public function testIsMutable()
{
$value = new \stdClass();
$definition = new Property('username', $value);
// Mutate injected value
$value->foo = 'bar';
// Mutate returned value
$definition->getValue()->ping = 'pong';
$expected = StdClassFactory::create(['foo' => 'bar', 'ping' => 'pong']);
$actual = $definition->getValue();
$this->assertEquals($expected, $actual);
}