replacing jsonb field value

using 9.4.2

suppose we have
create table test (id serial primary key, data jsonb);
insert into test (data) values ({"a":1, "b":2})

want to replace "b" with 3

okay, we are retrieving entire record
res = select * from test where data ->> b = 2

newrec = res
newrec["b" = 3

delete from test where data ->> b= 2
insert into test (data) values (newrec)

is this the best way until upsert arrives ?