if der == nil {
		t.Fatal("Failed to find PEM block")
	}

	cert, err := ParseCertificate(der.Bytes)
	if err != nil {
		t.Fatal(err)
	}

	if err = cert.CheckSignature(ECDSAWithSHA256, nil, nil); err == nil {
		t.Fatal("CheckSignature unexpectedly return no error")
	}

	const expectedSubstring = " but have public key of type "
	if !strings.Contains(err.Error(), expectedSubstring) {