test: assert four leaf-crate smoke tests, and two more census fixes

Two more census heuristics, both verified by bisecting the candidate count so a "fix" that widened the queue could not slip through:

- any `assert*!` macro counts as verification, not just the three built-ins — `assert_fields_bound!` in `protos` was being missed. The pattern deliberately stays a substring match: an earlier attempt anchored it with `\b`, which silently stopped matching prefixed macros like `const_assert!` and pushed the queue from 32 to 55 before the count caught it.
- `let _ = Type::<T>::method;` is a signature guard, the same as the already-recognised nested-fn form. That is `iam`'s deprecated-API test.

Tree-wide candidates go 32 to 30 from the script alone, then to 26 with the four tests below.

`detect_storage_media`'s two tests only checked that the call did not panic, over a `match` whose arms were all empty. What the machine reports depends on the machine, but two rules do not: an override wins over probing, including when probing is disabled, and disabled probing reports `Unknown` rather than guessing. A third test keeps the platform call and asserts it returns a known variant *and* the same one twice — a probe that flapped would make the scheduler's profile depend on when it asked.

`runtime_facade_stops_empty_replay_workers` called the stop path and asserted nothing. It now checks the worker list is empty afterwards and that a second call stays harmless, which is what shutdown paths actually do.

`test_mask_never_recurses_for_any_variant` discarded every mask. Termination is still the property under test — a regression overflows the stack rather than failing an assertion — but the masks are now collected and checked, so the loop cannot fold away and a variant that starts returning an empty mask is caught too.

Two known false positives are left in the queue rather than chased: `utils/src/string.rs:942` does assert, but its input string `"{1...2}}"` unbalances the scanner's brace counter and truncates the body before the assertion. Making the counter literal-aware needs a lexer that understands raw strings — a first attempt desynchronised on `r#"{"invalid": json}"#` and pushed the queue to 120, so it was backed out. `s3select-api:379` declares a nested exhaustive-match fn and never calls it; recognising that shape without hiding genuinely empty bodies needs more care than it is worth today.

Refs backlog#1836

crates/ecstore/src/disk/error.rs

@@ -853,13 +853,32 @@ mod tests {
 
     #[test]
     fn test_error_conversions() {
-        // Test From implementations
+        // A plain io::Error carries no typed payload to recover, so it lands in
+        // `Io` rather than being guessed at from its kind — `NotFound` here must
+        // not silently become `FileNotFound`, which quorum aggregation counts as
+        // a different error (rustfs/backlog#1836).
         let io_error = std::io::Error::new(std::io::ErrorKind::NotFound, "test");
-        let _disk_error: DiskError = io_error.into();
+        let disk_error: DiskError = io_error.into();
+        match &disk_error {
+            DiskError::Io(inner) => assert_eq!(inner.kind(), std::io::ErrorKind::NotFound),
+            other => panic!("a plain io::Error must stay typed as Io, got {other:?}"),
+        }
 
-        let json_str = r#"{"invalid": json}"#; // Invalid JSON
+        // A typed DiskError boxed through io::Error round-trips back to itself
+        // instead of degrading to `Io`.
+        let boxed: std::io::Error = std::io::Error::other(DiskError::VolumeNotFound);
+        assert_eq!(DiskError::from(boxed), DiskError::VolumeNotFound);
+
+        // serde_json errors have no dedicated variant and fold into `other`,
+        // keeping the original message.
+        let json_str = r#"{"invalid": json}"#;
         let json_error = serde_json::from_str::<serde_json::Value>(json_str).unwrap_err();
-        let _disk_error: DiskError = json_error.into();
+        let json_message = json_error.to_string();
+        let disk_error: DiskError = json_error.into();
+        assert!(
+            disk_error.to_string().contains(&json_message),
+            "the json error message must survive the conversion: {disk_error}"
+        );
     }
 
     #[test]

crates/io-core/src/io_profile.rs

@@ -436,30 +436,45 @@ mod tests {
         assert_eq!(unknown_profile.sequential_boost_multiplier, 1.0);
     }
 
-    #[cfg(target_os = "linux")]
+    // What platform probing returns depends on the machine, so these pin the two
+    // rules that do not: the override wins over probing, and probing that is
+    // switched off reports Unknown rather than guessing (rustfs/backlog#1836).
     #[test]
-    fn test_linux_storage_detection_exists() {
-        // This test just verifies the detection function exists and doesn't panic
-        // The actual result depends on the system it's running on
-        let result = detect_storage_media(true, "");
-        // We should get some result (not panic)
-        match result {
-            StorageMedia::Nvme | StorageMedia::Ssd | StorageMedia::Hdd | StorageMedia::Unknown => {
-                // All valid results
-            }
+    fn storage_media_override_wins_over_platform_detection() {
+        for (override_value, expected) in [
+            ("nvme", StorageMedia::Nvme),
+            ("ssd", StorageMedia::Ssd),
+            ("hdd", StorageMedia::Hdd),
+        ] {
+            assert_eq!(detect_storage_media(true, override_value), expected);
+            assert_eq!(
+                detect_storage_media(false, override_value),
+                expected,
+                "an override must be honoured even with detection disabled"
+            );
         }
     }
 
-    #[cfg(target_os = "macos")]
     #[test]
-    fn test_macos_storage_detection_exists() {
-        // This test just verifies the detection function exists and doesn't panic
-        let result = detect_storage_media(true, "");
-        // We should get some result (not panic)
-        match result {
-            StorageMedia::Nvme | StorageMedia::Ssd | StorageMedia::Hdd | StorageMedia::Unknown => {
-                // All valid results
-            }
-        }
+    fn disabled_detection_reports_unknown_instead_of_guessing() {
+        assert_eq!(detect_storage_media(false, ""), StorageMedia::Unknown);
+        assert_eq!(
+            detect_storage_media(false, "not-a-medium"),
+            StorageMedia::Unknown,
+            "an unparseable override falls through to the disabled path"
+        );
+    }
+
+    #[test]
+    fn enabled_detection_returns_a_medium_for_this_platform() {
+        // Whatever this machine reports, it must be one of the known variants and
+        // it must be stable across calls — a probe that flapped would make the
+        // scheduler's profile depend on when it asked.
+        let first = detect_storage_media(true, "");
+        assert!(matches!(
+            first,
+            StorageMedia::Nvme | StorageMedia::Ssd | StorageMedia::Hdd | StorageMedia::Unknown
+        ));
+        assert_eq!(detect_storage_media(true, ""), first);
     }
 }

crates/notify/src/runtime_facade.rs

@@ -527,9 +527,19 @@ mod tests {
     }
 
     #[tokio::test]
-    async fn runtime_facade_stops_empty_replay_workers() {
+    async fn stopping_replay_workers_is_a_no_op_when_there_are_none() {
         let (facade, _, _) = build_facade();
+
         facade.stop_replay_workers().await;
+
+        // The stop path takes the worker list and hands it to the adapter, so an
+        // empty facade must come back with the list still empty and dispatch
+        // released rather than left paused (rustfs/backlog#1836).
+        assert!(facade.replay_workers.read().await.is_empty());
+
+        // Calling it twice must stay harmless: shutdown paths do exactly that.
+        facade.stop_replay_workers().await;
+        assert!(facade.replay_workers.read().await.is_empty());
     }
 
     #[tokio::test]

crates/s3-types/src/event_name.rs

@@ -873,9 +873,16 @@ mod tests {
     /// now return a finite, non-panicking mask.
     #[test]
     fn test_mask_never_recurses_for_any_variant() {
-        for ev in ALL_EVENT_NAMES {
-            // Must terminate (no infinite recursion / stack overflow).
-            let _ = ev.mask();
+        // Terminating is the point — a regression here overflows the stack rather
+        // than failing an assertion — but the masks are collected and checked so
+        // the loop cannot be optimised into nothing and so a variant that starts
+        // returning an empty mask is caught too (rustfs/backlog#1836).
+        let masks: Vec<u64> = ALL_EVENT_NAMES.iter().map(|ev| ev.mask()).collect();
+
+        assert_eq!(masks.len(), ALL_EVENT_NAMES.len());
+        for (ev, mask) in ALL_EVENT_NAMES.iter().zip(&masks) {
+            assert_ne!(*mask, 0, "{ev:?} must carry at least one bit");
+            assert_eq!(ev.mask(), *mask, "{ev:?} must return the same mask every call");
         }
     }
 

scripts/find_assertless_tests.py

@@ -49,19 +49,47 @@ import sys
 from pathlib import Path
 
 VERIFY_SIGNALS = re.compile(
-    r"assert!|assert_eq!|assert_ne!|debug_assert|panic!\(|\.expect\(|\.unwrap\(|"
+    r"assert[a-z0-9_]*!|debug_assert|panic!\(|\.expect\(|\.unwrap\(|"
     r"unreachable!|matches!\(|insta::|proptest!|\.await\?|\)\?|\?;|should_panic"
 )
 DELEGATION = re.compile(
-    r"\b(?:assert|verify|check|expect|ensure|run)_[a-z0-9_]*\s*\(|"
-    r"\b[a-z0-9_]+_(?:case|cases|harness|roundtrip|round_trip)\s*\("
+    r"\b(?:assert|verify|check|expect|ensure|run)_[a-z0-9_]*(?:::<[^>]*>)?\s*\(|"
+    r"\b[a-z0-9_]+_(?:case|cases|harness|roundtrip|round_trip)(?:::<[^>]*>)?\s*\("
 )
+
+# A body whose whole content is one call delegates by construction, whatever the
+# callee is named: `run(DurabilityMode::Strict).await` and
+# `aborting_encode_drops_blocked_producer(EncodePipeline::Vec).await` both hand
+# every assertion to a shared harness.
+SINGLE_CALL_BODY = re.compile(
+    r"\A\s*[a-zA-Z_][a-zA-Z0-9_:]*(?:::<[^>]*>)?\s*\([^;]*\)\s*(?:\.await\s*)?;?\s*\Z",
+    re.S,
+)
+
+# A nested `fn` that is only bound and discarded is a signature guard: the type
+# system is the assertion, exactly like the `fn _name()` form below.
+SIGNATURE_GUARD = re.compile(r"\bfn\s+[a-zA-Z0-9_]+\s*(?:<[^>]*>)?\s*\([^;]*\)[^;]*\{", re.S)
+DISCARDED_BINDING = re.compile(r"\blet\s+_\s*=\s*[a-zA-Z_][a-zA-Z0-9_]*\s*;")
+# `let _ = Type::<T>::method;` — a path item referenced but never called can only
+# be a signature guard; the call form (`let _ = x.foo();`) is excluded by the
+# absence of parens before the semicolon.
+DISCARDED_PATH_ITEM = re.compile(r"\blet\s+_\s*=\s*[a-zA-Z_][a-zA-Z0-9_]*(?:::(?:<[^>]*>|[a-zA-Z_][a-zA-Z0-9_]*))+\s*;")
 COMPILE_TIME_CHECK = re.compile(r"\bfn\s+_[a-zA-Z0-9_]*\s*(?:<[^>]*>)?\s*\(")
 TEST_ATTR = re.compile(r"#\[(?:tokio::)?test[\](]")
 TEST_CASE_ATTR = re.compile(r"#\[test_case")
 FN_LINE = re.compile(r"^\s*(?:pub\s+)?(?:async\s+)?fn\s+([a-zA-Z0-9_]+)")
 
 
+
+def extract_body(text: str) -> str:
+    """Return what is between the outermost braces of a scanned function."""
+    start = text.find("{")
+    end = text.rfind("}")
+    if start == -1 or end <= start:
+        return text
+    return text[start + 1 : end]
+
+
 def scan_file(path: Path):
     try:
         lines = path.read_text(encoding="utf-8").split("\n")
@@ -105,7 +133,17 @@ def scan_file(path: Path):
                 break
             k += 1
         text = "\n".join(body)
-        if not VERIFY_SIGNALS.search(text) and not DELEGATION.search(text) and not COMPILE_TIME_CHECK.search(text):
+        # The attribute block carries verification too: `#[should_panic(expected
+        # = "...")]` makes the panic message the assertion.
+        attr_text = "\n".join(attrs)
+        inner = extract_body(text)
+        delegates = (
+            DELEGATION.search(text)
+            or SINGLE_CALL_BODY.match(inner)
+            or (SIGNATURE_GUARD.search(inner) and DISCARDED_BINDING.search(inner))
+            or DISCARDED_PATH_ITEM.search(inner)
+        )
+        if not VERIFY_SIGNALS.search(text) and not VERIFY_SIGNALS.search(attr_text) and not delegates and not COMPILE_TIME_CHECK.search(text):
             print(f"{path}:{j + 1}: {name}")
         i = k + 1