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: config_test.go
    path of file: ./repos/certmagic
    
    the code of the file until where you have to start completion: // Copyright 2015 Matthew Holt
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//

    
func TestSaveCertResource(t *testing.T) {
	ctx := context.Background()

	am := &ACMEIssuer{CA: "https://example.com/acme/directory"}
	testConfig := &Config{
		Issuers:   []Issuer{am},
		Storage:   &FileStorage{Path: "./_testdata_tmp"},
		Logger:    defaultTestLogger,
		certCache: new(Cache),
	}
	am.config = testConfig

	testStorageDir := testConfig.Storage.(*FileStorage).Path
	defer func() {
		err := os.RemoveAll(testStorageDir)
		if err != nil {
			t.Fatalf("Could not remove temporary storage directory (%s): %v", testStorageDir, err)
		}
	}()

	domain := "example.com"
	certContents := "certificate"
	keyContents := "private key"

	cert := CertificateResource{
		SANs:           []string{domain},
		PrivateKeyPEM:  []byte(keyContents),
		CertificatePEM: []byte(certContents),
		IssuerData: &acme.Certificate{
			URL: "https://example.com/cert",
		},
		issuerKey: am.IssuerKey(),
	}

	err := testConfig.saveCertResource(ctx, am, cert)
	if err != nil {
		t.Fatalf("Expected no error, got: %v", err)
	}

	// the result of our test will be a map, since we have
	// no choice but to decode it into an 'any' interface
	cert.IssuerData = map[string]any{
		"url": "https://example.com/cert",
	}

	siteData, err := testConfig.loadCertResource(ctx, am, domain)
	if err != nil {
		t.Fatalf("Expected no error reading site, got: %v", err)
	}
	if !reflect.DeepEqual(cert, siteData) {
		t.Errorf("Expected '%+v' to match '%+v'", cert, siteData)
	}
}