Assertive.ts

A type-safe fluent assertion library

Assertive.ts - Core API / Assertion

Class: Assertion<T>

Base class for all assertions.

Type parameters

Name Description
T the type of the actual value

Table of contents

Constructors

Properties

Methods

Constructors

constructor

• new Assertion<T>(actual): Assertion<T>

Type parameters

Name
T

Parameters

Name Type
actual T

Returns

Assertion<T>

Defined in

packages/core/src/lib/Assertion.ts:56

Properties

actual

• Protected Readonly actual: T

Defined in

packages/core/src/lib/Assertion.ts:50

inverted

• Protected Readonly inverted: boolean

Defined in

packages/core/src/lib/Assertion.ts:52

not

• Readonly not: Assertion<T>

Defined in

packages/core/src/lib/Assertion.ts:54

Methods

asType

▸ asType<S, A>(typeFactory): A

Check first if the value is of some specific type, in which case returns an assertion instance for that specific type. The new assertion is built from a factory that should extend from the base Assertion class.

We provide some basic factories in TypeFactories. If you need some other factory for a custom assertion for instance, you can easily create one from a Factory reference and a predicate.

Type parameters

Name Type Description
S S the type of the factory’s value
A extends Assertion<S> the type of the assertion factory

Parameters

Name Type Description
typeFactory TypeFactory<S, A> a factory to assert the type and create an assertion

Returns

A

a more specific assertion based on the factory type

Example

expect(unknownValue)
  .asType(TypeFactories.STRING)
  .toStartWith("/api/");

expect(uuid)
  .asType({
    Factory: UUIDAssertion, // a custom UUID assertion
    predicate: (value): value is UUID => {
     return typeof value === "string" && UUID.PATTER.test(value);
    },
  })
  .isValid();

Defined in

packages/core/src/lib/Assertion.ts:552

execute

▸ execute(options): this

A convenience method to execute the assertion. The inversion logic for .not is already embedded in this method, so this should always be used in assertions to keep the negation system working

Parameters

Name Type Description
options ExecuteOptions the execution options for the assertion

Returns

this

the Assertion instance if no error was thrown

Defined in

packages/core/src/lib/Assertion.ts:84

normalized

▸ normalized(): this

A convenience method to normalize the assertion instance. If it was inverted with .not, it’ll return it back to the previous non-inverted state. Otherwise, it returns the same instance.

Returns

this

the normalized assertion instance

Defined in

packages/core/src/lib/Assertion.ts:70

proxyInverter

▸ proxyInverter(isInverted): undefined | (target: Assertion<T>, p: string | symbol, receiver: any) => any

Parameters

Name Type
isInverted boolean

Returns

undefined | (target: Assertion<T>, p: string | symbol, receiver: any) => any

Defined in

packages/core/src/lib/Assertion.ts:569

toBe

▸ toBe(expected): this

Another alias of .toBeSame(..) assertion.

Parameters

Name Type Description
expected T the value to compare for referential equality

Returns

this

the assertion instance

Example

const x = { a: 1 };
const y = x;

expect(x).toBe(x);
expect(x).toBe(y);

expect(x).not.toBe({ ...x });

Defined in

packages/core/src/lib/Assertion.ts:481

toBeEqual

▸ toBeEqual(expected): this

Check if the value is deep strict equal to another value.

Parameters

Name Type Description
expected T the value to compare for deep equality

Returns

this

the assertion instance

Example

expect(3 + 2).toBeEqual(5);
expect({ a: { b: 1 } }).toBeEqual({ a: { b: 1 } });
expect(today).toBeEqual(new Date(today.toISOString()));

Defined in

packages/core/src/lib/Assertion.ts:333

toBeFalsy

▸ toBeFalsy(): this

Check if the value is a falsy value. There are six falsy values in JavaScript: null, undefined, 0, "", false, NaN. Everything else is truthy.

Returns

this

the assertion instance

Example

expect(0).toBeFalsy();
expect("").toBeFalsy();

Defined in

packages/core/src/lib/Assertion.ts:273

toBeInstanceOf

▸ toBeInstanceOf(Expected): this

Check if the value is an instance of the provided constructor.

Parameters

Name Type Description
Expected Constructor<unknown> the constructor the value should be an instance

Returns

this

the assertion instance

Example

expect(pontiac).toBeInstanceOf(Car);

expect(today).toBeInstanceOf(Date);

Defined in

packages/core/src/lib/Assertion.ts:303

toBeNull

▸ toBeNull(): this

Check if the value is null.

Returns

this

the assertion instance

Example

expect(myNullValue).toBeNull();

Defined in

packages/core/src/lib/Assertion.ts:186

toBeOfType

▸ toBeOfType(expected): this

Checks if the value is of a specific data type. The supported data types are the same as the typeof operator, plus an additional array which allows desabiguation between object (which can also be an array).

Parameters

Name Type Description
expected DataType the expected data type

Returns

this

the assertion instance

Example

const arr = [1, 2, 3];

expect(arr).toBeOfType("array");
expect(arr[0]).toBeOfType("number");
expect(arr[9]).toBeOfType("undefined");

Defined in

packages/core/src/lib/Assertion.ts:502

toBePresent

▸ toBePresent(): this

Check if the value is present. This means that the value should not be undefined.

Returns

this

the assertion instance

Example

expect(PI).toBePresent();

Defined in

packages/core/src/lib/Assertion.ts:214

toBeSame

▸ toBeSame(expected): this

Check if the value is the same as another value.

Parameters

Name Type Description
expected T the value to compare for referential equality

Returns

this

the assertion instance

Example

const x = { a: 1 };
const y = x;

expect(x).toBeSame(x);
expect(x).toBeSame(y);

expect(x).not.toBeSame({ ...x });

Defined in

packages/core/src/lib/Assertion.ts:425

toBeSameAs

▸ toBeSameAs(expected): this

Alias of .toBeSame(..) assertion.

Parameters

Name Type Description
expected T the value to compare for referential equality

Returns

this

the assertion instance

Example

const x = { a: 1 };
const y = x;

expect(x).toBeSameAs(x);
expect(x).toBeSameAs(y);

expect(x).not.toBeSameAs({ ...x });

Defined in

packages/core/src/lib/Assertion.ts:460

toBeSimilar

▸ toBeSimilar(expected): this

Check if the value is shallow equal to another value.

Parameters

Name Type Description
expected T the value to compare for shallow equality

Returns

this

the assertion instance

Example

expect(3 + 2).toBeSimilar(5);
expect({ a: 1 }).toBeSimilar({ a: 1 });

expect({ a: { b: 1 } }).not.toBeSimilar({ a: {b: 1} });

Defined in

packages/core/src/lib/Assertion.ts:365

toBeTruthy

▸ toBeTruthy(): this

Check if the value is a truthy value. There are six falsy values in JavaScript: null, undefined, 0, "", false, NaN. Everything else is truthy.

Returns

this

the assertion instance

Example

expect("hello world").toBeTruthy();
expect(128).toBeTruthy();

Defined in

packages/core/src/lib/Assertion.ts:244

toBeUndefined

▸ toBeUndefined(): this

Check if the value is undefined

Returns

this

the assertion instance

Example

expect(myUndefinedValue).toBeUndefined()

Defined in

packages/core/src/lib/Assertion.ts:159

toExist

▸ toExist(): this

Check if the value exists. This means that the value should be neither null nor undefined.

Returns

this

the assertion instance

Example

expect(planetEarth).toExist();

Defined in

packages/core/src/lib/Assertion.ts:132

toMatch

▸ toMatch(matcher): this

Check if the value matches the given predicate.

Parameters

Name Type Description
matcher (actual: T) => boolean a matcher predicate

Returns

this

the assertion instance

Defined in

packages/core/src/lib/Assertion.ts:104