esm-logging/tests/unit/handler.test.ts

import {expect, jest, test} from '@jest/globals';
import {
    Handler,
    StreamHandler,
    ConsoleHandler,
    StderrHandler,
    FileHandler,
} from '../../src/handler';
import { Formatter, DEFAULT_FORMATTER } from '../../src/formatter';
import { LogRecord } from '../../src/log-record';
import { Writable } from '../../src/helper/stream';
import { DEBUG, INFO, WARNING, ERROR, CRITICAL, NOTSET } from '../../src/log-level';

function makeRecord(level: number, msg: string): LogRecord {
    return new LogRecord('test', { level, msg });
}

describe('Handler', () => {
    describe('constructor', () => {
        test('defaults to NOTSET level', () => {
            const h = new Handler();
            expect(h.level).toBe(NOTSET);
        });

        test('accepts a level argument', () => {
            const h = new Handler(WARNING);
            expect(h.level).toBe(WARNING);
        });
    });

    describe('level setter', () => {
        test('sets the level without infinite recursion', () => {
            const h = new Handler();
            h.level = ERROR;
            expect(h.level).toBe(ERROR);
        });
    });

    describe('formatter', () => {
        test('getter returns null when no formatter set', () => {
            const h = new Handler();
            expect(h.formatter).toBeNull();
        });

        test('getter returns assigned formatter', () => {
            const h = new Handler();
            const fmt = new Formatter();
            h.formatter = fmt;
            expect(h.formatter).toBe(fmt);
        });
    });

    describe('format', () => {
        test('uses DEFAULT_FORMATTER when no formatter assigned', () => {
            const h = new Handler();
            const record = makeRecord(DEBUG, 'hello');
            const result = h.format(record);
            expect(typeof result).toBe('string');
        });

        test('returns a string', () => {
            const h = new Handler();
            const record = makeRecord(WARNING, 'test message');
            expect(typeof h.format(record)).toBe('string');
        });
    });

    describe('emit', () => {
        test('throws NotImplementedError on base class', () => {
            const h = new Handler();
            const record = makeRecord(DEBUG, 'hello');
            expect(() => h.emit(record)).toThrow('emit must be implemented');
        });
    });

    describe('close', () => {
        test('sets closed to true', () => {
            const h = new Handler();
            expect(h.closed).toBe(false);
            h.close();
            expect(h.closed).toBe(true);
        });
    });

    describe('handleError', () => {
        test('does not throw', () => {
            const h = new Handler();
            const record = makeRecord(DEBUG, 'test');
            expect(() => h.handleError(record)).not.toThrow();
        });
    });
});

describe('StreamHandler', () => {
    test('writes formatted output to the stream', () => {
        const written: string[] = [];
        const stream: Writable = { write: (data: string) => { written.push(data) } };
        const h = new StreamHandler(stream);
        const record = makeRecord(WARNING, 'stream test');
        h.emit(record);
        expect(written.length).toBe(1);
        expect(written[0]).toContain('stream test');
    });

    test('uses default stream when none provided', () => {
        const h = new StreamHandler();
        const record = makeRecord(DEBUG, 'default stream');
        expect(() => h.emit(record)).not.toThrow();
    });

    test('calls handleError on emit failure', () => {
        const stream: Writable = {
            write: () => { throw new Error('write failed') }
        };
        const h = new StreamHandler(stream);
        const record = makeRecord(DEBUG, 'fail');
        expect(() => h.emit(record)).not.toThrow();
    });
});

describe('ConsoleHandler', () => {
    let origLog: typeof console.log;
    let origWarn: typeof console.warn;
    let origError: typeof console.error;
    let logged: string[];
    let warned: string[];
    let errored: string[];

    beforeEach(() => {
        logged = [];
        warned = [];
        errored = [];
        origLog = console.log;
        origWarn = console.warn;
        origError = console.error;
        console.log = (...args: any[]) => { logged.push(args.join(' ')) };
        console.warn = (...args: any[]) => { warned.push(args.join(' ')) };
        console.error = (...args: any[]) => { errored.push(args.join(' ')) };
    });

    afterEach(() => {
        console.log = origLog;
        console.warn = origWarn;
        console.error = origError;
    });

    test('uses console.error for ERROR level', () => {
        const h = new ConsoleHandler();
        h.emit(makeRecord(ERROR, 'error msg'));
        expect(errored.length).toBe(1);
        expect(errored[0]).toContain('error msg');
    });

    test('uses console.error for CRITICAL level', () => {
        const h = new ConsoleHandler();
        h.emit(makeRecord(CRITICAL, 'critical msg'));
        expect(errored.length).toBe(1);
        expect(errored[0]).toContain('critical msg');
    });

    test('uses console.warn for WARNING level', () => {
        const h = new ConsoleHandler();
        h.emit(makeRecord(WARNING, 'warn msg'));
        expect(warned.length).toBe(1);
        expect(warned[0]).toContain('warn msg');
    });

    test('uses console.log for INFO level', () => {
        const h = new ConsoleHandler();
        h.emit(makeRecord(INFO, 'info msg'));
        expect(logged.length).toBe(1);
        expect(logged[0]).toContain('info msg');
    });

    test('uses console.log for DEBUG level', () => {
        const h = new ConsoleHandler();
        h.emit(makeRecord(DEBUG, 'debug msg'));
        expect(logged.length).toBe(1);
        expect(logged[0]).toContain('debug msg');
    });
});

describe('StderrHandler', () => {
    test('accepts a level', () => {
        const h = new StderrHandler(ERROR);
        expect(h.level).toBe(ERROR);
    });

    test('emits via console.error', () => {
        const errored: string[] = [];
        const origError = console.error;
        console.error = (...args: any[]) => { errored.push(args.join(' ')) };
        try {
            const h = new StderrHandler(DEBUG);
            h.emit(makeRecord(WARNING, 'stderr test'));
            expect(errored.length).toBe(1);
            expect(errored[0]).toContain('stderr test');
        }
        finally {
            console.error = origError;
        }
    });
});

describe('FileHandler', () => {
    test('throws NotImplementedError on construction', () => {
        expect(() => new FileHandler({
            filename: 'test.log'
        })).toThrow('not available in browser');
    });
});