function testIsValidRequiredField()
 {
     $f = new Tracker_FormElement_Field_DateTestVersion();
     $f->setReturnValue('isRequired', true);
     $a = new MockTracker_Artifact();
     $this->assertTrue($f->isValid($a, '2009-08-31'));
     $this->assertFalse($f->isValid($a, '2009-08-45'));
     $this->assertFalse($f->isValid($a, '2009-13-06'));
     $this->assertFalse($f->isValid($a, '20091306'));
     $this->assertFalse($f->isValid($a, '06/12/2009'));
     $this->assertFalse($f->isValid($a, '06-12-2009'));
     $this->assertFalse($f->isValid($a, 'foobar'));
     $this->assertFalse($f->isValid($a, 06 / 12 / 2009));
     $this->assertFalse($f->isValidRegardingRequiredProperty($a, ''));
     $this->assertFalse($f->isValidRegardingRequiredProperty($a, null));
 }