how can I add a column name as an argument to a function?

Question

Im creating a function to run cor.test for all the columns on a data frame, except the column that is added in the argument. I want the argument (ref) to be the column name, buy when I actually use ref in the cor.test, it says it needs to be a numeric vector. Don't know how to fix it

compute_cor_1 <- function(df, ref){
  all_cols <- names(df)
  except_col <- ref
  include_cols <- all_cols[all_col_ex != except_col]
  result <- matrix(NA, nrow = 1, ncol = length(include_cols))
  colnames(result) <- include_cols

  for(c_name in colnames(result)){
    result[,c_name] <- cor.test(df$ref, df[,c_name])$p.value
  }
  rownames(result) <- names(except_col)
  return(result)
}

compute_cor_1(test_data, c1) ## HERE I TRIED IT AND GIVES ERROR