playwright/docs/src/api/class-genericassertions.md

class: GenericAssertions

• since: v1.9
• langs: js

The [GenericAssertions] class provides assertion methods that can be used to make assertions about any values in the tests. A new instance of [GenericAssertions] is created by calling [method: PlaywrightAssertions.expectGeneric]:

import { test, expect } from '@playwright/test';

test('assert a value', async ({ page }) => {
  const value = 1;
  await expect(value).toBe(2);
});

property: GenericAssertions.not

• since: v1.9

• returns: <[GenericAssertions]>

Makes the assertion check for the opposite condition. For example, the following code passes:

const value = 1;
await expect(value).not.toBe(2);

method: GenericAssertions.toBe

• since: v1.9

Compares value with [param: expected] by calling Object.is. This method compares objects by reference instead of their contents, similarly to the strict equality operator ===.

Usage

const value = { prop: 1 };
expect(value).toBe(value);
expect(value).not.toBe({});
expect(value.prop).toBe(1);

param: GenericAssertions.toBe.expected

• since: v1.9

• expected <[any]>

Expected value.

method: GenericAssertions.toBeCloseTo

• since: v1.9

Compares floating point numbers for approximate equality. Use this method instead of [method: GenericAssertions.toBe] when comparing floating point numbers.

Usage

expect(0.1 + 0.2).not.toBe(0.3);
expect(0.1 + 0.2).toBeCloseTo(0.3, 5);

param: GenericAssertions.toBeCloseTo.expected

• since: v1.9

• expected <[float]>

Expected value.

param: GenericAssertions.toBeCloseTo.numDigits

• since: v1.9

• numDigits ?<[int]>

The number of decimal digits after the decimal point that must be equal.

method: GenericAssertions.toBeDefined

• since: v1.9

Ensures that value is not undefined.

Usage

const value = null;
expect(value).toBeDefined();

method: GenericAssertions.toBeFalsy

• since: v1.9

Ensures that value is false in a boolean context, one of false, 0, '', null, undefined or NaN. Use this method when you don't care about the specific value.

Usage

const value = null;
expect(value).toBeFalsy();

method: GenericAssertions.toBeGreaterThan

• since: v1.9

Ensures that value > expected for number or big integer values.

Usage

const value = 42;
expect(value).toBeGreaterThan(1);

param: GenericAssertions.toBeGreaterThan.expected

• since: v1.9

• expected <[float]|[bigint]>

The value to compare to.

method: GenericAssertions.toBeGreaterThanOrEqual

• since: v1.9

Ensures that value >= expected for number or big integer values.

Usage

const value = 42;
expect(value).toBeGreaterThanOrEqual(42);

param: GenericAssertions.toBeGreaterThanOrEqual.expected

• since: v1.9

• expected <[float]|[bigint]>

The value to compare to.

method: GenericAssertions.toBeInstanceOf

• since: v1.9

Ensures that value is an instance of a class. Uses instanceof operator.

Usage

expect(page).toBeInstanceOf(Page);

class Example {}
expect(new Example()).toBeInstanceOf(Example);

param: GenericAssertions.toBeInstanceOf.expected

• since: v1.9

• expected <[Function]>

The class or constructor function.

method: GenericAssertions.toBeLessThan

• since: v1.9

Ensures that value < expected for number or big integer values.

Usage

const value = 42;
expect(value).toBeLessThan(100);

param: GenericAssertions.toBeLessThan.expected

• since: v1.9

• expected <[float]|[bigint]>

The value to compare to.

method: GenericAssertions.toBeLessThanOrEqual

• since: v1.9

Ensures that value <= expected for number or big integer values.

Usage

const value = 42;
expect(value).toBeLessThanOrEqual(42);

param: GenericAssertions.toBeLessThanOrEqual.expected

• since: v1.9

• expected <[float]|[bigint]>

The value to compare to.

method: GenericAssertions.toBeNaN

• since: v1.9

Ensures that value is NaN.

Usage

const value = NaN;
expect(value).toBeNaN();

method: GenericAssertions.toBeNull

• since: v1.9

Ensures that value is null.

Usage

const value = null;
expect(value).toBeNull();

method: GenericAssertions.toBeTruthy

• since: v1.9

Ensures that value is true in a boolean context, anything but false, 0, '', null, undefined or NaN. Use this method when you don't care about the specific value.

Usage

const value = { example: 'value' };
expect(value).toBeTruthy();

method: GenericAssertions.toBeUndefined

• since: v1.9

Ensures that value is undefined.

Usage

const value = undefined;
expect(value).toBeUndefined();

method: GenericAssertions.toContain#1

• since: v1.9

Ensures that string value contains an expected substring. Comparison is case-sensitive.

Usage

const value = 'Hello, World';
expect(value).toContain('World');
expect(value).toContain(',');

param: GenericAssertions.toContain#1.expected

• since: v1.9

• expected <[string]>

Expected substring.

method: GenericAssertions.toContain#2

• since: v1.9

Ensures that value is an Array or Set and contains an expected item.

Usage

const value = [1, 2, 3];
expect(value).toContain(2);
expect(new Set(value)).toContain(2);

param: GenericAssertions.toContain#2.expected

• since: v1.9

• expected <[any]>

Expected value in the collection.

method: GenericAssertions.toContainEqual

• since: v1.9

Ensures that value is an Array or Set and contains an item equal to the expected.

For objects, this method recursively checks equality of all fields, rather than comparing objects by reference as performed by [method: GenericAssertions.toContain#2].

For primitive values, this method is equivalent to [method: GenericAssertions.toContain#2].

Usage

const value = [
  { example: 1 },
  { another: 2 },
  { more: 3 },
];
expect(value).toContainEqual({ another: 2 });
expect(new Set(value)).toContainEqual({ another: 2 });

param: GenericAssertions.toContainEqual.expected

• since: v1.9

• expected <[any]>

Expected value in the collection.

method: GenericAssertions.toEqual

• since: v1.9

Compares contents of the value with contents of [param: expected], performing "deep equality" check.

For objects, this method recursively checks equality of all fields, rather than comparing objects by reference as performed by [method: GenericAssertions.toBe].

For primitive values, this method is equivalent to [method: GenericAssertions.toBe].

Usage

const value = { prop: 1 };
expect(value).toEqual({ prop: 1 });

param: GenericAssertions.toEqual.expected

• since: v1.9

• expected <[any]>

Expected value.

method: GenericAssertions.toHaveLength

• since: v1.9

Ensures that value has a .length property equal to [param: expected]. Useful for arrays and strings.

Usage

expect('Hello, World').toHaveLength(12);
expect([1, 2, 3]).toHaveLength(3);

param: GenericAssertions.toHaveLength.expected

• since: v1.9

• expected <[int]>

Expected length.

method: GenericAssertions.toHaveProperty

• since: v1.9

Ensures that property at provided keyPath exists on the object and optionally checks that property is equal to the [param: expected]. Equality is checked recursively, similarly to [method: GenericAssertions.toEqual].

Usage

const value = {
  a: {
    b: [42],
  },
  c: true,
};
expect(value).toHaveProperty('a.b');
expect(value).toHaveProperty('a.b', [42]);
expect(value).toHaveProperty('a.b[0]', 42);
expect(value).toHaveProperty('c');
expect(value).toHaveProperty('c', true);

param: GenericAssertions.toHaveProperty.keyPath

• since: v1.9

• keyPath <[string]>

Path to the property. Use dot notation a.b to check nested properties and indexed a[2] notation to check nested array items.

param: GenericAssertions.toHaveProperty.expected

• since: v1.9

• expected ?<[any]>

Optional expected value to compare the property to.

method: GenericAssertions.toMatch

• since: v1.9

Ensures that string value matches a regular expression.

Usage

const value = 'Is 42 enough?';
expect(value).toMatch(/Is \d+ enough/);

param: GenericAssertions.toMatch.expected

• since: v1.9

• expected <[RegExp]|[string]>

Regular expression to match against.

method: GenericAssertions.toMatchObject

• since: v1.9

Compares contents of the value with contents of [param: expected], performing "deep equality" check. Allows extra properties to be present in the value, unlike [method: GenericAssertions.toEqual], so you can check just a subset of object properties.

When comparing arrays, the number of items must match, and each item is checked recursively.

Usage

const value = {
  a: 1,
  b: 2,
  c: true,
};
expect(value).toMatchObject({ a: 1, c: true });
expect(value).toMatchObject({ b: 2, c: true });

expect([{ a: 1, b: 2 }]).toMatchObject([{ a: 1 }]);

param: GenericAssertions.toMatchObject.expected

• since: v1.9

• expected <[Object]|[Array]>

The expected object value to match against.

method: GenericAssertions.toStrictEqual

• since: v1.9

Compares contents of the value with contents of [param: expected] and their types.

Differences from [method: GenericAssertions.toEqual]:

• Keys with undefined properties are checked. For example, { a: undefined, b: 2 } does not match { b: 2 }.
• Array sparseness is checked. For example, [, 1] does not match [undefined, 1].
• Object types are checked to be equal. For example, a class instance with fields a and b will not equal a literal object with fields a and b.

Usage

const value = { prop: 1 };
expect(value).toStrictEqual({ prop: 1 });

param: GenericAssertions.toStrictEqual.expected

• since: v1.9

• expected <[any]>

Expected value.

method: GenericAssertions.toThrow

• since: v1.9

Calls the function and ensures it throws an error.

Optionally compares the error with [param: expected]. Allowed expected values:

• Regular expression - error message should match the pattern.
• String - error message should include the substring.
• Error object - error message should be equal to the message property of the object.
• Error class - error object should be an instance of the class.

Usage

expect(() => {
  throw new Error('Something bad');
}).toThrow();

expect(() => {
  throw new Error('Something bad');
}).toThrow(/something/);

expect(() => {
  throw new Error('Something bad');
}).toThrow(Error);

param: GenericAssertions.toThrow.expected

• since: v1.9

• expected ?<[any]>

Expected error message or error object.

method: GenericAssertions.toThrowError

• since: v1.9

An alias for [method: GenericAssertions.toThrow].

Usage

expect(() => {
  throw new Error('Something bad');
}).toThrowError();

param: GenericAssertions.toThrowError.expected

• since: v1.9

• expected ?<[any]>

Expected error message or error object.