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Add propertyDescriptor assertion #408

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merged 1 commit into from Mar 30, 2015
Merged

Add propertyDescriptor assertion #408

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49 changes: 49 additions & 0 deletions lib/chai/core/assertions.js
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Expand Up @@ -888,6 +888,55 @@ module.exports = function (chai, _) {
Assertion.addMethod('ownProperty', assertOwnProperty);
Assertion.addMethod('haveOwnProperty', assertOwnProperty);

/**
* ### .ownPropertyDescriptor(name[, descriptor[, message]])
*
* Asserts that the target has an own property descriptor `name`, that optionally matches `descriptor`.
*
* expect('test').to.have.ownPropertyDescriptor('length');
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Could you please add a few more examples here? Specifically I'd like to see the following:

expect('test').to.have.ownPropertyDescriptor('length', { enumerable: false, configurable: false, writable: false, value: 4 });
expect('test').ownPropertyDescriptor('length').to.have.property('enumerable', false);
expect('test').ownPropertyDescriptor('length').to.have.keys('value');

Feel free to adjust those as you see fit - but it should show a couple of examples to demonstrate what's possible (especially for any extra arguments).

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Sure, those look great :-)

* expect('test').to.have.ownPropertyDescriptor('length', { enumerable: false, configurable: false, writable: false, value: 4 });
* expect('test').not.to.have.ownPropertyDescriptor('length', { enumerable: false, configurable: false, writable: false, value: 3 });
* expect('test').ownPropertyDescriptor('length').to.have.property('enumerable', false);
* expect('test').ownPropertyDescriptor('length').to.have.keys('value');
*
* @name ownPropertyDescriptor
* @alias haveOwnPropertyDescriptor
* @param {String} name
* @param {Object} descriptor _optional_
* @param {String} message _optional_
* @api public
*/

function assertOwnPropertyDescriptor (name, descriptor, msg) {
if (typeof descriptor === 'string') {
msg = descriptor;
descriptor = null;
}
if (msg) flag(this, 'message', msg);
var obj = flag(this, 'object');
var actualDescriptor = Object.getOwnPropertyDescriptor(Object(obj), name);
if (actualDescriptor && descriptor) {
this.assert(
_.eql(descriptor, actualDescriptor)
, 'expected the own property descriptor for ' + _.inspect(name) + ' on #{this} to match ' + _.inspect(descriptor) + ', got ' + _.inspect(actualDescriptor)
, 'expected the own property descriptor for ' + _.inspect(name) + ' on #{this} to not match ' + _.inspect(descriptor)
, descriptor
, actualDescriptor
, true
);
} else {
this.assert(
actualDescriptor
, 'expected #{this} to have an own property descriptor for ' + _.inspect(name)
, 'expected #{this} to not have an own property descriptor for ' + _.inspect(name)
);
}
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Logic could be cleaned up here to avoid the this.assert(true):

    if (descriptor) {
      this.assert(
          _.eql(descriptor, actualDescriptor)
        , 'expected the own property descriptor for ' + _.inspect(name) + ' on #{this} to match ' + _.inspect(descriptor) + ', got ' + _.inspect(actualDescriptor)
        , 'expected the own property descriptor for ' + _.inspect(name) + ' on #{this} to not match ' + _.inspect(descriptor)
        , descriptor
        , actualDescriptor
        , true
      );
    } else {
      this.assert(
          actualDescriptor
        , 'expected #{this} to have an own property descriptor for ' + _.inspect(name)
        , 'expected #{this} to not have an own property descriptor for ' + _.inspect(name)
      );
    }

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Hmm - the way you've changed it, if descriptor is passed but actualDescriptor is not present, then the wording won't be as clear imo that the property descriptor wasn't there at all. In other words, if the actualDescriptor is not present, it doesn't really matter what you passed as descriptor the actionable test failure is "the property didn't exist", not "it didn't match".

However, I think I can tweak it to avoid the assert(true) which I think is the purpose of your comment :-)

Fix incoming.

flag(this, 'object', actualDescriptor);
}

Assertion.addMethod('ownPropertyDescriptor', assertOwnPropertyDescriptor);
Assertion.addMethod('haveOwnPropertyDescriptor', assertOwnPropertyDescriptor);

/**
* ### .length(value)
*
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36 changes: 35 additions & 1 deletion test/expect.js
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Expand Up @@ -467,7 +467,7 @@ describe('expect', function () {
err(function(){
expect(deepObj).to.have.deep.property('teas[3].tea', 'bar');
}, "expected { Object (green, teas) } to have a deep property 'teas[3].tea'");

var arr = [
[ 'chai', 'matcha', 'konacha' ]
, [ { tea: 'chai' }
Expand Down Expand Up @@ -531,6 +531,40 @@ describe('expect', function () {
}, "blah: expected { length: 12 } to not have own property 'length'");
});

it('ownPropertyDescriptor(name)', function(){
expect('test').to.have.ownPropertyDescriptor('length');
expect('test').to.haveOwnPropertyDescriptor('length');
expect('test').not.to.have.ownPropertyDescriptor('foo');

var obj = {};
var descriptor = {
configurable: false,
enumerable: true,
writable: true,
value: NaN
};
Object.defineProperty(obj, 'test', descriptor);
expect(obj).to.have.ownPropertyDescriptor('test', descriptor);
err(function(){
expect(obj).not.to.have.ownPropertyDescriptor('test', descriptor, 'blah');
}, "blah: expected the own property descriptor for 'test' on { test: NaN } to not match { configurable: false,\n enumerable: true,\n writable: true,\n value: NaN }");
err(function(){
var wrongDescriptor = {
configurable: false,
enumerable: true,
writable: false,
value: NaN
};
expect(obj).to.have.ownPropertyDescriptor('test', wrongDescriptor, 'blah');
}, "blah: expected the own property descriptor for 'test' on { test: NaN } to match { configurable: false,\n enumerable: true,\n writable: false,\n value: NaN }, got { value: NaN,\n writable: true,\n enumerable: true,\n configurable: false }");

err(function(){
expect(obj).to.have.ownPropertyDescriptor('test2', 'blah');
}, "blah: expected { test: NaN } to have an own property descriptor for 'test2'");

expect(obj).to.have.ownPropertyDescriptor('test').and.have.property('enumerable', true);
});

it('string()', function(){
expect('foobar').to.have.string('bar');
expect('foobar').to.have.string('foo');
Expand Down
34 changes: 34 additions & 0 deletions test/should.js
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Expand Up @@ -396,6 +396,40 @@ describe('should', function() {
}, "blah: expected { length: 12 } to not have own property 'length'");
});

it('ownPropertyDescriptor(name)', function(){
'test'.should.haveOwnPropertyDescriptor('length');
'test'.should.have.ownPropertyDescriptor('length');
'test'.should.not.have.ownPropertyDescriptor('foo');

var obj = { };
var descriptor = {
configurable: false,
enumerable: true,
writable: true,
value: NaN
};
Object.defineProperty(obj, 'test', descriptor);
obj.should.haveOwnPropertyDescriptor('test', descriptor);
err(function(){
obj.should.not.haveOwnPropertyDescriptor('test', descriptor, 'blah');
}, "blah: expected the own property descriptor for 'test' on { test: NaN } to not match { configurable: false,\n enumerable: true,\n writable: true,\n value: NaN }");
err(function(){
var wrongDescriptor = {
configurable: false,
enumerable: true,
writable: false,
value: NaN
};
obj.should.haveOwnPropertyDescriptor('test', wrongDescriptor, 'blah');
}, "blah: expected the own property descriptor for 'test' on { test: NaN } to match { configurable: false,\n enumerable: true,\n writable: false,\n value: NaN }, got { value: NaN,\n writable: true,\n enumerable: true,\n configurable: false }");

err(function(){
obj.should.haveOwnPropertyDescriptor('test2', 'blah');
}, "blah: expected { test: NaN } to have an own property descriptor for 'test2'");

obj.should.have.ownPropertyDescriptor('test').and.have.property('enumerable', true);
});

it('string()', function(){
'foobar'.should.contain.string('bar');
'foobar'.should.contain.string('foo');
Expand Down