marmelab/react-admin · error · Error

getOne is not implemented

Error message

getOne is not implemented

What it means

testDataProvider.ts defines a default DataProvider whose methods all throw 'not implemented' errors. This guards against tests accidentally relying on unimplemented data provider methods instead of mocking them via overrides.

Source

Thrown at packages/ra-core/src/dataProvider/testDataProvider.ts:32

        throw new Error('create is not implemented');
    },
    delete: async () => {
        throw new Error('delete not implemented');
    },
    deleteMany: async () => {
        throw new Error('deleteMany is not implemented');
    },
    getList: async () => {
        throw new Error('getList is not implemented');
    },
    getMany: async () => {
        throw new Error('getMany is not implemented');
    },
    getManyReference: async () => {
        throw new Error('getManyReference is not implemented');
    },
    getOne: async () => {
        throw new Error('getOne is not implemented');
    },
    update: async () => {
        throw new Error('update not implemented');
    },
    updateMany: async () => {
        throw new Error('updateMany not implemented');
    },
};
export const testDataProvider = (
    overrides?: Partial<DataProvider>
): DataProvider => ({
    ...defaultTestDataProvider,
    ...overrides,
});

View on GitHub (pinned to 051f511bb0)

Solutions

  1. Pass a getOne override: testDataProvider({ getOne: async () => ({ data: { id: 1 } }) })
  2. Avoid mounting components that call getOne, or mock the query so it never fires
  3. Use a full mock data provider instead of the default testDataProvider

Example fix

// before
const dataProvider = testDataProvider();
// after
const dataProvider = testDataProvider({
  getOne: async () => ({ data: { id: 1, title: 'Hello' } }),
});
Defensive patterns

Strategy: validation

Validate before calling

const dp = testDataProvider();
if (dp.getOne === defaultTestDataProvider.getOne) {
  throw new Error('testDataProvider.getOne must be overridden for this test');
}

Type guard

const hasGetOne = (dp: Partial<DataProvider>): dp is Partial<DataProvider> & Required<Pick<DataProvider, 'getOne'>> => typeof dp.getOne === 'function';

Try / catch

try {
  await dataProvider.getOne('posts', { id: 1 });
} catch (e) {
  if (e.message.includes('not implemented')) {
    // override missing in this test — fix the mock, not the test
  }
  throw e;
}

Prevention

When it happens

Trigger: Calling getOne on the default testDataProvider (or the provider returned by testDataProvider()) without passing a getOne override in the overrides object.

Common situations: Unit tests rendering react-admin components that fetch a single record (e.g. Edit, Show, useGetOne) while using testDataProvider without overriding getOne.

Related errors

AI-assisted analysis of marmelab/react-admin@051f511bb0 (2026-08-30). Data as JSON: /api/errors/52436eb64d19a165. Report an issue: GitHub.