I want to test this function using jest. here is my code-

templeate.ts

export const generateSalamWelcome = async function (
      actionSource: IActionSource,
      actionDetails: IActionDetails
    ): Promise<IReplyTemplate[] | undefined> {
      try {
        const { pageId } = actionSource;
        const { actionExt } = actionDetails;
        const restaurantData = await getRestaurantQueriesMultiple(pageId, []);
        if (restaurantData) {
          const replyTemplates: IReplyTemplate[] = [];
          const { enOnly, bnOnly } = restaurantData;
          const mode = getMode(enOnly, bnOnly, actionExt || languageModes.EN);
          replyTemplates.push(
            generateTextTemplate(
              selectTextEnBn(mode, strings.salamWelcomeEn, strings.salamWelcomeBn)
            )
          );
          return replyTemplates;
        }
      } catch (err) {
        logger.error(err);
      }
    };

I want to mock getRestaurantQueriesMultiple, getMode and generateTextTemplate functions. How do I mock them properly to return some dummy result?

CodePudding user response：

You can make use of mockImplementation() in jest. With this you can spyOn() on a class method or a function in a file. For example in your case, let's consider a filename MyFile.ts in which you have exported the function getMode(). If your getMode() exists in the same file template.ts then dont consider file name as MyFile, instead go with template.ts. So, inside your it block you could do something like this,

const dummyResult = 'dummyData';

jest.spyOn(MyFile, 'getMode')
  .mockImplementation(() => {
    return Promise.resolve(dummyResult);
  })

Similarly you can do the same for getRestaurantQueriesMultiple() and generateTextTemplate(). But make sure you mock all these functions before you make a call to the actual function, which in your case is generateSalamWelcome()

You can read more about mockImplementation() here Jest Mock Implementation