Mastering React Test-Driven Development

Extracting an expectation group function

The three expectations in this test will be needed every time we define a new text field. A simple way to avoid repeating each expectation is to extract an arrow function that runs all three as a group:

const expectToBeInputFieldOfTypeText = formElement => {  expect(formElement).not.toBeNull();  expect(formElement.tagName).toEqual('INPUT');  expect(formElement.type).toEqual('text');};

Define this function above your test and replace the expectations in your test with a call to this function.

In the next chapter, we'll build a Jest matcher that performs a similar function, but for a different use case.