Green tests while non-empty diff

[grebenyuksv-preply]

Dear developers, thanks for the great service you're making. Need you advice, what am I doing wrong?

Problem:
My tests are green where's there IS a visual diff. misMatchTolerance: 0

Expected: test run should be red.

My config:

const path = require('path');
const VisualRegressionCompare = require('wdio-visual-regression-service/compare');

function getScreenshotName(basePath) {
    return function (context) {
        const type = context.type;
        const testName = context.test.title;
        const browserVersion = parseInt(context.browser.version, 10);
        const browserName = context.browser.name;
        const browserViewport = context.meta.viewport;
        const browserWidth = browserViewport.width;
        const browserHeight = browserViewport.height;
        const key = context.options.key || '';

        return path.join(
            basePath,
            `${testName}_${type}_${key}_${browserName}_v${browserVersion}_${browserWidth}x${browserHeight}.png`,
        );
    };
}

exports.config = {
    //
    // ==================
    // Specify Test Files
    // ==================
    // Define which test specs should run. The pattern is relative to the directory
    // from which `wdio` was called. Notice that, if you are calling `wdio` from an
    // NPM script (see https://docs.npmjs.com/cli/run-script) then the current working
    // directory is where your package.json resides, so `wdio` will be called from there.
    //
    services: [
        'visual-regression',
        'screenshots-cleanup',
        'selenium-standalone',
    ],
    visualRegression: {
        compare: new VisualRegressionCompare.LocalCompare({
            referenceName: getScreenshotName(
                path.join(process.cwd(), 'screenshots/reference'),
            ),
            screenshotName: getScreenshotName(
                path.join(process.cwd(), 'screenshots/local/screen'),
            ),
            diffName: getScreenshotName(
                path.join(process.cwd(), 'screenshots/local/diff'),
            ),
            misMatchTolerance: 0,
        }),
        viewportChangePause: 300,
        viewports: [
            // { width: 320, height: 480 },
            // { width: 480, height: 320 },
            { width: 1024, height: 768 },
        ],
        orientations: ['landscape', 'portrait'],
    },
    cleanScreenshotsFolder: {
        folder: 'screenshots/local',
        pattern: '/**/*',
    },
    specs: ['./test/**/*.js'],
    // Patterns to exclude.
    exclude: [
        // 'path/to/excluded/files'
    ],
    //
    // ============
    // Capabilities
    // ============
    // Define your capabilities here. WebdriverIO can run multiple capabilities at the same
    // time. Depending on the number of capabilities, WebdriverIO launches several test
    // sessions. Within your capabilities you can overwrite the spec and exclude options in
    // order to group specific specs to a specific capability.
    //
    // First, you can define how many instances should be started at the same time. Let's
    // say you have 3 different capabilities (Chrome, Firefox, and Safari) and you have
    // set maxInstances to 1; wdio will spawn 3 processes. Therefore, if you have 10 spec
    // files and you set maxInstances to 10, all spec files will get tested at the same time
    // and 30 processes will get spawned. The property handles how many capabilities
    // from the same test should run tests.
    //
    maxInstances: 10,
    //
    // If you have trouble getting all important capabilities together, check out the
    // Sauce Labs platform configurator - a great tool to configure your capabilities:
    // https://docs.saucelabs.com/reference/platforms-configurator
    //
    capabilities: [
        {
            // maxInstances can get overwritten per capability. So if you have an in-house Selenium
            // grid with only 5 firefox instances available you can make sure that not more than
            // 5 instances get started at a time.
            maxInstances: 5,
            //
            browserName: 'chrome',
        },
        {
            // maxInstances can get overwritten per capability. So if you have an in-house Selenium
            // grid with only 5 firefox instances available you can make sure that not more than
            // 5 instances get started at a time.
            maxInstances: 5,
            //
            browserName: 'firefox',
        },
    ],
    //
    // ===================
    // Test Configurations
    // ===================
    // Define all options that are relevant for the WebdriverIO instance here
    //
    // By default WebdriverIO commands are executed in a synchronous way using
    // the wdio-sync package. If you still want to run your tests in an async way
    // e.g. using promises you can set the sync option to false.
    sync: true,
    //
    // Level of logging verbosity: silent | verbose | command | data | result | error
    logLevel: 'verbose',
    //
    // Enables colors for log output.
    coloredLogs: true,
    //
    // Warns when a deprecated command is used
    deprecationWarnings: true,
    //
    // If you only want to run your tests until a specific amount of tests have failed use
    // bail (default is 0 - don't bail, run all tests).
    bail: 0,
    //
    // Saves a screenshot to a given path if a command fails.
    screenshotPath: './errorShots/',
    //
    // Set a base URL in order to shorten url command calls. If your `url` parameter starts
    // with `/`, the base url gets prepended, not including the path portion of your baseUrl.
    // If your `url` parameter starts without a scheme or `/` (like `some/path`), the base url
    // gets prepended directly.
    baseUrl: 'https://stage.preply.com',
    //
    // Default timeout for all waitFor* commands.
    waitforTimeout: 10000,
    //
    // Default timeout in milliseconds for request
    // if Selenium Grid doesn't send response
    connectionRetryTimeout: 90000,
    //
    // Default request retries count
    connectionRetryCount: 3,
    //
    // Initialize the browser instance with a WebdriverIO plugin. The object should have the
    // plugin name as key and the desired plugin options as properties. Make sure you have
    // the plugin installed before running any tests. The following plugins are currently
    // available:
    // WebdriverCSS: https://github.com/webdriverio/webdrivercss
    // WebdriverRTC: https://github.com/webdriverio/webdriverrtc
    // Browserevent: https://github.com/webdriverio/browserevent
    // plugins: {
    //     webdrivercss: {
    //         screenshotRoot: 'my-shots',
    //         failedComparisonsRoot: 'diffs',
    //         misMatchTolerance: 0.05,
    //         screenWidth: [320,480,640,1024]
    //     },
    //     webdriverrtc: {},
    //     browserevent: {}
    // },
    //
    // Test runner services
    // Services take over a specific job you don't want to take care of. They enhance
    // your test setup with almost no effort. Unlike plugins, they don't add new
    // commands. Instead, they hook themselves up into the test process.
    // services: [],//
    // Framework you want to run your specs with.
    // The following are supported: Mocha;, Jasmine, and Cucumber
    // see also: http://webdriver.io/guide/testrunner/frameworks.html
    //
    // Make sure you have the wdio adapter package for the specific framework installed
    // before running any tests.
    framework: 'mocha',
    //
    // Test reporter for stdout.
    // The only one supported by default is 'dot'
    // see also: http://webdriver.io/guide/reporters/dot.html
    reporters: ['dot', 'allure'],
    reporterOptions: {
        allure: {
            outputDir: 'allure-results',
        },
    },
    //
    // Options to be passed to Mocha.
    // See the full list at http://mochajs.org/
    mochaOpts: {
        ui: 'bdd',
        timeout: 99999999,
    },
    //
    // =====
    // Hooks
    // =====
    // WebdriverIO provides several hooks you can use to interfere with the test process in order to enhance
    // it and to build services around it. You can either apply a single function or an array of
    // methods to it. If one of them returns with a promise, WebdriverIO will wait until that promise got
    // resolved to continue.
    /**
     * Gets executed once before all workers get launched.
     * @param {Object} config wdio configuration object
     * @param {Array.<Object>} capabilities list of capabilities details
     */
    // onPrepare: function (config, capabilities) {
    // },
    /**
     * Gets executed just before initialising the webdriver session and test framework. It allows you
     * to manipulate configurations depending on the capability or spec.
     * @param {Object} config wdio configuration object
     * @param {Array.<Object>} capabilities list of capabilities details
     * @param {Array.<String>} specs List of spec file paths that are to be run
     */
    // beforeSession: function (config, capabilities, specs) {
    // },
    /**
     * Gets executed before test execution begins. At this point you can access to all global
     * variables like `browser`. It is the perfect place to define custom commands.
     * @param {Array.<Object>} capabilities list of capabilities details
     * @param {Array.<String>} specs List of spec file paths that are to be run
     */
    // before: function (capabilities, specs) {
    // },
    /**
     * Runs before a WebdriverIO command gets executed.
     * @param {String} commandName hook command name
     * @param {Array} args arguments that command would receive
     */
    // beforeCommand: function (commandName, args) {
    // },

    /**
     * Hook that gets executed before the suite starts
     * @param {Object} suite suite details
     */
    // beforeSuite: function (suite) {
    // },
    /**
     * Function to be executed before a test (in Mocha/Jasmine) or a step (in Cucumber) starts.
     * @param {Object} test test details
     */
    // beforeTest: function (test) {
    // },
    /**
     * Hook that gets executed _before_ a hook within the suite starts (e.g. runs before calling
     * beforeEach in Mocha)
     */
    // beforeHook: function () {
    // },
    /**
     * Hook that gets executed _after_ a hook within the suite ends (e.g. runs after calling
     * afterEach in Mocha)
     */
    // afterHook: function () {
    // },
    /**
     * Function to be executed after a test (in Mocha/Jasmine) or a step (in Cucumber) ends.
     * @param {Object} test test details
     */
    // afterTest: function (test) {
    // },
    /**
     * Hook that gets executed after the suite has ended
     * @param {Object} suite suite details
     */
    // afterSuite: function (suite) {
    // },

    /**
     * Runs after a WebdriverIO command gets executed
     * @param {String} commandName hook command name
     * @param {Array} args arguments that command would receive
     * @param {Number} result 0 - command success, 1 - command error
     * @param {Object} error error object if any
     */
    // afterCommand: function (commandName, args, result, error) {
    // },
    /**
     * Gets executed after all tests are done. You still have access to all global variables from
     * the test.
     * @param {Number} result 0 - test pass, 1 - test fail
     * @param {Array.<Object>} capabilities list of capabilities details
     * @param {Array.<String>} specs List of spec file paths that ran
     */
    // after: function (result, capabilities, specs) {
    // },
    /**
     * Gets executed right after terminating the webdriver session.
     * @param {Object} config wdio configuration object
     * @param {Array.<Object>} capabilities list of capabilities details
     * @param {Array.<String>} specs List of spec file paths that ran
     */
    // afterSession: function (config, capabilities, specs) {
    // },
    /**
     * Gets executed after all workers got shut down and the process is about to exit.
     * @param {Object} exitCode 0 - success, 1 - fail
     * @param {Object} config wdio configuration object
     * @param {Array.<Object>} capabilities list of capabilities details
     */
    // onComplete: function(exitCode, config, capabilities) {
    // }
};

My test:

describe('Google', () => {
    it('Opens up', () => {
        browser.url('https://www.google1.com');
        browser.checkDocument();
    });
});

Repro steps:
Change url to https://www.google.com

Diff produced (correctly):