Jest | Fresco Play

Question 1: The below test will pass.

Answer: False

Question 2: .mock is a property of mock function, the place where all information about how the function has been called is kept.

Answer: True

Question 3: The Asynchronous code will move on to another task before it finishes.

Answer: True

Question 4: Jest will wait until the ______________ callback is called before finishing the test.

Answer: done

Question 5: ______________ resets all information stored in the mock, including any inital implementation given.

Answer: mockReset()

Question 6: To test a particular function which throws an error when it's called, you can use toThrow.

Answer: True

Question 7: Code coverage tests that how much code is covered under tests

Answer: True

Question 8: ______________ is useful when you want to completely restore a mock back to its initial state.

Answer: mockReset()

Question 9: ______________ returns the value only once when mock function is called.

Answer: mockReturnValueOnce(value)

Question 10: How to install Jest using yarn?

Answer: yarn add --dev jest

Question 11: Which method is useful to clean up a mock's usage data between two assertions.

Answer: mockClear()

Question 12: mockRestore() removes the mock and restores the initial implementation

Answer: True

Question 13: Jest is maintained by ______________ .

Answer: Facebook

Question 14: Jest records all calls that have been made during mock function and it is stored in ______________ array.

Answer: mock.calls

Question 15: Jest is used by ______________.

Answer: All of these

Question 16: Snapshot Testing is not supported in Jest.

Answer: False

Question 17: How to run your test in terminal?

Answer: npm test

Question 18: Function's actual implementations can be mocked in test using ____________.

Answer: Both

Question 19: ______________ recursively checks every field of an object or array.

Answer: toEqual

Question 20: The matcher toContain is used _________.

Answer: To check if an array contains a particular item

Question 21: Jest works well with other testing libraries like

Answer: all the options

Question 22: Jest is used to test _.

Answer: Java script

Question 23: Jest is a JavaScript unit testing framework.

Answer: True

Question 24: How to install Jest using npm?

Answer: npm install --save-dev jest

Question 25: You can check strings against regular expressions with ______________ .

Answer: toMatch

Question 26: Jest uses ________ and ________ matchers to test a value is with exact equality

Answer: ToBe , toEqual

Question 27: The number can be compared using

Answer: All the options

Question 28: To create a mock function, we use jest.fn().

Answer: True

Question 29: ______________ resets all information stored in the mockFn.mock.calls and mockFn.mock.instances arrays.

Answer: mockClear()

Question 30: Jest supports ______________ for Isolating functionality into small, testable units under test.

Answer: Mock Functions

Question 31: When you execute ______________ Code, it will move on to another task before it finishes.

Answer: Asynchronous

Question 32: ______________ is useful when you want to mock functions in certain test cases and restore the original implementation in others.

Answer: mockRestore()

Question 33: The Synchronous Code will move on to another task before it finishes.

Answer: False

Question 34: What is the command to install Jest and the babel-jest ?

Answer: $ npm install --save-dev jest babel-jest

Question 35: ______________ is an array that records all the object instances that have been instantiated from the mock function using new.

Answer: mock.instances

Question 36: ______________ matcher matches only undefined.

Answer: toBeUndefined

Question 37: mockRestore() works only when mock was created with ______________.

Answer: jest.spyOn

Question 38: For Code Coverage Support Jest requires some additional setup and libraries .

Answer: False

Question 39: If you expect a promise to be rejected, use the ______________ matcher. If the promise is fulfilled, the test will automatically fail.

Answer: .rejects

Question 40: Snapshot testing is a useful feature if you want to make sure your UI does not change unexpectedly.

Answer: True

Question 41: Predict the output of the test.

Answer: a b a