public function testHasValue()
 {
     $this->assertTrue($this->ds->hasValue('foo'));
     $this->assertTrue($this->ds->hasValue('quux'));
     $this->assertFalse($this->ds->hasValue('something'));
     $this->assertFalse($this->ds->hasValue('foo[key]'));
     $this->assertTrue($this->ds->hasValue('bar'));
     $this->assertTrue($this->ds->hasValue('bar[key]'));
     $this->assertTrue($this->ds->hasValue('bar[nullkey]'));
     $this->assertFalse($this->ds->hasValue('bar[missing]'));
 }