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From Patrick Mueller <pmue...@gmail.com>
Subject Re: [Node 101] Part 1: Small Modules
Date Sun, 15 Dec 2013 16:46:13 GMT
The big problem with exporting functions - or exporting anything by using
`module.exports =` style of exporting - is recursive require problem.  I
couldn't quickly find any ref to this on the web, so did a little gist:
https://gist.github.com/pmuellr/7975152


On Thu, Dec 12, 2013 at 7:37 PM, Brian LeRoux <b@brian.io> wrote:

> Oh interesting. I can see what you mean though I think the only thing I
> should know about the output is the return value. (In your case, just a
> test for 'done'.) The behavior of the module is super important of course.
> In the small modules philosophy the foo, bar.method, and baz would have
> thier own tests for interface/output to satisfy the case you describe.
>
> Again, IT DEPENDS! The rimraf example is a perfect case for what you
> describe.
>
>
> On Fri, Dec 13, 2013 at 10:59 AM, Gord Tanner <gtanner@gmail.com> wrote:
>
> > It depends what you define as outputs.
> >
> > in a given module:
> >
> > var foo = require('foo'), bar = require('bar'), baz = require('baz');
> >
> > module.exports = function(a, b) {
> >     foo(3);
> >     bar.method(a);
> >     baz(b);
> >
> >    return "done";
> > }
> >
> > I have always counted the calls to foo, bar and baz as output that needs
> to
> > be tested.  This would produce a spec like:
> >
> > "when calling this module":
> >    "it calls foo with 3"
> >    "it calls bar.method with a"
> >    "it calls baz with b"
> >    "it returns done"
> >
> > It is just easier to mock bar.method then foo
> >
> > ie:
> >
> > var rewire = require('rewire');
> > var example = rewire('example');     //NOTE: rewire rather then require
> > example.__set__('foo', jasmine.createSpy());
> >
> > vrs:
> >
> > var example = require('example');
> > var bar = require('bar');
> > spyOn(bar, "method");
> >
> > I came across this problem when using one of Isaac's modules (rimraf [1])
> > where I obviously didn't want to call that in a unit test from my module
> > but I need to mock it out.  Rewire was the only way I could.
> >
> > [1] - https://github.com/isaacs/rimraf
> >
> >
> >
> > On Thu, Dec 12, 2013 at 6:37 PM, Brian LeRoux <b@brian.io> wrote:
> >
> > > ALSO: lets avoid using terms like 'I agree' or 'I disagree'. Its
> > > programming. The answer is ALWAYS 'it depends'. No absolutes in the sea
> > of
> > > change.
> > >
> > >
> > > On Fri, Dec 13, 2013 at 10:34 AM, Brian LeRoux <b@brian.io> wrote:
> > >
> > > > Maybe. Have a look at Substack's code and you'll see he has no
> trouble
> > > > testing. The reason being he tests interfaces and outputs instead of
> > > > implementations. That will be another Node 101!
> > > >
> > > >
> > > > On Fri, Dec 13, 2013 at 10:24 AM, Gord Tanner <gtanner@gmail.com>
> > wrote:
> > > >
> > > >> I also agree with this except for returning a function from
> > > >> module.exports.
> > > >>
> > > >> It is possible but makes mocking much much harder for testing.
> > > >>
> > > >> think of:
> > > >>
> > > >>
> > > >> var foo = require('foo');
> > > >>
> > > >> module.exports = {
> > > >>     awesome: function (a) {
> > > >>         foo(a+1);
> > > >>    }
> > > >> };
> > > >>
> > > >> It is kind of awkward to test this module's use of the foo module.
>  It
> > > can
> > > >> be done with rewire [1] but is a little awkward.
> > > >>
> > > >> If foo was designed where it exported an object literal with
> functions
> > > it
> > > >> would be much easier to mock:
> > > >>
> > > >> var foo = require('foo');
> > > >>
> > > >> module.exports = {
> > > >>     awesome: function (a) {
> > > >>         foo.bar(a+1);
> > > >>    }
> > > >> };
> > > >>
> > > >> it("calls foo.bar", function () {
> > > >>     var foo = require('foo');
> > > >>     spyOn(foo, "bar");
> > > >> });
> > > >>
> > > >> Just my 2 cents from a testing perspective.
> > > >>
> > > >>
> > > >> [1] - https://github.com/jhnns/rewire
> > > >>
> > > >>
> > > >> On Thu, Dec 12, 2013 at 6:06 PM, Brian LeRoux <b@brian.io> wrote:
> > > >>
> > > >> > Create modules that are the smallest possible unit of code. Less
> > code
> > > is
> > > >> > fast code. Faster to write. Faster to maintain. Faster to test.
On
> > the
> > > >> > extreme end characters in the Node community such as Substack
> > > advocate a
> > > >> > single function per module definition.
> > > >> >
> > > >> > module.exports = function() {
> > > >> >   // my logic here
> > > >> > }
> > > >> >
> > > >> > This is kind of extreme and not always possible but a good
> practice
> > > >> > nonetheless. The idea is not new. Its a part of the UNIX
> philosophy:
> > > "do
> > > >> > one thing well" coined by Doug Mcilroy. [1]
> > > >> >
> > > >> > It can help you make code that looks like this [2] into this
[3].
> > > >> >
> > > >> >
> > > >> >
> > > >> > [1]
> > > http://homepage.cs.uri.edu/~thenry/resources/unix_art/ch01s06.html
> > > >> > [2]
> > > >> >
> > > >> >
> > > >>
> > >
> >
> https://github.com/apache/cordova-js/blob/c320378b484a172a02d3ee26634bcc584f43b939/Gruntfile.js
> > > >> > [3] https://github.com/apache/cordova-js/blob/master/Gruntfile.js
> > > >> >
> > > >>
> > > >
> > > >
> > >
> >
>



-- 
Patrick Mueller
http://muellerware.org

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