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_VBA_r2.m
    path of file: ./repos/VBA-toolbox/tests/utils
    
    the code of the file until where you have to start completion: function tests = test_VBA_r2
% Unit Tests for VBA_test_r2


    
function tests = test_VBA_r2
% Unit Tests for VBA_test_r2

tests = functiontests (localfunctions);

% inputs
function test_inputs (testCase)
    shouldFail = @() VBA_r2 (rand);
    testCase.verifyError(shouldFail, 'MATLAB:narginchk:notEnoughInputs');
    shouldFail = @() VBA_r2 (rand, rand, rand, rand);
    testCase.verifyError(shouldFail, 'MATLAB:TooManyInputs');
   
% catch overly simple cases
function test_empty (testCase)
    import matlab.unittest.constraints.*
    for k = 0 : 2
        actual = VBA_r2 (ones (1, k), ones (1, k));
        testCase.verifyEqual (actual, nan);
    end