Do I have to wait for promises to be resolved or does expect(...).toBe handle it automatically?

Question

Do I have to wait for promises to be resolved or does expect(...).toBe handle it automatically?

Testing with Protractor can be quite challenging and confusing, especially for those new to it.

I currently have the following setup:

`SomeTestFile.spec.ts`
describe('A test: ', () => {

    beforeEach(() => {
      ....
    }

    it ('Should validate a label', async() => {
      await helper.validateALabel(label);
    }   

    ....
}

In the helper class:

helper.ts
export class Helper {
  ....

  public validateLabel(label: String): Promise<void> {
    expect(label).toBe('This is the string of the label');
  }

  ....
}

My question is whether I need to await the expect(label).toBe(...)?

Should I use

await expect(label).toBe(...)

OR is it okay as it is (and if so, why do I keep receiving Unhandled Promise Rejection Warnings)?

expect(label).toBe(...)

angular typescript protractor

Answer 1

Answer №1

It does not.

You must wait for your promise to resolve and then compare the result.

// example promise function
const checkLabel = (label) => new Promise(r => r(true))

it ('validates a label', async () => {
  const isValid = await checkLabel(label)

  expect(isValid).toBeTruthy()
})

In this scenario, it appears that you are incorrectly specifying the return type:

public confirmLabel(label: String): Promise<void> {
  expect(label).toBe('This is the string of the label');
}

Here, it actually does not return a Promise<void>, but simply void, so there is no need for async/await at all.

Answer 2

It does not.

You must wait for your promise to resolve and then compare the result.

// example promise function
const checkLabel = (label) => new Promise(r => r(true))

it ('validates a label', async () => {
  const isValid = await checkLabel(label)

  expect(isValid).toBeTruthy()
})

In this scenario, it appears that you are incorrectly specifying the return type:

public confirmLabel(label: String): Promise<void> {
  expect(label).toBe('This is the string of the label');
}

Here, it actually does not return a Promise<void>, but simply void, so there is no need for async/await at all.

Answer 3

Answer №2

If you want:

test('returns as pineapple', async () => {
  await expect(Promise.resolve('pineapple')).resolves.toBe('pineapple');
});

Check out the details at https://jestjs.io/docs/en/expect#resolves

Answer 4

If you want:

test('returns as pineapple', async () => {
  await expect(Promise.resolve('pineapple')).resolves.toBe('pineapple');
});

Check out the details at https://jestjs.io/docs/en/expect#resolves

Answer 5

Answer №3

Utilizing expects in step definitions is a recommended practice. By retrieving the value from the helper class, you can include assertions in your step definitions to determine whether the test step passes or fails.

`AnotherTestFile.spec.ts`
describe('Testing functionality: ', () => {

    beforeEach(() => {
      ....
    }

    it ('Verifying a specific element', async() => {
      await expect(helper.validateAnElement(element)).toBe('This is the content of the element');
    }   

    ....
    }

helper.ts

export class Helper {
  ....
 function validateElement(element) {
    return new Promise((resolve, reject) => {
        return resolve('This is the content of the element');
    })
 }

  ....
}

Answer 6

Utilizing expects in step definitions is a recommended practice. By retrieving the value from the helper class, you can include assertions in your step definitions to determine whether the test step passes or fails.

`AnotherTestFile.spec.ts`
describe('Testing functionality: ', () => {

    beforeEach(() => {
      ....
    }

    it ('Verifying a specific element', async() => {
      await expect(helper.validateAnElement(element)).toBe('This is the content of the element');
    }   

    ....
    }

helper.ts

export class Helper {
  ....
 function validateElement(element) {
    return new Promise((resolve, reject) => {
        return resolve('This is the content of the element');
    })
 }

  ....
}

Do I have to wait for promises to be resolved or does expect(...).toBe handle it automatically?

Answer №1

Answer №2

Answer №3

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