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easejs/test/Trait/AbstractTest.js

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/**
* Tests abstract trait definition and use
*
* Copyright (C) 2014 Mike Gerwitz
*
* This file is part of GNU ease.js.
*
* ease.js is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
require( 'common' ).testCase(
{
caseSetUp: function()
{
this.Sut = this.require( 'Trait' );
this.Class = this.require( 'class' );
this.AbstractClass = this.require( 'class_abstract' );
},
/**
* If a trait contains an abstract member, then any class that uses it
* should too be considered abstract if no concrete implementation is
* provided.
*/
'Abstract traits create abstract classes when used': function()
{
var T = this.Sut( { 'abstract foo': [] } );
var _self = this;
this.assertDoesNotThrow( function()
{
// no concrete `foo; should be abstract (this test is sufficient
// because AbstractClass will throw an error if there are no
// abstract members)
_self.AbstractClass.use( T ).extend( {} );
}, Error );
},
/**
* A class may still be concrete even if it uses abstract traits so long
* as it provides concrete implementations for each of the trait's
* abstract members.
*/
'Concrete classes may use abstract traits by definining members':
function()
{
var T = this.Sut( { 'abstract traitfoo': [ 'foo' ] } ),
C = null,
called = false;
var _self = this;
this.assertDoesNotThrow( function()
{
C = _self.Class.use( T ).extend(
{
traitfoo: function( foo ) { called = true; },
} );
} );
// sanity check
C().traitfoo();
this.assertOk( called );
},
/**
* The concrete methods provided by a class must be compatible with the
* abstract definitions of any used traits. This test ensures not only
* that the check is being performed, but that the abstract declaration
* is properly inherited from the trait.
*
* TODO: The error mentions "supertype" compatibility, which (although
* true) may be confusing; perhaps reference the trait that declared the
* method as abstract.
*/
'Concrete classes must be compatible with abstract traits': function()
{
var T = this.Sut( { 'abstract traitfoo': [ 'foo' ] } );
var _self = this;
this.assertThrows( function()
{
C = _self.Class.use( T ).extend(
{
// missing param in definition
traitfoo: function() {},
} );
} );
},
/**
* If a trait defines an abstract method, then it should be able to
* invoke a concrete method of the same name defined by a class.
*/
'Traits can invoke concrete class implementation of abstract method':
function()
{
var expected = 'foobar';
var T = this.Sut(
{
'public getFoo': function()
{
return this.echo( expected );
},
'abstract protected echo': [ 'value' ],
} );
var result = this.Class.use( T ).extend(
{
// concrete implementation of abstract trait method
'protected echo': function( value )
{
return value;
},
} )().getFoo();
this.assertEqual( result, expected );
},
/**
* Even more kinky is when a trait provides a concrete implementation
* for an abstract method that is defined in another trait that is mixed
* into the same class. This makes sense, because that class acts as
* though the trait's abstract method is its own. This allows for
* message passing between two traits with the class as the mediator.
*
* This is otherwise pretty much the same as the above test. Note that
* we use a public `echo' method; this is to ensure that we do not break
* in the event that protected trait members break (that is: are not
* exposed to the class).
*/
'Traits can invoke concrete trait implementation of abstract method':
function()
{
var expected = 'traitbar';
// same as the previous test
var Ta = this.Sut(
{
'public getFoo': function()
{
return this.echo( expected );
},
'abstract public echo': [ 'value' ],
} );
// but this is new
var Tc = this.Sut(
{
// concrete implementation of abstract trait method
'public echo': function( value )
{
return value;
},
} );
this.assertEqual(
this.Class.use( Ta, Tc ).extend( {} )().getFoo(),
expected
);
// order shouldn't matter (because that'd be confusing and
// frustrating to users, depending on how the traits are named), so
// let's do this again in reverse order
this.assertEqual(
this.Class.use( Tc, Ta ).extend( {} )().getFoo(),
expected,
"Crap; order matters?!"
);
},
} );