这是使用let或let!时的预期行为。它的值将被存储为一个期望值（一个it块）。
如果你想避免为每个测试重新创建supplier，那么我看到了两个选项：
1.把所有的期望合二为一

let(:supplier) { create(:supplier) }

shared_examples 'a product not in stock with supplier' do |products|
  it 'raises an error' do
    products.each do |product|
      expect { 
        described_class.dispatch_product!(supplier, product) 
      }.to raise_error 'Product is not in stock'
    end
  end
end

context 'when the state is not supported' do
  it_behaves_like 'a product not in stock with supplier', 
                  [Chair_1, Table_1, Sofa_1]
end

1.您将示例存储在示例变量中并手动处理它

shared_examples 'a product not in stock with supplier' do |product|
  it 'raises an error' do
    expect { 
      described_class.dispatch_product!(supplier, product) 
    }.to raise_error 'Product is not in stock'
  end
end

context 'when the state is not supported' do
  before(:context) { @supplier ||= create(:supplier) }

  it_behaves_like 'a product not in stock with supplier', 
                  Chair_1 { let(:supplier) { @supplier } }
  it_behaves_like 'a product not in stock with supplier', 
                  Table_1 { let(:supplier) { @supplier } }
  it_behaves_like 'a product not in stock with supplier', 
                  Sofa_1 { let(:supplier) { @supplier } }
end

我不喜欢这些选项中的任何一个，我认为它们使规范更难阅读，并且是RSpec默认行为和设计原则的丑陋解决方案。
在这种情况下，除了在工厂中使用Fixtures之外，您可能还需要考虑在测试中使用Fixtures。如果您只为一个供应商创建了一个默认的fixture，那么您可以为所有类型的测试重用同一个供应商，在这些测试中，您不关心使用具有任何特定配置的供应商。
如果你在应用中配置了一个fixture，并且有一个有效的suppliers(:default) fixture，那么它可能看起来像这样：

let(:supplier) { suppliers(:default) } # would reuse the same instance from the db

shared_examples 'a product not in stock with supplier' do |product|
  it 'raises an error' do
    expect { 
      described_class.dispatch_product!(supplier, product) 
    }.to raise_error 'Product is not in stock'
  end
end

context 'when the state is not supported' do
  it_behaves_like 'a product not in stock with supplier', Chair_1
  it_behaves_like 'a product not in stock with supplier', Table_1
  it_behaves_like 'a product not in stock with supplier', Sofa_1
end