You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: test_plus.m
    path of file: ./repos/chebfun/tests/chebfun2
    
    the code of the file until where you have to start completion: function pass = test_plus( pref ) 
% This tests the basic arithmetic operations on chebfun2 objects.

if ( nargin < 1 ) 
    
function with a small vscale works: 
f = chebfun2(@(x,y) 1e-100*x); 
g = f + f; 
pass(5) = ( length(g) == length(f) ); 
pass(6) = ( abs( vscale( g ) - 2e-100 ) < tol ); 

% Check adding a function with a large vscale works: 
f = chebfun2(@(x,y) 1e100*x); 
g = f + f; 
pass(7) = ( length(g) == length(f) ); 
pass(8) = ( abs( vscale( g ) - 2e100 )/2e100 < 2e-2 ); 

end