The exact multinomial goodness of fit test for whether a set of counts fits a hypothetical distribution. counts is an input range of counts. proportions is an input range of expected proportions. These are normalized automatically, so they can sum to any value.
The P-value for the null that counts is a sample from proportions against the alternative that it isn't.
Notes: This test is EXTREMELY slow for anything but very small samples and degrees of freedom. The Pearson's chi-square (chiSquareFit()) or likelihood ratio chi-square (gTestFit()) are good enough approximations unless sample size is very small.