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before.spec.ts
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before.spec.ts
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import {of} from 'rxjs';
import {marbles} from 'rxjs-marbles';
import {toArray} from 'rxjs/operators';
import {before} from './before';
describe('before', () => {
it('should never emit for an empty observable', marbles(m => {
m.expect(m.cold('|').pipe(before(() => true))).toBeObservable('|');
m.expect(m.cold('-').pipe(before(() => true))).toBeObservable('-');
}));
it('should never emit for a single value', marbles(m => {
m.expect(m.cold('a|').pipe(before(() => true))).toBeObservable('-|');
m.expect(m.cold('(a|)').pipe(before(() => true))).toBeObservable('|');
m.expect(m.cold('a').pipe(before(() => true))).toBeObservable('-');
}));
it('should never emit the last value', marbles(m => {
m.expect(m.cold('a-b-c-d|').pipe(before(() => true))).toBeObservable('--a-b-c|');
m.expect(m.cold('a-b-c-d').pipe(before(() => true))).toBeObservable('--a-b-c');
m.expect(m.cold('(abcd)').pipe(before(() => true))).toBeObservable('(abc)');
}));
it('should emit the value that came before', marbles(m => {
m.expect(m.cold('a-b-c-d|').pipe(before(v => v === 'c'))).toBeObservable('----b--|');
m.expect(m.cold('a-b-c-d').pipe(before(v => v === 'c'))).toBeObservable('----b');
}));
it('should never emit if always false', marbles(m => {
m.expect(m.cold('a-b-c-d|').pipe(before(() => false))).toBeObservable('-------|');
m.expect(m.cold('|').pipe(before(() => false))).toBeObservable('|');
m.expect(m.cold('').pipe(before(() => false))).toBeObservable('');
}));
it('should be passed next and previous values', async () => {
const called: Array<number[]> = [];
const values = await of(1, 2, 3, 4, 5).pipe(
before((...args: any[]) => {
called.push(args);
return true;
}),
toArray()
).toPromise();
expect(values).toEqual([1, 2, 3, 4]);
expect(called).toEqual([[2, 1], [3, 2], [4, 3], [5, 4]]);
});
});