Negative value SPTween bug

MyTest.h

#import <SenTestingKit/SenTestingKit.h>

@interface MyTest : SenTestCase

@end

MyTest.m

#import "MyTest.h"
#import "Sparrow.h"

@interface MyTest()

@property (nonatomic) int testProp;

@end


@implementation JTFinalScorePaneTest

@synthesize testProp;

- (void)testSpTween
{
    self.testProp = 100;
    
    SPStage *fakeStage = [[[SPStage alloc] initWithWidth:0 height:0] autorelease];
    
    SPTween *testedTween = [SPTween tweenWithTarget:self time:1];
    [testedTween animateProperty:@"testProp" targetValue:-100];
    [fakeStage.juggler addObject:testedTween];
    
    [fakeStage.juggler advanceTime:1];
    
    STAssertEquals(self.testProp, -100, @"tween didn't finish although time has passed"); // fails - actual value is '-99'
}