Oli Sturm
83 lines
2.0 KiB
JavaScript
83 lines
2.0 KiB
JavaScript
import { describe, it, expect, vi } from 'vitest';
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import { match, when, any } from '../js-fp3/library/patterns.js';
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describe('when', () => {
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it('returns a two-element tuple of [predicate, handler]', () => {
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const predicate = () => true;
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const handler = () => 'result';
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const branch = when(predicate, handler);
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expect(branch).toEqual([predicate, handler]);
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});
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});
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describe('any', () => {
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it('returns true for any value', () => {
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expect(any(0)).toBe(true);
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expect(any(null)).toBe(true);
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expect(any('string')).toBe(true);
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expect(any({ x: 1 })).toBe(true);
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});
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});
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describe('match', () => {
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it('executes the handler of the first matching branch', () => {
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const result = match(
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when((v) => v === 1, () => 'one'),
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when((v) => v === 2, () => 'two'),
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when(any, () => 'other')
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)(1);
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expect(result).toBe('one');
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});
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it('falls through to the next branch when the first does not match', () => {
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const result = match(
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when((v) => v === 1, () => 'one'),
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when((v) => v === 2, () => 'two'),
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when(any, () => 'other')
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)(2);
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expect(result).toBe('two');
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});
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it('uses the any catch-all when no earlier branch matches', () => {
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const result = match(
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when((v) => v === 1, () => 'one'),
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when(any, () => 'catch-all')
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)(99);
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expect(result).toBe('catch-all');
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});
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it('passes the value to the handler', () => {
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const result = match(
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when(any, (v) => v * 2)
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)(7);
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expect(result).toBe(14);
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});
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it('throws when no branch matches', () => {
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expect(() =>
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match(
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when((v) => v === 1, () => 'one')
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)(99)
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).toThrow('No matching pattern');
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});
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it('does not call handlers for branches that were not selected', () => {
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const skipped = vi.fn(() => 'skipped');
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const selected = vi.fn(() => 'selected');
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match(
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when((v) => v === 1, selected),
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when(any, skipped)
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)(1);
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expect(selected).toHaveBeenCalledOnce();
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expect(skipped).not.toHaveBeenCalled();
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});
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});
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