Learning Redux

Truthiness

In JavaScript there are various kinds of truthy/falsy values. For example, an empty value could be represented as undefined, null, or false. Jest offers various matchers for these cases:

• toBeNull: This matches only null
• toBeUndefined: This matches only undefined
• toBeDefined: This is the opposite of toBeUndefined (= .not.toBeUndefined)
• toBeTruthy: This matches anything that would be considered true in an if statement
• toBeFalsy: This matches anything that would be considered false in an if statement

For example, null will pass the check for the following matchers:

test('null', () => {  const n = null  expect(n).toBeNull()  expect(n).toBeDefined()  expect(n).not.toBeUndefined()  expect(n).not.toBeTruthy()  expect(n).toBeFalsy()}

On the ...