public function testGetSetCertificateProviderSignatureDate()
 {
     $expectedDate = new \DateTime();
     $expectedDateString = $expectedDate->format(OPGDateFormat::getDateFormat());
     $this->assertTrue($this->poa->setCertificateProviderSignatureDate() instanceof PowerOfAttorney);
     $this->assertEmpty($this->poa->getCertificateProviderSignatureDate());
     $this->assertTrue($this->poa->setCertificateProviderSignatureDateString('') instanceof PowerOfAttorney);
     $this->assertEmpty($this->poa->getCertificateProviderSignatureDateString());
     $this->assertTrue($this->poa->setCertificateProviderSignatureDate($expectedDate) instanceof PowerOfAttorney);
     $this->assertEquals($expectedDate, $this->poa->getCertificateProviderSignatureDate());
     $this->assertEquals($expectedDateString, $this->poa->getCertificateProviderSignatureDateString());
     $this->assertTrue($this->poa->setCertificateProviderSignatureDateString($expectedDateString) instanceof PowerOfAttorney);
     $this->assertEquals($expectedDateString, $this->poa->getCertificateProviderSignatureDateString());
 }