code: func AssertCertificateIsSignedByCa(t *testing.T, cert *x509.Certificate, signingCa *x509.Certificate) {
  	if err := cert.CheckSignatureFrom(signingCa); err != nil {
  		t.Error("cert is not signed by signing CA as expected")
  	}
  }
docs: // AssertCertificateIsSignedByCa is a utility function for kubeadm testing that asserts if a given certificate is signed
  // by the expected CA