当组件有多个 useQuery 时，Apollo 的 MockedProvider 是否可以工作？

Question

我设置了一个简单的 Apollo。在此 CodeSandbox 示例中，我使用的是， MockedProvider但实时版本也可以使用：

https://codesandbox.io/s/winter-glitter-o8ug5?file=/src/App.js:0-1164

import { ApolloClient, InMemoryCache } from "@apollo/client";
import { gql, useQuery, ApolloProvider } from "@apollo/client";
import { MockedProvider } from "@apollo/client/testing";

const client = new ApolloClient({
  uri: "https://48p1r2roz4.sse.codesandbox.io",
  cache: new InMemoryCache()
});

const EXCHANGE_RATES_1 = gql`
  query GetExchangeRates {
    rates(currency: "USD") {
      rate
    }
  }
`;

const mocks = [
  {
    request: {
      query: EXCHANGE_RATES_1
    },
    result: {
      data: {
        rates: [
          {
            __typename: "ExchangeRate",
            rate: "123"
          }
        ]
      }
    }
  }
];

const MyComponent = () => {
  const { data: data1, loading: loading1 } = useQuery(EXCHANGE_RATES_1);
  if (loading1) return <p>Loading...</p>;
  return (
    <div>
      <h1>{data1?.rates[0].rate}</h1>
    </div>
  );
};

const AppMocked = () => {
  return (
    <MockedProvider addTypename={false} mocks={mocks}>
      <MyComponent />
    </MockedProvider>
  );
};

const AppLive = () => {
  return (
    <ApolloProvider client={client}>
      <MyComponent />
    </ApolloProvider>
  );
};

export default AppMocked;

我需要有一个额外useQuery的MyComponent. 我知道这是一个奇怪的例子，因为它应该只是一个查询，但它说明了我遇到的问题。

https://codesandbox.io/s/magical-dewdney-j451d?file=/src/App.js:0-1630

import { ApolloClient, InMemoryCache } from "@apollo/client";
import { gql, useQuery, ApolloProvider } from "@apollo/client";
import { MockedProvider } from "@apollo/client/testing";

const client = new ApolloClient({
  uri: "https://48p1r2roz4.sse.codesandbox.io",
  cache: new InMemoryCache()
});

const EXCHANGE_RATES_1 = gql`
  query GetExchangeRates {
    rates(currency: "USD") {
      rate
    }
  }
`;
const EXCHANGE_RATES_2 = gql`
  query GetExchangeRates {
    rates(currency: "USD") {
      currency
    }
  }
`;

const mocks = [
  {
    request: {
      query: EXCHANGE_RATES_1
    },
    result: {
      data: {
        rates: [
          {
            __typename: "ExchangeRate",
            rate: "123"
          }
        ]
      }
    }
  },
  {
    request: {
      query: EXCHANGE_RATES_2
    },
    result: {
      data: {
        rates: [
          {
            __typename: "ExchangeRate",
            currency: "YOLO"
          }
        ]
      }
    }
  }
];

const MyComponent = () => {
  const { data: data1, loading: loading1 } = useQuery(EXCHANGE_RATES_1);
  const { data: data2, loading: loading2 } = useQuery(EXCHANGE_RATES_2);
  if (loading1 || loading2) return <p>Loading...</p>;
  return (
    <div>
      <h1>{data1?.rates[0].rate}</h1>
      <h2>{data2?.rates[0].currency}</h2>
    </div>
  );
};

const AppMocked = () => {
  return (
    <MockedProvider addTypename={false} mocks={mocks}>
      <MyComponent />
    </MockedProvider>
  );
};

const AppLive = () => {
  return (
    <ApolloProvider client={client}>
      <MyComponent />
    </ApolloProvider>
  );
};

export default AppMocked;

现场版本工作正常，但模拟版本有一个空的 H1。当我注销时，data1我可以看到它最初确实有数据，但在后续渲染中变成“未定义”

我在文档中看不到任何内容来解释为什么模拟不起作用：https://www.apollographql.com/docs/react/development-testing/testing/

Answer 1

由于某种原因，在您的设置中，查询被多次调用。

这会在幕后导致“不再有查询的模拟响应”错误（请参阅mockLink.ts），因为每个查询调用都会消耗一个模拟响应。
第一次调用查询时，它会返回模拟数据，这就是您最初看到它的原因。但下一个调用会抛出错误并将数据设置为undefined。

我找到了两种方法来解决这个问题：

选项 1fetch-policy通过将以下设置禁用 MockedProvider 上的缓存no-cache：

<MockedProvider 
  mocks={mocks} 
  defaultOptions={{
    watchQuery: { fetchPolicy: 'no-cache' },
    query: { fetchPolicy: 'no-cache' },
  }}
>
  <MyComponent />
</MockedProvider>

选项 2通过提供函数允许多次使用模拟响应newData：

const mocks = [
  {
    request: {
      query: EXCHANGE_RATES_1
    },
    result: {
      data: {
        rates: [
          {
            __typename: "ExchangeRate",
            rate: "123"
          }
        ]
      }
    },
    newData: () => ({
      data: {
        rates: [
          {
            __typename: "ExchangeRate",
            rate: "123"
          }
        ]
      }
    })
  },
  {
    request: {
      query: EXCHANGE_RATES_2
    },
    result: {
      data: {
        rates: [
          {
            __typename: "ExchangeRate",
            currency: "YOLO"
          }
        ]
      }
    },
    newData: () => ({
      data: {
        rates: [
          {
            __typename: "ExchangeRate",
            currency: "YOLO"
          }
        ]
      }
    })
  }
];