len(s0),
			s0,
		},
		{
			"WriteRune",
			func(b *Builder) (int, error) { return b.WriteRune('a') },
			1,
			"a",
		},
		{
			"WriteRuneWide",
			func(b *Builder) (int, error) { return b.WriteRune('世') },
			3,
			"世",
		},
		{
			"WriteString",
			func(b *Builder) (int, error) { return b.WriteString(s0) },
			len(s0),
			s0,
		},