class RuboCop::Cop::Metrics::Utils::AbcSizeCalculator

the formula itself, is easier to test.
We separate the calculator from the cop so that the calculation,
> c2.com/cgi/wiki?AbcMetric<br>> of assignments, branches and conditions for a section of code.
> ABC is .. a software size metric .. computed by counting the number

def self.calculate(node) 

def self.calculate(node)
  new(node).calculate
end

def calculate 

def calculate
  @node.each_node do |child|
    if child.assignment?
      @assignment += 1
    elsif BRANCH_NODES.include?(child.type)
      evaluate_branch_nodes(child)
    elsif CONDITION_NODES.include?(child.type)
      @condition += 1 if node_has_else_branch?(child)
      @condition += 1
    end
  end
  Math.sqrt(@assignment**2 + @branch**2 + @condition**2).round(2)
end

def evaluate_branch_nodes(node) 

def evaluate_branch_nodes(node)
  if node.comparison_method?
    @condition += 1
  else
    @branch += 1
  end
end

def initialize(node) 

def initialize(node)
  @assignment = 0
  @branch = 0
  @condition = 0
  @node = node
end

def node_has_else_branch?(node) 

def node_has_else_branch?(node)
  %i[case if].include?(node.type) &&
    node.else? &&
    node.loc.else.is?('else')
end