Hein

Assertion library with focus on TypeScript

Features

• Full TypeScript support

• Fuzzy matching for eql with hein.any

• Differences between Chai and Hein

Plugins

npm/hein-plugin-sinon - Provides assertions like to.have.been.calledOnce() and to.have.been.calledWith() for sinon spies.

Usage

Assert

import { assert } from 'hein';
import { equal } from 'hein/assert';

equal(1, 1);
assert.equal(1, 1);
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Expect

import { expect } from 'hein';
expect(1).to.equal(1);
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Chainable properties

Language chains

There are multiple side-effect free tokens to chain assertions together. These include:

• to
• be
• a
• an
• have
• in
• of

expect(5).to.be.a.number(); // same as expect(5).number();
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not

Not inverts the conditions inside the expectation.

expect(5).to.not.equal(4);
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every

Run the assertion for each member of an array

expect([1, 2, 3]).every.to.be.a.number();
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length

Run the assertion on the length of an array

expect([1, 2, 3]).length.to.be.greaterThan(2);
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and

Clears most of the state in the chain (with the exception of the effects of .every);

expect(1).to.not.be.greaterThan(5).and.be.greaterThan(0);
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Assertions

above

Alias for greaterThan

array

Assert that value is an array

expect([]).to.be.an.array();
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atLeast

Alias for greaterThanOrEqual

atMost

Alias for lessThanOrEqual

ballpark

Assert that value is within a range of expectation (default is 0.1 - within 10%)

expect(1.1).to.be.in.ballpark(1);
expect(120).to.be.in.ballpark(100, 0.2);
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below

Alias for lessThan

bigint

Assert that value is a BigInt

expect(BigInt(5)).to.be.a.bigint();
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boolean

Assert that value is a boolean

expect(true).to.be.a.boolean();
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contain

Alias for include

Date

Assert that value is an instance of Date

expect(new Date()).to.be.a.date();
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empty

Assert that array / object / Map / Set is empty

expect([]).to.be.empty();
expect({}).to.be.empty();
expect(new Map()).to.be.empty();
expect(new Set()).to.be.empty();
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endWith

Assert that string ends with argument

expect('hein').to.endWith('in');
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eql

Assert that value deep equals the expectation. When combined with .partially expected may have missing properties

expect({ a: 1 }).to.eql({ a: 1 });
expect({ a: 1, b: new Date() }).to.partially.eql({ a: 1 });

import { any, createEvaluation } from 'hein';
expect({ a: 1, b: new Date(), c: Math.random() }).to.eql({
    a: 1,
    b: any,
    c: createEvaluation((n) => typeof n === 'number')
});
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eq

Alias for equal

equal

Assert that value strictly equals expectation. NaN is treated as a non-unique value. Chaining with .deep is an alias for [#eql]

expect('hein').to.equal('hein');
expect(NaN).to.equal(NaN);
expect({ a: 1 }).to.deep.equal({ a: 1 });
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false

Assert that value is false

expect(false).to.be.false();
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function

Assert that value is a function

expect(() => {}).to.be.a.function();
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greaterThan

Assert that value is greater than expectation

expect(5).to.be.greaterThan(4);
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gt

Alias for greaterThan

greaterThanOrEqual

Assert that value is greater than or equal to argument

expect(5).to.be.greaterThanOrEqual(5);
expect(5).to.be.greaterThanOrEqual(4);
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gte

Alias for greaterThanOrEqual

include

Assert that element / substring is present in array / string

expect([1, 2, 3]).to.include(2);
expect('hein').to.include('ei');
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instanceOf

Assert that value is an instance of provided constructor

expect(new Error()).to.be.an.instanceOf(Error);
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keys

Assert that object has keys

expect({ a: 1, b: 2 }).to.have.keys(['a', 'b']);
expect({ a: 1, b: 2 }).to.have.keys('a');
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lengthOf

Assert that value has a length equal to argument

expect([1]).to.have.a.lengthOf(1);
expect({ a: 1 }).to.have.a.lengthOf(1);
expect(new Map([['a', 1]])).to.have.a.lengthOf(1);
expect(new Set([1])).to.have.a.lengthOf(1);
expect('hein').to.have.a.lengthOf(4);
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isAfter

Assert that date is before argument

expect(new Date(2020, 1, 2)).to.be.after(new Date(2020, 1, 1));
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isBefore

Assert that date is before argument

expect(new Date(2020, 1, 1)).to.be.before(new Date(2020, 1, 2));
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isBetween

Assert that date or number is between arguments

expect(new Date(2020, 1, 2)).to.be.between(new Date(2020, 1, 1), new Date(2020, 1, 3));
expect(2).to.be.between(1, 3);
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lessThan

Assert that value is less than expectation

expect(5).to.be.lessThan(6);
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lt

Alias for lessThan

lessThanOrEqual

Assert that value is less than or equal to expectation

expect(5).to.be.lessThanOrEqual(5);
expect(4).to.be.lessThanOrEqual(5);
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lte

Alias for lessThanOrEqual

Map

Assert that value is an instance of Map

expect(new Map()).to.be.a.Map();
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members

Assert that array contains members of expectation

expect([1, 2, 3]).to.have.members([1, 2]);
// check that the arrays have same length
expect([1, 2, 3]).to.have.same.members([1, 2, 3]);
// check that the members are found in the same order
expect([1, 2, 3]).to.have.ordered.members([1, 2, 3]);
// check for deep equality of members
expect([{ a: 1 }, { b: 2 }]).to.have.deep.members([{ a: 1 }]);
// check for members by partial equality
expect([{ a: 1 }, { b: 2 }]).to.have.partially.members([{ a: 1 }]);
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NaN

Assert that value is NaN

expect(NaN).to.be.NaN();
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null

Assert that value is null

expect(null).to.be.null();
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number

Assert that value is a number

expect(5).to.be.a.number();
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object

Assert that value is an object. Null and instances of Array don't count

expect({}).to.be.an.object();
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property

Assert that actual has property. Optionally check that propery has value

expect({ a: 1 }).to.have.property('a');
expect({ a: 1 }).to.have.property('a', 1);
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reject

Assert that provided Promise rejects. At the moment this is the only assertion that can't be chained, returns a promise

await expect(Promise.reject()).to.reject();
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roundTo

Assert that number can be rounded to target

expect(5.5).to.be.roundTo(6);
expect(5.14).to.roundTo(5.1, 1);
expect(110).to.roundTo(100, -2);
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Set

Assert that value is an instance of Set

expect(new Set()).to.be.a.Set();
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sizeOf

Alias of lengthOf

startWith

Assert that string starts with argument

expect('hein').to.startWith('he');
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string

Assert that value is a string

expect('hein').to.be.a.string();
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symbol

Assert that value is a symbol

expect(Symbol()).to.be.a.symbol();
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throw

Assert that provided function throws

expect(() => {
    throw new Error();
}).to.throw();
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true

Assert that value is true

expect(true).to.be.true;
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undefined

Assert that value is undefined

expect(undefined).to.be.undefined();
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WeakMap

Assert that value is an instance of WeakMap

expect(new WeakMap()).to.be.a.WeakMap();
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WeakSet

Assert that value is an instance of WeakSet

expect(new WeakSet()).to.be.a.WeakSet();
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Modifiers

excluding

Exclude properties from assertion

expect({ a: 1, b: 2 }).excluding('a').to.eql({ b: 2 });
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