Merv-Logs — live console & MervLogger

Introduction

Merv-Logs is a live log viewer for Merv-Local runs. Call MervLogger from Java (merv-client-api) or JavaScript / TypeScript (merv-client). Lines go to the console (optional) and to {reportRoot}/log/ as rolling NDJSON. Open Merv-Logs from the dashboard to filter, search, and scroll history.

Quick start

import org.teche.merv.client.logging.MervLogger;
import org.teche.merv.client.logging.MervLoggerFactory;

MervLogger log = MervLoggerFactory.getLogger(MyClass.class);
log.info("Starting checks");
log.debug("Detail only when level is DEBUG");
log.warn("Retrying request…");
log.info("Cart total={}", 42);

npm install merv-client
npx merv-client doctor setup-log

import { MervLogger, console } from 'merv-client';

MervLogger.info('Starting checks');
console.log('Also mirrors to Merv-Logs');
MervLogger.debug('Detail only when level is DEBUG');
MervLogger.warn('Retrying request…');

const log = MervLogger.getLogger('Checkout');
log.info('Cart total={}', 42);

node my-check.js
npx merv show-logs

Doctor commands (JS/TS)

Use doctor when you want Merv-Logs without a full custom-report scaffold. These commands only touch logging-related files — not Playwright or Cucumber adapters.

doctor setup-log

Run from your project root (where package.json lives):

npx merv-client doctor setup-log
npm install
npx merv show-logs

Creates or heals:

• merv.properties — merv.report.folder, merv.logger.file, merv.logger.level
• package.json scripts — show-logs, show-report
• merv-client in dependencies when missing

Does not create: jsconfig.json, tsconfig.json, scripts/custom-report.mjs.

doctor set console / unset console

Node can use import { console } from 'merv-client' (or require) so every console.log / info / warn / error / debug / trace also writes to Merv-Logs. Doctor can wire that import across your app automatically.

npx merv-client doctor set console
# run again to toggle off (remove doctor lines)
npx merv-client doctor set console

# remove all doctor-managed imports
npx merv-client doctor unset console

What gets inserted (marked with // merv-doctor-console so unset is safe):

import { console } from 'merv-client'; // merv-doctor-console

import { console } from 'merv-client/browser'; // merv-doctor-console

const { console } = require('merv-client'); // merv-doctor-console

Behavior:

• Scans .js, .jsx, .ts, .tsx, .mjs, .cjs under the project
• Skips node_modules, dist, build, merv-reports, and similar folders
• set console adds the import when a file uses console.* and does not already have a doctor line
• set console removes the doctor import when you run it again on the same file (toggle)
• unset console removes every line tagged // merv-doctor-console (both merv-client and merv-client/browser)
• Vite / React projects: .jsx / .tsx and files with import.meta get merv-client/browser; Node backends get merv-client
• Files with a hand-written merv-client console import (no doctor marker) are skipped

Typical workflow

npx merv-client doctor setup-log
npm install
npx merv-client doctor set console
node src/server.js
npx merv show-logs

MervLogger API

log.info("User {} logged in", username);
log.error("Request failed", exception);

MervLogger.info('After click', { screenshot: await page.screenshot() });

Configuration

Shared keys (project merv.properties and/or classpath mervlogger.properties on Java):

merv.local=true
merv.report.folder=./merv-reports/
merv.logger.level=INFO
merv.logger.file=true

# Optional: send this project's logs to another show-report (combined view)
# merv.log.server=http://127.0.0.1:6174
# merv.log.source=checkout-api

Merv-Logs UI

• Live tail — new lines while your process runs (best with npx merv show-report)
• Load older — scroll up / load previous chunks
• Filter — search text, level, logger name
• Timezone — display timestamps in local or selected zone
• Static fallback — without the Node API, the page can still read log/manifest.json + NDJSON (Java dashboard / Live Server)

On disk: {merv.report.folder}/log/merv-….ndjson, log/manifest.json, merv-logs.html. Java refreshes the HTML page when the local index is rewritten; JS does the same via show-report / report writers.

With frameworks

Java

Use MervLoggerFactory.getLogger(…) from step definitions, listeners, or helpers alongside Cucumber, TestNG, or JUnit 5. No extra dependency beyond merv-client-api.

JavaScript / TypeScript

Install merv-client (plus playwright/cucumber packages as usual). Call MervLogger from hooks, fixtures, or plugin helpers. See Playwright and Cucumber-js.

Suite / testcase labels (Java)

Attach suite and testcase names to NDJSON lines for filtering in Merv-Logs:

import org.teche.merv.client.logging.MervLogContext;

MervLogContext.setSuite("Smoke Suite");
MervLogContext.setTestcase("Login works");
log.info("Navigating to home");
MervLogContext.clear();

On JS, optional { suite, testcase } meta on a log call (or reporter context) fills the same fields. Hand-built MervReport sessions can also attach logger lines to the active testcase — see Custom report.

Troubleshooting

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