I’ve got code that uses GetItemCommand to get data from my DynamoDb instance, however I’m not entirely sure how I go about testing my function that uses it.

I don’t want to test the GetItemCommand itself, I just want to mock out the value it returns.

db.ts:

export const getFromDb = async (id) => {
  const command = new GetItemCommand({
    TableName: 'table-name',
    Key: {
      ID: { S: id },
    },
  });

  try {
    return await client.send(command);
  } catch (err) {
    // do something
  }
};

function.ts:

export const doStuff = async () => {
  ...

  const dbData: GetItemCommandOutput = await getFromDb(id);
  if (!dbData.Item) throw Error("no record found");
  ...
}

So far I have tried the following:

test.ts:

import * as dbStuff from './db';

const mockGetData = jest.spyOn(dbStuff, "getFromDb").mockImplementation((y) => Promise.resolve({Item: []}));

Anything I have tried, my IDE tells me:

XYZ is not assignable to parameter of type Promise<GetItemCommandOutput>