spec/predicates/property.spec.ts

import 'mocha';

import { given } from 'mocha-testdata';

import { ensure, isDefined, isGreaterThanOrEqualTo, isString, property, TinyType } from '../../src';
import { expect } from '../expect';

describe('predicates', () => {

    /** @test {property} */
    describe('::property', () => {

        /** @test {property} */
        describe('shifts the focus from the value itself to its property', () => {

            class Name extends TinyType {
                constructor(public readonly value: string) {
                    super();
                    ensure('Name', value,
                        isDefined(),
                        property('length', isDefined(), isGreaterThanOrEqualTo(3)),
                        isString(),
                    );
                }
            }

            /** @test {property} */
            it('ensures that the property meets the predicates', () => {
                expect(() => new Name('Jan')).to.not.throw();
            });

            given(
                undefined,
                null,
            ).
            it('complains when the value is undefined', (value: any) => {
                expect(() => new Name({ length: value } as any)).
                    to.throw(`Name should have a property "length" that is defined`);
            });

            given<any, string>(
                [undefined,             'Name should be defined'],
                [{ length: undefined }, 'Name should have a property "length" that is defined'],
                ['JM',                  'Name should have a property "length" that is either equal to 3 or is greater than 3'],
                [['J', 'a', 'n'],       'Name should be a string'],
            ).
            it('can be composed with other predicates', (value: any, expectedError: string) => {
                expect(() => new Name(value)).
                    to.throw(expectedError);
            });
        });
    });
});