RSpec 'Expect' 语法和惯用属性规范

## 了解 RSpec 'Expect' 语法和惯用属性规范

ruby
class Calculator
  def add(a, b)
    a + b
  end
  def subtract(a, b)
    a - b
  end
end
RSpec.describe Calculator do
  let(:calc) { Calculator.new }
  context "加法方法" do
    it "正确计算两个数的和" do
      result = calc.add(3, 5)
      expect(result).to eq(8)
    end
    it "不应该返回错误的和" do
      result = calc.add(2, 3)
      expect(result).not_to eq(10)
    end
  end
  context "减法方法" do
    it "正确计算两个数的差" do
      result = calc.subtract(10, 4)
      expect(result).to eq(6)
    end
    it "不应该返回错误的差" do
      result = calc.subtract(7, 2)
      expect(result).not_to eq(1)
    end
  end
end