如何更新每个rspec测试的值？

RSpec.describe MyClass do
  let(:my_variable) { 10 }

  it "测试1" do
    expect(my_variable).to eq(10)
    my_variable = 20
    expect(my_variable).to eq(20)
  end

  it "测试2" do
    expect(my_variable).to eq(10)
  end
end

RSpec.describe MyClass do
  let!(:my_variable) { 10 }

  it "测试1" do
    expect(my_variable).to eq(10)
    my_variable = 20
    expect(my_variable).to eq(20)
  end

  it "测试2" do
    expect(my_variable).to eq(20)
  end
end