Confusing error message

I have the following scenario (greatly simplify to demonstrate the issue):

shared.js -- can be reused in multiple page objects:
module.exports = function Shared() {
    return {
        selector: 'form',
        sections: {
            field: {
                selector: '.field',
                elements: {
                    label: '.label',
                },
                commands: [{
                    verify: function (input) {
                        this
                            .waitForElementVisible('@value');
                    },
                }],
            },
        },
    };
};

test.js--page object that uses shared.js:
var Shared = require('./shared');

module.exports = {
    sections: {
        form: {
            selector: '.test',
            sections: {
                shared: new Shared(),
            },
        },
    },
};

test1.js -- uses the test.js page object, which included the shared PO code:
module.exports = {
    before: function (browser) {
        browser.test = browser.page.test();
    },
    after: function (browser) {
        browser.end();
    },
    'Do something': function (browser) {
    },
};

test2.js -- uses the test.js page object, which included the shared PO code:
module.exports = {
    before: function (browser) {
        browser.test = browser.page.test();
    },
    after: function (browser) {
        browser.end();
    },
    'Do something': function (browser) {
    },
};

NOTE: Both test1.js and test2.js are under a group directory (e.g. groupTest)

Running the above with our test server…something like this:

node test/e2e/server.js --env default --config ./test/e2e/nightwatch.json --group test/e2e/tests/groupTest

results in the following:

Error: The command "AssertionError" is already defined!
    at addCommand (C:\Users\git\prs\node_modules\nightwatch\lib\page-object\command-wrapper.js:162:19)
    at C:\Users\git\prs\node_modules\nightwatch\lib\page-object\command-wrapper.js:147:48
    at Array.forEach (native)
    at C:\Users\git\prs\node_modules\nightwatch\lib\page-object\command-wrapper.js:146:33
    at Array.forEach (native)
    at applyCommandsToTarget (C:\Users\git\prs\node_modules\nightwatch\lib\page-object\command-wrapper.js:139:27)
    at module.exports.commandName.addWrappedCommands (C:\Users\git\prs\node_modules\nightwatch\lib\page-object\command-wrapper.js:184:5)
    at new Section (C:\Users\git\prs\node_modules\nightwatch\lib\page-object\section.js:31:18)
    at C:\Users\git\prs\node_modules\nightwatch\lib\page-object\page-utils.js:65:34
    at Array.forEach (native)
    at module.exports.createSections (C:\Users\git\prs\node_modules\nightwatch\lib\page-object\page-utils.js:61:27)
    at new Section (C:\Users\git\prs\node_modules\nightwatch\lib\page-object\section.js:28:6)
    at C:\Users\git\prs\node_modules\nightwatch\lib\page-object\page-utils.js:65:34
    at Array.forEach (native)
    at module.exports.createSections (C:\Users\git\prs\node_modules\nightwatch\lib\page-object\page-utils.js:61:27)
    at new Section (C:\Users\git\prs\node_modules\nightwatch\lib\page-object\section.js:28:6)

That’s an extremely confusing error when the simple fix is to replace the following line in shared.js:

verify: function (input) {

to something else…for example:

verifyX: function (input) {

Perhaps verify is a reserved word in nightwatch?

[scottymo]

Like @vietnogi , very glad I found this page… I ran into the same problem, and naming my PO command to something other than “verify” fixed it.

@zelein My guess is that in your case, you may have done an “npm update” or “npm install” that pulled down new versions of your node packages, and somewhere in the new packages it pulled down was code that defined a verify() function (probably in the NightwatchJS code related to initializing page objects… not sure though).

In my case, I would not get the error the first time I created the page object that had a verify() function. But the second time in the code that created that PO–boom! Confusing “Error: The command “AssertionError” is already defined!”.

Anyways, thanks a bunch @webteckie for posting this, you saved me a lot of time digging around the code to try to find the problem!

[stale[bot]]

This issue has been automatically marked as stale because it has not had any recent activity. If possible, please retry using the latest Nightwatch version and update the issue with any relevant details. If no further activity occurs, it will be closed. Thank you for your contribution.