535 lines
16 KiB
JavaScript
535 lines
16 KiB
JavaScript
/**
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* Tests abstract classes
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*
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* Copyright (C) 2014 Mike Gerwitz
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*
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* This file is part of GNU ease.js.
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*
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* ease.js is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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require( 'common' ).testCase(
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{
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caseSetUp: function()
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{
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this.Sut = this.require( 'class_abstract' );
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this.Class = this.require( 'class' );
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},
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/**
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* In order to ensure that the code documents itself, we should require
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* that all classes containing abstract members must themselves be
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* declared as abstract. Otherwise, you are at the mercy of the
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* developer's documentation/comments to know whether or not the class
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* is indeed abstract without looking through its definition.
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*/
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'Must declare classes with abstract members as abstract': function()
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{
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try
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{
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// should fail; class not declared as abstract
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this.Class( 'Foo',
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{
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'abstract foo': [],
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} );
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}
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catch ( e )
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{
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this.assertOk(
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e.message.search( 'Foo' ) !== -1,
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"Abstract class declaration error should contain class name"
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);
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return;
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}
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this.assertFail(
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"Should not be able to declare abstract members unless " +
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"class is also declared as abstract"
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);
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},
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/**
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* Abstract members should be permitted if the class itself is declared
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* as abstract; converse of above test.
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*/
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'Can declare class as abstract': function()
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{
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var Sut = this.Sut;
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this.assertDoesNotThrow( function()
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{
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Sut(
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{
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'abstract foo': [],
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} );
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}, Error );
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},
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/**
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* If a class is declared as abstract, it should contain at least one
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* abstract method. Otherwise, the abstract definition is pointless and
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* unnecessarily confusing---the whole point of the declaration is
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* to produce self-documenting code.
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*/
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'Abstract classes must contain abstract methods': function()
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{
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try
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{
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// should fail; class not declared as abstract
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this.Sut( 'Foo', {} );
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}
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catch ( e )
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{
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this.assertOk(
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e.message.search( 'Foo' ) !== -1,
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"Abstract class declaration error should contain class name"
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);
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return;
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}
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this.assertFail(
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"Abstract classes should contain at least one abstract method"
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);
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},
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/**
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* Abstract methods should remain virtual until they are defined.
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* That is, if a subtype doesn't provide a concrete implementation, it
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* should still be considered virtual.
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*/
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'Abstract methods can be defined concretely by sub-subtypes': function()
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{
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var AbstractFoo = this.Sut( 'Foo',
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{
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'abstract foo': [],
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} ),
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SubAbstractFoo = this.Sut.extend( AbstractFoo, {} );
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var Class = this.Class;
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this.assertDoesNotThrow( function()
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{
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Class.extend( SubAbstractFoo,
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{
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// we should NOT need the override keyword for concrete
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// implementations of abstract super methods
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'foo': function() {},
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} )
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}, Error );
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},
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/**
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* Just as Class contains an extend method, so should AbstractClass.
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*/
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'Abstract class extend method returns new class': function()
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{
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this.assertEqual( typeof this.Sut.extend, 'function',
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"AbstractClass contains extend method"
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);
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this.assertOk(
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this.Class.isClass(
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this.Sut.extend( { 'abstract foo': [] } )
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),
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"Abstract class extend method returns class"
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);
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},
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/**
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* Just as Class contains an implement method, so should AbstractClass.
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* We test implementation further on in this test case.
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*/
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'Abstract class contains implement method': function()
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{
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this.assertEqual( typeof this.Sut.implement, 'function',
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"AbstractClass contains implement method"
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);
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},
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/**
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* All classes should have a method to determine if they are abstract.
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* We test specific cases below.
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*/
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'All classes have an isAbstract() method': function()
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{
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this.assertEqual(
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typeof ( this.Class( {} ).isAbstract ),
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'function'
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);
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},
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/**
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* For this test, note that (as was tested above) a class containing
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* abstract members must be declared as abstract; therefore, this test
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* extends to assert that classes with no abstract methods are not
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* considered to be abstract.
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*/
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'Concrete classes are not considered to be abstract': function()
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{
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this.assertOk( !( this.Class( {} ).isAbstract() ) );
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},
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/**
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* In the same spirit as the preceding test, this extends to asserting
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* that a class containing abstract methods must be considered to be
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* abstract.
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*/
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'Abstract classes are considered to be abstract': function()
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{
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this.assertOk(
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this.Sut( { 'abstract method': [] } ).isAbstract()
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);
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},
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/**
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* In the spirit of the aforementioned, subtypes that do not provide
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* concrete definitions for *all* abstract methods of their supertype
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* must too be considered to be abstract.
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*/
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'Subtypes are abstract if no concrete method is provided': function()
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{
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var Base = this.Sut(
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{
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'abstract foo': [],
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'abstract bar': [],
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} );
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this.assertOk(
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this.Sut.extend( Base,
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{
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// only provide concrete impl. for a single method; `bar' is
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// still abstract
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foo: function() {}
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} ).isAbstract()
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);
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},
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/**
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* Ensure that a subtype is not considered to be abstract if it provides
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* concrete definitions of each of its supertype's abstract methods.
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*/
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'Subtypes are not considered abstract if concrete methods are provided':
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function()
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{
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var Base = this.Sut(
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{
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'abstract foo': [],
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'abstract bar': [],
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} );
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this.assertOk(
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this.Class.extend( Base,
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{
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// provide concrete impls. for both
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foo: function() {},
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bar: function() {},
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} ).isAbstract() === false
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);
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},
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/**
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* Since an abstract class does not provide a complete object
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* description, it cannot be instantiated.
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*/
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'Abstract classes cannot be instantiated': function()
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{
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var Sut = this.Sut;
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this.assertThrows( function()
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{
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Sut( { 'abstract foo': [] } )();
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}, Error );
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},
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/**
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* However, a concrete subtype of an abstract class may be instantiated.
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* Otherwise abstract classes would be pretty useless.
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*/
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'Concrete subtypes of abstract classes can be instantiated': function()
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{
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var Sut = this.Sut;
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this.assertDoesNotThrow( function()
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{
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Sut( { 'abstract foo': [] } )
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.extend( { foo: function() {} } )
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();
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}, Error );
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},
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/**
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* Even though an abstract class itself cannot be instantiated, its
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* constructor may still be inherited (and therefore invoked) through
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* concrete subtypes.
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*/
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'Can call constructors of abstract supertypes': function()
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{
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var ctor_called = false;
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this.Sut(
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{
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__construct: function() { ctor_called = true; },
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'abstract foo': [],
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} ).extend( { foo: function() {} } )();
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this.assertOk( ctor_called );
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},
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/**
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* Abstract methods declare an API strictly for the purpose of ensuring
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* that subtypes are all compatible with respect to that particular
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* field; parameter count, therefore, should be enforced to point out
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* potential bugs to developers. Whether or not the subtype makes use of
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* a particular argument is a separate and unrelated issue.
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*/
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'Concrete methods must implement the proper number of parameters':
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function()
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{
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var Sut = this.Sut;
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this.assertThrows( function()
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{
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// concrete implementation missing parameter `two'
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Sut( { 'abstract foo': [ 'one', 'two' ] } )
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.extend( { foo: function( one ) {} } );
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}, Error );
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},
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/**
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* It may be the case that a subtype wishes to provide a new definition
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* for a particular abstract method---without providing a concrete
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* implementation---to add additional parameters. However, to remain
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* compatible with the supertype, that implementation must provide at
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* least the same number of arguments as the respective method of the
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* supertype.
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*
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* This tests the error condition; see below for the complement.
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*/
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'Abstract methods of subtypes must declare compatible parameter count':
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function()
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{
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var Sut = this.Sut;
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this.assertThrows( function()
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{
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Sut.extend( Sut( { 'abstract foo': [ 'one' ] } ),
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{
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// incorrect number of arguments
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'abstract foo': [],
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} );
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}, TypeError );
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},
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/**
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* Complements the above test to ensure that compatible abstract
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* overrides are permitted.
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*/
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'Abstract members may implement more parameters than supertype':
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function()
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{
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var Sut = this.Sut;
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this.assertDoesNotThrow( function()
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{
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Sut.extend( Sut( { 'abstract foo': [ 'one' ] } ),
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{
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// one greater
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'abstract foo': [ 'one', 'two' ],
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} );
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}, Error );
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},
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/**
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* While this may not necessarily be sensical in all situations, it may
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* be useful for documentation.
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*/
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'Abstract members may implement equal parameters to supertype':
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function()
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{
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var Sut = this.Sut;
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this.assertDoesNotThrow( function()
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{
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Sut.extend( Sut( { 'abstract foo': [ 'one' ] } ),
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{
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// same number
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'abstract foo': [ 'one' ],
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} );
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}, Error );
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},
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/**
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* This test just ensures consistency by ensuring that an empty
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* parameter definition for abstract methods imposes no parameter count
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* requirement on its concrete definition.
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*/
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'Concrete methods have no parameter requirement with empty definition':
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function()
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{
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var Sut = this.Sut;
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this.assertDoesNotThrow( function()
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{
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Sut( { 'abstract foo': [] } ).extend(
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{
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foo: function() {}
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} );
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}, Error );
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},
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/**
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* An abstract method is represented by an array listing its parameters
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* (that must be implemented by concrete definitions).
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*/
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'Abstract methods must be declared as arrays': function()
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{
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var Class = this.Class;
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this.assertThrows( function()
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{
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// likely demonstrates misunderstanding of the syntax
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Class.extend( { 'abstract foo': function() {} } );
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}, TypeError, "Abstract method cannot be declared as a function" );
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this.assertThrows( function()
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{
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// might be common mistake for attempting to denote a single
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// parameter; pure speculation.
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Class.extend( { 'abstract foo': 'scalar' } );
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}, TypeError, "Abstract method cannot be declared as a scalar" );
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},
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/**
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* There was an issue where the object holding the abstract methods list
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* was not checking for methods by using hasOwnProperty(). Therefore, if
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* a method such as toString() was defined, it would be matched in the
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* abstract methods list. As such, the abstract methods count would be
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* decreased, even though it was not an abstract method to begin with
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* (nor was it removed from the list, because it was never defined in
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* the first place outside of the prototype).
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*
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* This negative number !== 0, which causes a problem when checking to
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* ensure that there are 0 abstract methods. We check explicitly for 0
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* because, if it's non-zero, then it's either abstract or something is
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* wrong. Negative is especially wrong. It should never be negative!
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*/
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'Does not recognize object prototype members as abstract': function()
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{
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var Sut = this.Sut;
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this.assertDoesNotThrow( function()
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{
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Sut( { 'abstract method': [] } ).extend(
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{
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// concrete, so the result would otherwise not be abstract
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method: function() {},
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// the problem---this exists in the prototype chain of every
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// object
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'toString': function() {},
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})();
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}, Error );
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},
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/**
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* Ensure we support named abstract class extending
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*/
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'Can create named abstract subtypes': function()
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{
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this.assertOk(
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this.Sut( 'Named' ).extend(
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this.Sut( { 'abstract foo': [] } ),
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{}
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).isAbstract()
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);
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},
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/**
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* Abstract classes, when extended, should yield a concrete class by
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* default. Otherwise, the user should once again use AbstractClass to
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* clearly state that the subtype is abstract. Remember:
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* self-documenting.
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*/
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'Calling extend() on abstract class yields concrete class': function()
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{
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var Foo = this.Sut( { 'abstract foo': [] } ),
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cls_named = this.Sut( 'NamedSubFoo' ).extend( Foo, {} ),
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cls_anon = this.Sut.extend( Foo, {} );
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var Class = this.Class;
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// named
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this.assertThrows(
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function()
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{
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// should throw an error, since we're not declaring it as
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// abstract and we're not providing a concrete impl
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Class.isAbstract( cls_named.extend( {} ) );
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},
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TypeError,
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"Extending named abstract classes should be concrete"
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);
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// anonymous
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this.assertThrows(
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function()
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{
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// should throw an error, since we're not declaring it as abstract
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// and we're not providing a concrete impl
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Class.isAbstract( cls_anon.extend( {} ) );
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},
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TypeError,
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"Extending anonymous abstract classes should be concrete"
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);
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},
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/**
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* Extending an abstract class after an implement() should still result
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* in an abstract class. Essentially, we are testing to ensure that the
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* extend() method is properly wrapped to flag the resulting class as
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* abstract. This was a bug.
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*/
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'Implementing interfaces will preserve abstract class definition':
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function()
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{
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var Sut = this.Sut,
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Interface = this.require( 'interface' );
|
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this.assertOk(
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// if not considered abstract, extend() will fail, as it will
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// contain abstract member foo
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Sut( 'TestImplExtend' )
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.implement( Interface( { foo: [] } ) )
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.extend( {} )
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.isAbstract()
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);
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},
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} );
|