You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: pem_test.go
    path of file: ./repos/juju/pki
    
    the code of the file until where you have to start completion: // Copyright 2020 Canonical Ltd.
// Licensed under the AG
    
func (p *PEMSuite) TestCertificateToPemString(c *gc.C) {
	ca, err := pki.NewCA("juju-test-ca", p.signer)
	c.Assert(err, jc.ErrorIsNil)

	certString, err := pki.CertificateToPemString(map[string]string{
		"test": "test-header",
	}, ca)
	c.Assert(err, jc.ErrorIsNil)
	c.Assert(len(certString), jc.GreaterThan, 0)
	//TODO re-enable headers on certificate to pem when Juju upgrade
	//CAAS mongo to something compiled with latest openssl. Currently
	//not all our Openssl versions support pem headers.
	//c.Assert(strings.Contains(certString, "test: test-header"), jc.IsTrue)
	c.Assert(strings.Contains(certString, "BEGIN CERTIFICATE"), jc.IsTrue)
	c.Assert(strings.Contains(certString, "END CERTIFICATE"), jc.IsTrue)
}