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easejs/test/test-class-abstract.js

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JavaScript

/**
* Tests abstract classes
*
* Copyright (C) 2010 Mike Gerwitz
*
* This file is part of ease.js.
*
* ease.js is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser 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 Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* @author Mike Gerwitz
* @package test
*/
var common = require( './common' ),
assert = require( 'assert' ),
Class = common.require( 'class' ),
util = common.require( 'util' );
// not abstract
var Foo = Class.extend( {} );
// abstract
var AbstractFoo = Class.extend(
{
ctorCalled: false,
__construct: function()
{
this.ctorCalled = true;
},
'abstract method': [ 'one', 'two', 'three' ],
'abstract second': [],
});
// still abstract (didn't provide a concrete implementation of both abstract
// methods)
var SubAbstractFoo = AbstractFoo.extend(
{
second: function()
{
},
});
// concrete
var ConcreteFoo = AbstractFoo.extend(
{
method: function( one, two, three )
{
},
second: function()
{
},
});
assert.ok(
( Foo.isAbstract instanceof Function ),
"All classes should have an isAbstract() method"
);
assert.equal(
Foo.isAbstract(),
false,
"Classes are not abstract if they contain no abstract methods"
);
assert.equal(
AbstractFoo.isAbstract(),
true,
"Classes should be considered abstract if they contain any abstract methods"
);
assert.equal(
SubAbstractFoo.isAbstract(),
true,
"Subtypes of abstract types are abstract if they don't provide a " +
"concrete implementation for all abstract methods"
);
assert.equal(
ConcreteFoo.isAbstract(),
false,
"Subtypes of abstract types are not abstract if they provide concrete " +
"implementations of all abstract methods"
);
assert.throws( function()
{
new AbstractFoo();
new SubAbstractFoo();
}, Error, "Abstract classes cannot be instantiated" );
assert.ok(
new ConcreteFoo(),
"Concrete subclasses can be instantiated"
);
assert.equal(
( new ConcreteFoo() ).ctorCalled,
true,
"Can call constructors of abstract supertypes"
);
assert.throws( function()
{
AbstractFoo.extend(
{
// incorrect number of arguments
method: function()
{
},
});
}, Error, "Concrete methods must implement the proper number of argments" );
assert.throws(
function()
{
AbstractFoo.extend(
{
// incorrect number of arguments
'abstract method': [],
});
},
TypeError,
"Abstract methods of subtypes must implement the proper number of argments"
);
assert.doesNotThrow(
function()
{
AbstractFoo.extend(
{
// incorrect number of arguments
'abstract method': [ 'one', 'two', 'three', 'four' ],
});
},
Error,
"Abstract methods of subtypes may implement additional arguments, so long" +
"as they implement at least the required number of arguments as defined by " +
"it supertype"
);
assert.doesNotThrow(
function()
{
AbstractFoo.extend(
{
second: function( foo )
{
},
});
},
Error,
"Concrete methods needn't implement the proper number of arguments if " +
"no definition was provided"
);
assert.throws( function()
{
Class.extend(
{
// not an array (invalid)
'abstract foo': 'scalar',
} );
}, TypeError, "Abstract methods must be declared as arrays" );
/**
* There was an issue where the object holding the abstract methods list was not
* checking for methods by using hasOwnProperty(). Therefore, if a method such
* as toString() was defined, it would be matched in the abstract methods list.
* As such, the abstract methods count would be decreased, even though it was
* not an abstract method to begin with (nor was it removed from the list,
* because it was never defined in the first place outside of the prototype).
*
* This negative number !== 0, which causes a problem when checking to ensure
* that there are 0 abstract methods. We check explicitly for 0 for two reasons:
* (a) it's faster than <, and (b - most importantly) if it's non-zero, then
* it's either abstract or something is wrong. Negative is especially wrong. It
* should never be negative!
*/
( function testDoesNotRecognizeObjectPrototypeMembersAsAbstractWhenDefining()
{
assert.doesNotThrow( function()
{
SubAbstractFoo.extend( {
// concrete, so the result would otherwise not be abstract
'method': function( one, two, three ) {},
// the problem
'toString': function() {},
})();
}, Error, "Should not throw error if overriding a prototype method" );
} )();