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;
expect(value).toBe(2);
});
property: GenericAssertions.not
- since: v1.9
- returns: <[GenericAssertions]>
Makes the assertion check for the opposite condition.
Usage
For example, the following code passes:
const value = 1;
expect(value).not.toBe(2);
property: GenericAssertions.resolves
- since: v1.9
- returns: <[GenericAssertions]>
Use resolves to unwrap the value of a fulfilled promise so any other matcher can be chained. If the promise is rejected the assertion fails.
For example, this code tests that the promise resolves and that the resulting value is 'lemon':
test('resolves to lemon', async () => {
await expect(Promise.resolve('lemon')).resolves.toBe('lemon');
});
property: GenericAssertions.rejects
- since: v1.9
- returns: <[GenericAssertions]>
Use .rejects to unwrap the reason of a rejected promise so any other matcher can be chained. If the promise is fulfilled the assertion fails.
For example, this code tests that the promise rejects with reason 'octopus':
test('rejects to octopus', async () => {
await expect(Promise.reject(new Error('octopus'))).rejects.toThrow('octopus');
});
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 });
Non-strict equality
[method: GenericAssertions.toEqual] performs deep equality check that compares contents of the received and expected values. To ensure two objects reference the same instance, use [method: GenericAssertions.toBe] instead.
[method: GenericAssertions.toEqual] ignores undefined properties and array items, and does not insist on object types being equal. For stricter matching, use [method: GenericAssertions.toStrictEqual].
Pattern matching
[method: GenericAssertions.toEqual] can be also used to perform pattern matching on objects, arrays and primitive types, with the help of the following matchers:
- [
method: GenericAssertions.any] - [
method: GenericAssertions.anything] - [
method: GenericAssertions.arrayContaining] - [
method: GenericAssertions.arrayOf] - [
method: GenericAssertions.closeTo] - [
method: GenericAssertions.objectContaining] - [
method: GenericAssertions.stringContaining] - [
method: GenericAssertions.stringMatching]
Here is an example that asserts some of the values inside a complex object:
expect({
list: [1, 2, 3],
obj: { prop: 'Hello world!', another: 'some other value' },
extra: 'extra',
}).toEqual(expect.objectContaining({
list: expect.arrayContaining([2, 3]),
obj: expect.objectContaining({ prop: expect.stringContaining('Hello') }),
}));
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
aandbwill not equal a literal object with fieldsaandb.
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.
method: GenericAssertions.any
- since: v1.9
expect.any() matches any object instance created from the [param: constructor] or a corresponding primitive type. Use it inside [method: GenericAssertions.toEqual] to perform pattern matching.
Usage
// Match instance of a class.
class Example {}
expect(new Example()).toEqual(expect.any(Example));
// Match any number.
expect({ prop: 1 }).toEqual({ prop: expect.any(Number) });
// Match any string.
expect('abc').toEqual(expect.any(String));
param: GenericAssertions.any.constructor
- since: v1.9
constructor<[Function]>
Constructor of the expected object like ExampleClass, or a primitive boxed type like Number.
method: GenericAssertions.anything
- since: v1.9
expect.anything() matches everything except null and undefined. Use it inside [method: GenericAssertions.toEqual] to perform pattern matching.
Usage
const value = { prop: 1 };
expect(value).toEqual({ prop: expect.anything() });
expect(value).not.toEqual({ otherProp: expect.anything() });
method: GenericAssertions.arrayContaining
- since: v1.9
expect.arrayContaining() matches an array that contains all of the elements in the expected array, in any order. Note that received array may be a superset of the expected array and contain some extra elements.
Use this method inside [method: GenericAssertions.toEqual] to perform pattern matching.
Usage
expect([1, 2, 3]).toEqual(expect.arrayContaining([3, 1]));
expect([1, 2, 3]).not.toEqual(expect.arrayContaining([1, 4]));
param: GenericAssertions.arrayContaining.expected
- since: v1.9
expected<[Array]<[any]>>
Expected array that is a subset of the received value.
method: GenericAssertions.arrayOf
- since: v1.57
expect.arrayOf() matches array of objects created from the [param: constructor] or a corresponding primitive type. Use it inside [method: GenericAssertions.toEqual] to perform pattern matching.
Usage
// Match instance of a class.
class Example {}
expect([new Example(), new Example()]).toEqual(expect.arrayOf(Example));
// Match any string.
expect(['a', 'b', 'c']).toEqual(expect.arrayOf(String));
param: GenericAssertions.arrayOf.constructor
- since: v1.57
constructor<[Function]>
Constructor of the expected object like ExampleClass, or a primitive boxed type like Number.
method: GenericAssertions.closeTo
- since: v1.9
Compares floating point numbers for approximate equality. Use this method inside [method: GenericAssertions.toEqual] to perform pattern matching. When just comparing two numbers, prefer [method: GenericAssertions.toBeCloseTo].
Usage
expect({ prop: 0.1 + 0.2 }).not.toEqual({ prop: 0.3 });
expect({ prop: 0.1 + 0.2 }).toEqual({ prop: expect.closeTo(0.3, 5) });
param: GenericAssertions.closeTo.expected
- since: v1.9
expected<[float]>
Expected value.
param: GenericAssertions.closeTo.numDigits
- since: v1.9
numDigits?<[int]>
The number of decimal digits after the decimal point that must be equal.
method: GenericAssertions.objectContaining
- since: v1.9
expect.objectContaining() matches an object that contains and matches all of the properties in the expected object. Note that received object may be a superset of the expected object and contain some extra properties.
Use this method inside [method: GenericAssertions.toEqual] to perform pattern matching. Object properties can be matchers to further relax the expectation. See examples.
Usage
// Assert some of the properties.
expect({ foo: 1, bar: 2 }).toEqual(expect.objectContaining({ foo: 1 }));
// Matchers can be used on the properties as well.
expect({ foo: 1, bar: 2 }).toEqual(expect.objectContaining({ bar: expect.any(Number) }));
// Complex matching of sub-properties.
expect({
list: [1, 2, 3],
obj: { prop: 'Hello world!', another: 'some other value' },
extra: 'extra',
}).toEqual(expect.objectContaining({
list: expect.arrayContaining([2, 3]),
obj: expect.objectContaining({ prop: expect.stringContaining('Hello') }),
}));
param: GenericAssertions.objectContaining.expected
- since: v1.9
expected<[Object]>
Expected object pattern that contains a subset of the properties.
method: GenericAssertions.stringContaining
- since: v1.9
expect.stringContaining() matches a string that contains the expected substring. Use this method inside [method: GenericAssertions.toEqual] to perform pattern matching.
Usage
expect('Hello world!').toEqual(expect.stringContaining('Hello'));
param: GenericAssertions.stringContaining.expected
- since: v1.9
expected<[string]>
Expected substring.
method: GenericAssertions.stringMatching
- since: v1.9
expect.stringMatching() matches a received string that in turn matches the expected pattern. Use this method inside [method: GenericAssertions.toEqual] to perform pattern matching.
Usage
expect('123ms').toEqual(expect.stringMatching(/\d+m?s/));
// Inside another matcher.
expect({
status: 'passed',
time: '123ms',
}).toEqual({
status: expect.stringMatching(/passed|failed/),
time: expect.stringMatching(/\d+m?s/),
});
param: GenericAssertions.stringMatching.expected
- since: v1.9
expected<[string]|[RegExp]>
Pattern that expected string should match.
Source: docs/src/api/class-genericassertions.md