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easejs/test/MethodWrappersTest.js

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JavaScript

/**
* Tests method sut
*
* Copyright (C) 2010,2011 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
*/
var common = require( './common' ),
assert = require( 'assert' ),
util = common.require( 'util' ),
sut = common.require( 'MethodWrappers' )
;
/**
* The wrappers accept a function that should return the instance to be bound to
* 'this' when invoking a method. This has some important consequences, such as
* the ability to implement protected/private members.
*/
( function testMethodInvocationBindsThisToPassedInstance()
{
var instance = function() {},
val = 'fooboo',
val2 = 'fooboo2',
iid = 1,
called = false,
getInst = function()
{
called = true;
return instance;
},
method = sut.standard.wrapNew(
function()
{
return this.foo;
},
null, 0, getInst
),
override = sut.standard.wrapOverride(
function()
{
return this.foo2;
},
method, 0, getInst
)
;
// set instance values
instance.foo = val;
instance.foo2 = val2;
assert.equal( method(), val,
"Calling method will bind 'this' to passed instance"
);
assert.equal( override(), val2,
"Calling method override will bind 'this' to passed instance"
);
} )();
/**
* The __super property is defined for method overrides and permits invoking the
* overridden method (method of the supertype).
*
* In this test, we are not looking to assert that __super matches the super
* method. Rather, we want to ensure it /invokes/ it. This is because the super
* method may be wrapped to provide additional functionality. We don't know, we
* don't care. We just want to make sure it's functioning properly.
*/
( function testOverridenMethodShouldContainReferenceToSuperMethod()
{
var orig_called = false,
getInst = function() {},
// "super" method
method = sut.standard.wrapNew(
function()
{
orig_called = true;
},
null, 0, getInst
),
// override method
override = sut.standard.wrapOverride(
function()
{
assert.notEqual(
this.__super,
undefined,
"__super is defined for overridden method"
);
this.__super();
assert.equal(
orig_called,
true,
"Invoking __super calls super method"
);
},
method, 0, getInst
)
;
// invoke the method to run the above assertions
override();
} )();
/**
* If the method is called when bound to a different context (e.g. for
* protected/private members), __super may not be properly bound.
*
* This test is in response to a bug found after implementing visibility
* support. The __super() method was previously defined on 'this', which may or
* may not be the context that is actually used. Likely, it's not.
*/
( function testSuperMethodWorksProperlyWhenContextDiffers()
{
var super_called = false,
retobj = {},
getInst = function()
{
return retobj;
},
// super method to be overridden
method = sut.standard.wrapNew(
function()
{
super_called = true;
},
null, 0, getInst
),
// the overriding method
override = sut.standard.wrapOverride(
function()
{
this.__super();
},
method, 0, getInst
)
;
// call the overriding method
override();
// ensure that the super method was called
assert.equal( super_called, true,
"__super() method is called even when context differs"
);
// finally, ensure that __super is no longer set on the returned object
// after the call to ensure that the caller cannot break encapsulation by
// stealing a method reference (sneaky, sneaky)
assert.equal( retobj.__super, undefined,
"__super() method is unset after being called"
);
} )();
/**
* The proxy wrapper should forward all arguments to the provided object's
* appropriate method. The return value should also be proxied back to the
* caller.
*/
( function testProxyWillProperlyForwardCallToDestinationObject()
{
var name = 'someMethod',
propname = 'dest',
args = [ 1, {}, 'three' ],
args_given = [],
getInst = function()
{
return inst;
},
method_retval = {},
dest = {
someMethod: function()
{
args_given = Array.prototype.slice.call( arguments );
return method_retval;
},
},
// acts like a class instance
inst = { dest: dest },
proxy = sut.standard.wrapProxy( propname, null, 0, getInst, name )
;
assert.strictEqual( method_retval, proxy.apply( inst, args ),
"Proxy call should return the value from the destination"
);
assert.deepEqual( args, args_given,
"All arguments should be properly forwarded to the destination"
);
} )();
/**
* If the destination object returns itself, then we should return the context
* in which the proxy was called; this ensures that we do not break
* encapsulation. Consequently, it also provides a more consistent and sensical
* API and permits method chaining.
*
* If this is not the desired result, then the user is free to forefit the proxy
* wrapper and instead use a normal method, manually proxying the call.
*/
( function testProxyReturnValueIsReplacedWithContextIfDestinationReturnsSelf()
{
var propname = 'foo',
method = 'bar',
foo = {
bar: function()
{
// return "self"
return foo;
}
},
inst = { foo: foo },
ret = sut.standard.wrapProxy(
propname, null, 0,
function()
{
return inst;
},
method
).call( inst )
;
assert.strictEqual( inst, ret,
"Proxy should return instance in place of destination, if returned"
);
} )();
// common assertions between a couple of proxy tests
function proxyErrorAssertCommon( e, prop, method )
{
assert.ok(
e.message.search( 'Unable to proxy' ) > -1,
"Unexpected error received: " + e.message
);
assert.ok(
( ( e.message.search( prop ) > -1 )
&& ( e.message.search( method ) > -1 )
),
"Error should contain property and method names"
);
}
/**
* Rather than allowing a cryptic error to be thrown by the engine, take some
* initiative and attempt to detect when a call will fail due to the destination
* not being an object.
*/
( function testProxyThrowsErrorIfCallWillFailDueToNonObject()
{
var prop = 'noexist',
method = 'foo';
try
{
// should fail because 'noexist' does not exist on the object
sut.standard.wrapProxy(
prop, null, 0,
function() { return {}; },
method
)();
}
catch ( e )
{
proxyErrorAssertCommon( e, prop, method );
return;
}
assert.fail(
"Error should be thrown if proxy would fail due to a non-object"
);
} )();
/**
* Rather than allowing a cryptic error to be thrown by the engine, take some
* initiative and attempt to detect when a call will fail due to the destination
* method not being a function.
*/
( function testProxyThrowsErrorIfCallWillFailDueToNonObject()
{
var prop = 'dest',
method = 'foo';
try
{
// should fail because 'noexist' does not exist on the object
sut.standard.wrapProxy(
prop, null, 0,
function() { return { dest: { foo: 'notafunc' } }; },
method
)();
}
catch ( e )
{
proxyErrorAssertCommon( e, prop, method );
return;
}
assert.fail(
"Error should be thrown if proxy would fail due to a non-function"
);
} )();
/**
* If the `static' keyword is provided, then the proxy mustn't operate on
* instance properties. Instead, the static accessor method $() must be used.
*/
( function testCanProxyToStaticMembers()
{
var getInst = function()
{
// pretend that we're a static class with a static accessor method
return {
$: function( name )
{
// implicitly tests that the argument is properly passed
// (would otherwise return `undefined`)
return s[ name ];
},
};
},
keywords = { 'static': true };
val = [ 'value' ],
s = {
// destination object
foo: {
method: function()
{
return val;
},
}
};
assert.strictEqual( val,
sut.standard.wrapProxy( 'foo', null, 0, getInst, 'method', keywords )(),
"Should properly proxy to static membesr via static accessor method"
);
} )();