@reactivex/rxjs/spec-dtslint/operators/count-spec.ts

Reactive Extensions for modern JavaScript

import { of, Observable } from 'rxjs';
import { count, buffer } from 'rxjs/operators';

it('should always infer number', () => {
  const o = of(1, 2, 3).pipe(count(x => x > 1)); // $ExpectType Observable<number>
  const j = of('a', 'b', 'c').pipe(count(x => x === 'a')); // $ExpectType Observable<number>
});

it('should accept empty parameter', () => {
  const o = of(1, 2, 3).pipe(count()); // $ExpectType Observable<number>
});

it('should infer source observable type in parameter', () => {
  const o = of(1, 2, 3).pipe(count((x, i, source: Observable<string>) => x === 3)); // $ExpectError
});

it('should enforce value type of source type', () => {
  const o = of(1, 2, 3).pipe(count((x, i, source) => x === '3')); // $ExpectError
});

it('should enforce index type of number', () => {
  const o = of(1, 2, 3).pipe(count((x, i, source) => i === '3')); // $ExpectError
});

it('should expect function parameter', () => {
  const o = of(1, 2, 3).pipe(count(9)); // $ExpectError
});

it('should enforce source type', () => {
  const o = of(1, 2, 3).pipe(count(x => x === '')); // $ExpectError
});