F-tools: the runner's views consumer is proven on the real bus; the heartbeat is asked of the bus only when a bundle wants it, with no race; a seat record says when the bus wrote it; the beat test counts ticks, not sleeps

Claude-Session: https://claude.ai/code/session_01JG73KJNrH5EgFXMKKYSrig

node-tools/internal/runtime/events_test.go

@@ -1,11 +1,13 @@
 package runtime
 
 import (
+	"encoding/json"
 	"fmt"
 	"os"
 	"path/filepath"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -157,3 +159,30 @@ func TestALongRunningBundleThatExitsIsStartedAgain(t *testing.T) {
 
 func fmtSprintf(format string, args ...any) string { return fmt.Sprintf(format, args...) }
 func errorf(format string, args ...any) error      { return fmt.Errorf(format, args...) }
+
+// A bundle loaded again sets its heartbeat handler while the consumer's loop hands a word on: no data race (-race),
+// and the heartbeat is asked of the bus only while some bundle holds a handler.
+func TestAHeartbeatHandlerSetAgainWhileWordsAreHandedOnIsNotARace(t *testing.T) {
+	m := &moduleEvents{}
+	all := &consumers{logf: t.Logf, of: map[string]*moduleEvents{"mod": m}}
+	slot := &beatSlot{}
+	m.beats = []*beatSlot{slot}
+	if m.beatAsked() {
+		t.Fatal("a heartbeat is asked while no bundle gave a handler")
+	}
+	var got atomic.Int32
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		for i := 0; i < 200; i++ {
+			slot.set(func(json.RawMessage) { got.Add(1) })
+		}
+	}()
+	for i := 0; i < 200; i++ {
+		all.handBeat(m, bus.Beat{At: time.Now()})
+	}
+	<-done
+	if !m.beatAsked() {
+		t.Error("a bundle gave a handler and no heartbeat is asked")
+	}
+}