test example

postData.js

const writeToS3 = (data) => {
    console.info('writing to S3');
    fetch('s3Url', {
        method: 'POST',
        body: JSON.stringify(data),
        headers: {
        'Content-Type': 'application/json',
        }
    })
}


const postDataSomewhere = (data) => {
    writeToS3(moreData); // spy successfully
    fetch(data.url, {
        method: 'POST',
        body: JSON.stringify(data.body),
        headers: {
            'Content-Type': 'application/json',
        }
    }).then((moreData) => {
        writeToS3(moreData); // cannot spy on this
    })
}

/** Jasmine Tests Jasmine 3.4.0 */

describe('tests', () => {
    beforeEach(() => {
        s3spy = spyOn(writeToS3).and.callFake(function() {
            console.info("DELEGATED TO SPY ON WRITETOS3")
        });
    })
    
    it('should call things with correct stuff', (done) => {
        postDataSomewhere()
        expect(s3spy).toHaveBeenCalledTimes(2)
        done();
    })
})