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easejs/test/test-class-implement.js

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/**
* Tests class interface implement method
*
* Copyright (C) 2010, 2011, 2013 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/>.
*
* @author Mike Gerwitz
*/
var common = require( './common' ),
assert = require( 'assert' ),
Class = common.require( 'class' ),
Interface = common.require( 'interface' ),
AbstractClass = common.require( 'class_abstract' )
;
// test with and without abstract keyword
var Type = Interface.extend( {
'abstract foo': [],
}),
Type2 = Interface.extend( {
foo2: [],
}),
Foo = {},
PlainFoo = Class.extend(),
PlainFoo2 = {}
;
require( 'common' ).testCase(
{
'Class exports contain implement method for no base class': function()
{
this.assertOk(
( Class.implement instanceof Function ),
"Class provides method to implement interfaces"
);
},
'Clsss object contains implement method for self as base': function()
{
this.assertOk(
( PlainFoo.implement instanceof Function ),
"Classes contain an implement() method"
);
},
'Can implement interface from an empty base': function()
{
this.assertDoesNotThrow( function()
{
Class.implement( Type, Type2 );
}, Error, "Class can implement interfaces" );
},
/**
* Initially, the implement() method returned an abstract class. However, it
* doesn't make sense to create a class without any actual definition (and
* there's other implementation considerations that caused this route to be
* taken). One wouldn't do "class Foo implements Type", and not provide any
* body.
*
* Therefore, implement() should return nothing useful until extend() is
* called on it.
*/
'Result of implement is not usable as a class': function()
{
var result = Class.implement( Type );
this.assertEqual(
( Class.isClass( result ) ),
false,
"Result of implement operation on class is not usable as a Class"
);
},
/**
* As a consequence of the above, we must extend with an empty definition
* (base) in order to get our abstract class.
*/
'Abstract methods are copied into new class using empty base': function()
{
Foo = AbstractClass.implement( Type, Type2 ).extend( {} );
this.assertOk(
( ( Foo.prototype.foo instanceof Function )
&& ( Foo.prototype.foo2 instanceof Function )
),
"Abstract methods are copied into the new class prototype " +
"(empty base)"
);
},
'Can implement interface atop an exist class': function()
{
this.assertDoesNotThrow( function()
{
PlainFoo.implement( Type, Type2 );
}, Error, "Classes can implement interfaces" );
},
/**
* Ensure the same system mentioned above also applies to the extend()
* method on existing classes
*/
'Implementing interface atop existing class not usable by default':
function()
{
var result = PlainFoo.implement( Type );
this.assertEqual(
( Class.isClass( result ) ),
false,
"Result of implementing interfaces on an existing base is not " +
"usable as a Class"
);
},
'Abstract method copied into new class using existing base': function()
{
PlainFoo2 = AbstractClass.implement( Type, Type2 )
.extend( PlainFoo, {} );
this.assertOk(
( ( PlainFoo2.prototype.foo instanceof Function )
&& ( PlainFoo2.prototype.foo2 instanceof Function )
),
"Abstract methods are copied into the new class prototype " +
"(concrete base)"
);
},
/**
* Since interfaces can contain only abstract methods, it stands to reason
* that any class implementing an interface without providing any concrete
* methods should be abstract by default.
*/
'Classes implementing interfaces are considered abstract by default':
function()
{
this.assertEqual(
( Foo.isAbstract() && PlainFoo2.isAbstract() ),
true,
"Classes that implements interface(s) are considered abstract if " +
"the implemented methods have no concrete implementations"
);
},
'Instances of classes are instances of their implemented interfaces':
function()
{
// concrete implementation so that we can instantiate it
var ConcreteFoo = Foo.extend(
{
'foo': function() {},
'foo2': function() {},
}),
concrete_inst = ConcreteFoo()
;
this.assertOk(
( concrete_inst.isInstanceOf( Type )
&& concrete_inst.isInstanceOf( Type2 )
),
"Instances of classes implementing interfaces are considered to " +
"be instances of the implemented interfaces"
);
this.assertEqual(
ConcreteFoo.isAbstract(),
false,
"Concrete implementations are not considered to be abstract"
);
},
/**
* Consider the following scenario:
*
* MyClass.implement( Type ).extend( MyOtherClass, {} );
*
* What the above is essentially saying is: "I'd like to extend MyClass by
* implementing Type. Oh, no, wait, I'd actually like it to extend
* MyOtherClass." That doesn't make sense! Likely, it's unintended. Prevent
* confusion and bugs. Throw an error.
*/
'Cannot specify parent after implementing atop existing class': function()
{
this.assertThrows( function()
{
// should not be permitted
PlainFoo.implement( Type, Type2 ).extend( PlainFoo2, {} );
},
Error,
"Cannot specify new parent for extend() when implementing from " +
"existing class"
);
},
/**
* Opposite of the above test. If a parent wasn't specified to begin with,
* then we're fine to specify it in extend().
*/
'Can specify parent if implementing atop empty class': function()
{
this.assertDoesNotThrow(
function()
{
// this /should/ work
AbstractClass.implement( Type ).extend( PlainFoo, {} );
},
Error,
"Can specify parent for exetnd() when implementing atop an " +
"empty base"
);
},
/**
* If more than two arguments are given to extend(), then the developer
* likely does not understand the API. Throw an error to prevent some
* bugs/confusion.
*/
'Throws exception if extend contains too many arguments': function()
{
this.assertThrows( function()
{
Class.implement( Type ).extend( PlainFoo, {}, 'extra' );
}, Error, "extend() after implementing accepts no more than two args" );
},
} );