CaspserJS assertEval with variables - casperjs

Question

I'd like to use CasperJS to evaluate a variable equals a certain value.
I simplified my exemple as much as I could that way:
var testDate = "24/03/14";
casper.test.begin('TEST', 1, function suite(test) {
casper.start('http://www.google.com/', function() {
this.test.assertEval(function() {
return testDate == "24/03/14";
}, "testDate is 24/03/14" );
});
casper.run(function() {
this.test.done();
});
});
I don't know why it fails, here is what I get in my console:
Test file: tests.js
#TEST
FAIL testDate is 24/03/14
# type: assertEval
# file: tests.js:7
# code: }, "testDate is 24/03/14" );
# subject: null
# fn: undefined
# params: undefined
FAIL 1 test executed in 2.896s, 0 passed, 1 failed, 0 dubious, 0 skipped.
Details for the 1 failed test:
In tests.js:7
TEST
assertEval: testDate is 24/03/14
Any idea ?
UPDATE
I realised my simplified example was faulty, it didn't represent what I really needed.
Actually, what I want to achieve is to test if a variable from the current page DOM context equals a local variable.

Answer 1

As per manual Asserteval:
Asserts that a code evaluation in remote DOM strictly resolves to a boolean true:
your testdate variable is local to the casperjs script and is not accessible in the remote dom. You would have to inject it to the window like described here.

Answer 2

Ok found the answer myself.
To test if a variable from the current page DOM context equals a local variable, I realised I could use a simple assertEvalEquals():
test.assertEvalEquals(function() {
return variableFromPageDomContext;
}, localVariable);
Likewise, when testing if a variable from the current page DOM context matches a RegExp pattern, we have to use evaluate() to get the variable from the DOM as the first parameter of an assertMatch():
test.assertMatch(this.evaluate(function() {
return variableFromPageDomContext;
}), RegExpPattern);
Hope that can help.

Answer 3

As #Surreal answers its possible to use the assertEvalEquals() passing the function and the expected value.
However the original question wants to pass a variable from casperjs context to assertEval() function, you can simply do it as follows, passing to assertEval() three arguments: the function which receive the value, a message for the assert and the value:
var varPassToEval = 'someValue';
test.assertEval(
function(varFromCasperContext){
return varFromPageDomContext === varFromCasperContext;
},
'Assert Eval to test',
varPassToEval
);
With the above example probably is clear to use assertEvalEquals() however could be useful for more complex cases, for example imagine that you want to check if a text appears in a some <li> inside <ul> in DOM which it's dynamic and can change but you don't know at first where your text is... for this case you can use:
var somePartOfText = 'blue';
test.assertEval(
function(varFromCasperContext){
return document.getElementsByTagName("ul")[0].textContent.indexOf(varFromCasperContext) != -1;
},
'Assert Eval to test',
somePartOfText
);
Hope it helps,