Not possible to create custom assertion with no arguments

[doublemarked]

Hello,

A bit new to Nightwatch - but we're trying to make a custom assertion which takes no arguments, and the Page Object command wrapper is naively trying to tweak the first parameter. The assertion we're building, noConsoleErrors, is not element scoped so rightly needs to parameters. It looks something like this:

exports.assertion = function(msg) {
  this.message = msg || `Testing if there are browser console errors`

  // Rest of implementation
};

Usage is like this:

page.assert.noConsoleErrors()

When called in that way (without a message), the command wrapper fails:

✖ TypeError: Cannot read property 'toString' of undefined
    at Object.noConsoleErrors (/project/path/node_modules/nightwatch/lib/page-object/command-wrapper.js:71:37)
    at Object.assertNoErrors (base.js:15:28)

Problem appears to be caused by naive assumptions about available parameters in the command wrapper: https://github.com/nightwatchjs/nightwatch/blob/master/lib/page-object/command-wrapper.js#L71

Are we doing something wrong, or is this a legitimate bug? Is there an obvious work around?

Nightwatch 0.8.18

[beatfactor]

You can just use it on the main nightwatch object, instead of the page.

On Sat, Apr 2, 2016 at 11:19 AM, Heath Morrison [email protected]
wrote:

Hello,

A bit new to Nightwatch - but we're trying to make a custom assertion
which takes no arguments, and the Page Object command wrapper is naively
trying to tweak the first parameter. The assertion we're building,
noConsoleErrors, is not element scoped so rightly needs to parameters. It
looks something like this:

exports.assertion = function(msg) {
this.message = msg || Testing if there are browser console errors

// Rest of implementation
};

Usage is like this:

page.assert.noConsoleErrors()

When called in that way (without a message), the command wrapper fails:

✖ TypeError: Cannot read property 'toString' of undefined
at Object.noConsoleErrors (/project/path/node_modules/nightwatch/lib/page-object/command-wrapper.js:71:37)
at Object.assertNoErrors (base.js:15:28)

Problem appears to be caused by naive assumptions about available
parameters in the command wrapper:
https://github.com/nightwatchjs/nightwatch/blob/master/lib/page-object/command-wrapper.js#L71

Are we doing something wrong, or is this a legitimate bug? Is there an
obvious work around?

Nightwatch 0.8.18

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#924

[doublemarked]

This is what we ended up doing, though it has the minor annoyance of breaking chaining.

[doublemarked]

Wait, so is it not a bug though that the command wrapper doesn't check it's arguments?

[beatfactor]

Oh yes, you're right. I misunderstood the issue.