TestLevelParseError pass pass
TestLevelString pass pass
TestLevelVar pass pass
TestLevelVarAppendText pass pass
TestLevelVarFlag pass pass
TestLevelVarMarshalText pass pass
TestLevelVarString pass pass
TestLogLoggerLevelForDefaultHandler pass pass
TestLogLoggerLevelForHandlerWriter pass pass
TestLogTextHandler pass pass
TestLogValue pass pass
TestLoggerError pass pass
TestLoggerNoOps pass pass
TestNeedsQuoting pass pass
TestNewLogLogger pass pass
TestPanics pass pass
TestRecordAttrs pass pass
TestRecordSource pass fail (disclosed)
TestReplaceAttrGroups pass pass
TestSecondWith pass pass
TestSetAttrs pass pass
TestSetDefault pass pass
TestSlogtest pass pass
TestSlogtest/JSON pass pass
TestSlogtest/Text pass pass
TestTextHandler pass pass
TestTextHandler/String_method pass pass
TestTextHandler/String_method/none pass pass
TestTextHandler/String_method/replace pass pass
TestTextHandler/TextMarshaler pass pass
TestTextHandler/TextMarshaler/none pass pass
TestTextHandler/TextMarshaler/replace pass pass
TestTextHandler/TextMarshaler_error pass pass
TestTextHandler/TextMarshaler_error/none pass pass
TestTextHandler/TextMarshaler_error/replace pass pass
TestTextHandler/nil_value pass pass
TestTextHandler/nil_value/none pass pass
TestTextHandler/nil_value/replace pass pass
TestTextHandler/quoted pass pass
TestTextHandler/quoted/none pass pass
TestTextHandler/quoted/replace pass pass
TestTextHandler/struct pass pass
TestTextHandler/struct/none pass pass
TestTextHandler/struct/replace pass pass
TestTextHandler/unquoted pass pass
TestTextHandler/unquoted/none pass pass
TestTextHandler/unquoted/replace pass pass
TestTextHandlerAlloc pass fail (disclosed)
TestTextHandlerPreformatted pass pass
TestValueAny pass pass
TestValueEqual pass pass
TestValueNoAlloc pass fail (disclosed)
TestValueString pass pass
TestValueTime pass pass
TestWriteTimeRFC3339 pass pass

Disclosed divergences

A disclosed divergence is a specific Go assertion this conversion does not satisfy — not a skipped test and not a tolerance. Each one is pinned by exact failure signature in the package’s hand-owned go2cs_test_disclosures.json; a disclosed test that fails any other way is still a hard mismatch.

The Class column says which kind each one is: a deferred entry is an assertion the managed CLR can meet, pinned against the named plan that will retire it; every other class is one it provably cannot satisfy.

Test Class Pinned reason
TestAlloc aggregate no failure text of its own — the roll-up of this test’s disclosed subtests
TestAlloc/2_pairs deferred wantAllocs assert with a NONZERO Go budget (2): the managed model pays a heap shell per boxed pair on top of Go’s two budgeted allocations, so the divergence is the shell count rather than the assert’s premise. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1); it replaces the ruling’s fitted F6/F7 for this row: F6 is the per-call literal (the converter’s degenerate-slug floor, hoistedLiteralOperations.go:103) and F7 the StringData element reference.
TestAlloc/2_pairs_disabled_inline deferred wantAllocs assert with a nonzero Go budget: even on the level-disabled path the ...any arguments are boxed before the level check can discard them, where Go’s interface values cost nothing to form. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1); it replaces the ruling’s fitted F6/F7 for this row: F6 is the per-call literal (the converter’s degenerate-slug floor, hoistedLiteralOperations.go:103) and F7 the StringData element reference.
TestAlloc/9_kvs deferred wantAllocs assert with a nonzero Go budget (10): nine key/value pairs box into nine heap shells above Go’s budgeted slice growth. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1); it replaces the ruling’s fitted F6/F7 for this row: F6 is the per-call literal (the converter’s degenerate-slug floor, hoistedLiteralOperations.go:103) and F7 the StringData element reference.
TestAlloc/Error deferred wantAllocs assert: same ...any boxing as TestAlloc/Info on the Error level path — one heap shell per argument where Go’s interface value allocates nothing. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1).
TestAlloc/Info deferred wantAllocs assert: the variadic ...any argument list boxes each value into a heap shell where Go’s interface value is two words carrying the data pointer inline (DESIGN-iface-shell-caching §2 — ‘C# has no two-word interface value; the shell IS the itab+data fused into an object’). RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1).
TestAlloc/attrs1 deferred wantAllocs assert: constructing one Attr materializes a boxed Value in the managed model where Go’s Value packs the payload into its own struct fields. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1); it replaces the ruling’s fitted F6/F7 for this row: F6 is the per-call literal (the converter’s degenerate-slug floor, hoistedLiteralOperations.go:103) and F7 the StringData element reference.
TestAlloc/attrs3 deferred wantAllocs assert: three Attrs, each carrying a boxed Value shell that Go’s packed Value representation does not allocate. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1); it replaces the ruling’s fitted F6/F7 for this row: F6 is the per-call literal (the converter’s degenerate-slug floor, hoistedLiteralOperations.go:103) and F7 the StringData element reference.
TestAlloc/attrs3_disabled deferred wantAllocs assert: the Attrs are constructed — and therefore boxed — before the level check discards them, so the level-disabled path allocates in the managed model exactly as the enabled one does. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1); it replaces the ruling’s fitted F6/F7 for this row: F6 is the per-call literal (the converter’s degenerate-slug floor, hoistedLiteralOperations.go:103) and F7 the StringData element reference.
TestAlloc/attrs6 deferred wantAllocs assert with a nonzero Go budget (1): six Attrs box six Values above Go’s single budgeted allocation. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1); it replaces the ruling’s fitted F6/F7 for this row: F6 is the per-call literal (the converter’s degenerate-slug floor, hoistedLiteralOperations.go:103) and F7 the StringData element reference.
TestAlloc/attrs9 deferred wantAllocs assert with a nonzero Go budget (1): nine Attrs box nine Values above Go’s single budgeted allocation. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1); it replaces the ruling’s fitted F6/F7 for this row: F6 is the per-call literal (the converter’s degenerate-slug floor, hoistedLiteralOperations.go:103) and F7 the StringData element reference.
TestAlloc/logger.Info deferred wantAllocs assert: the Logger.Info convenience path boxes its ...any arguments into heap shells where Go passes two-word interface values. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1).
TestAlloc/logger.Log deferred wantAllocs assert: the Logger.Log path boxes its ...any arguments into heap shells where Go passes two-word interface values. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1).
TestAlloc/pairs deferred wantAllocs assert: each key/value pair boxes through any into a heap shell; Go’s escape analysis keeps the equivalent interface values off the heap entirely. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1).
TestAnyLevelAlloc deferred wantAllocs assert: passing a Level through any boxes the value type into a heap shell, which is precisely the allocation Go’s two-word interface value avoids. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1).
TestAttrNoAlloc deferred want-zero AllocsPerRun assert: each Attr constructor boxes its payload into a Value shell in the managed model, where Go’s Value stores the payload inline in the struct and allocates nothing. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1); it replaces the ruling’s fitted F6/F7 for this row: F6 is the per-call literal (the converter’s degenerate-slug floor, hoistedLiteralOperations.go:103) and F7 the StringData element reference.
TestRecordSource host-identity the depth-2 sub-case asserts that two frames above the test function sits testing.tRunner in testing.go — Go’s own test binary, whose testing package is compiled from that source. The converted host is the hand-owned structural replacement (F15b): its runner lives in go.testing_runtime, so it is not a converted-Go frame at all and never enters the projected traceback, and it carries no position-map record, so its file half could only ever be .cs. Passing would require the host to claim testing/testing.go, which the standing position-map ruling forbids. The depth-1 sub-case of this SAME test asserts log/slog.TestRecordSource and passes — that was the internal-test-variant caller-info defect, fixed 2026-08-26 rather than disclosed, which is what fixes this class’s boundary: only the host’s own frame is disclosed here
TestTextHandlerAlloc deferred wantAllocs assert: TextHandler.Handle formats through boxed Values and an interface-typed Handler, so the append-only formatting path Go performs allocation-free pays one heap shell per attribute here. RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading.
TestValueNoAlloc deferred want-zero AllocsPerRun assert: every Value constructor boxes through any into a heap shell, the direct managed counterpart of Go’s inline-payload Value (DESIGN-iface-shell-caching §2 — the shell IS the interface value, and nothing short of IDynamicInterfaceCastable removes it). RELABEL 2026-09-23 (C1, as ruled at ledger 2026-09-23 03:37 O2): alloc-profile -> deferred. The boxing/shell proof above is WITHDRAWN: the counter never charges a CLR box or an interface shell (AllocationCounter.cs:50-53), so it cannot explain a COUNT reading. The composition in the plan was READ in the emission at bb54ff0920 (C1); it replaces the ruling’s fitted F6/F7 for this row: F6 is the per-call literal (the converter’s degenerate-slug floor, hoistedLiteralOperations.go:103) and F7 the StringData element reference.

Excluded declarations

Declarations filtered from both sides of the comparison, and therefore not claimed above: Benchmark, Fuzz and Example declarations the converted host does not execute, plus any test requiring a capability the managed runtime does not provide — a testing member the host has not implemented, or a platform behavior it provably cannot reproduce. Each is named with the capability it needs.