expect()

Creates an assertion. Chain with matchers like .toBe(), .toEqual(), .toThrow() to verify values.

Syntax

testing

expect(value).matcher(expected)

Example

testing

expect(2 + 2).toBe(4);
expect({ a: 1 }).toEqual({ a: 1 });
expect([1, 2, 3]).toHaveLength(3);
expect("hello").toContain("ell");
expect(null).toBeNull();
expect(fn).toThrow("error message");