import { assert_true } from "https://deno.land/x/denops_std@v6.3.0/function/vim/mod.ts";
When {actual} is not true an error message is added to
v:errors, like with assert_equal().
Also see assert-return.
A value is TRUE when it is a non-zero number. When {actual}
is not a number the assert fails.
When {msg} is given it precedes the default message.
Can also be used as a method:
GetResult()->assert_true()