internal/testlog: when instantiating new logger via With, set logger handler reference as the bufHandler in the newly-instantiated logger instead of copying from parent

internal/testlog/testlog.go

@@ -170,7 +170,8 @@ func (l *logger) Crit(msg string, ctx ...interface{}) {
 }
 
 func (l *logger) With(ctx ...interface{}) log.Logger {
-	return &logger{l.t, l.l.With(ctx...), l.mu, l.h}
+	newLogger := l.l.With(ctx...)
+	return &logger{l.t, newLogger, l.mu, newLogger.Handler().(*bufHandler)}
 }
 
 func (l *logger) New(ctx ...interface{}) log.Logger {

internal/testlog/testlog_test.go

@@ -0,0 +1,21 @@
+package testlog
+
+import (
+	"github.com/ethereum/go-ethereum/log"
+	"testing"
+)
+
+func TestLogging(t *testing.T) {
+	l := Logger(t, log.LevelInfo)
+	subLogger := l.New("foobar", 123)
+
+	l.Info("Visible")
+	subLogger.Info("Hide and seek") // not visible due to sub buffer never being flushed
+	l.Info("Also visible")
+
+	t.Log("flushed: ", l.Handler().(*bufHandler).buf)
+	t.Log("remaining: ", subLogger.Handler().(*bufHandler).buf)
+	// horrible hack to manually bring back the expected log data
+	l.Handler().(*bufHandler).buf = subLogger.Handler().(*bufHandler).buf
+	l.(*logger).flush()
+}