Matchers in Jest

What are Matchers?

Matchers let you test values in different ways. In this block of code, the matcher is .toBe(3):

test("Adds 1 + 2 to equal 3", () => {
  expect(sum(1, 2)).toBe(3);
});

What do Matchers do?

Matchers are methods to let you validate different things about values. They are used to test the output of a function to determine in a function is working correctly.

Types of Matchers

• toBe( ) - used to test the exact equality of a number, string or boolean.
• toEqual( ) - used when comparing the values of objects or arrays
• toBeFalsy( ) - used to test if a value is false, 0, -0, "", null,undefined, or NaN.
• toBeTruthy( ) - used to match anything an if statement treats as true.
• toThrow( ) - used to test whether a function throws an error.