public void Validators_Issuer()
        {
            List <string> issuers = new List <string> {
                "", IdentityUtilities.DefaultIssuer
            };
            List <string> invalidIssuers = new List <string> {
                "", IdentityUtilities.NotDefaultIssuer
            };

            RunIssuerTest(issuer: null, securityToken: null, validationParameters: null, ee: ExpectedException.ArgumentNullException());
            RunIssuerTest(issuer: null, securityToken: null, validationParameters: new TokenValidationParameters {
                ValidateIssuer = false
            }, ee: ExpectedException.NoExceptionExpected);
            RunIssuerTest(issuer: null, securityToken: null, validationParameters: new TokenValidationParameters(), ee: ExpectedException.SecurityTokenInvalidIssuerException(substringExpected: "IDX10211:"));
            RunIssuerTest(issuer: IdentityUtilities.DefaultIssuer, securityToken: null, validationParameters: new TokenValidationParameters(), ee: ExpectedException.SecurityTokenInvalidIssuerException(substringExpected: "IDX10204:"));
            RunIssuerTest(issuer: IdentityUtilities.DefaultIssuer, securityToken: null, validationParameters: new TokenValidationParameters {
                ValidIssuer = IdentityUtilities.NotDefaultIssuer
            }, ee: ExpectedException.SecurityTokenInvalidIssuerException(substringExpected: "IDX10205:"));
            RunIssuerTest(issuer: IdentityUtilities.DefaultIssuer, securityToken: null, validationParameters: new TokenValidationParameters {
                ValidIssuers = invalidIssuers
            }, ee: ExpectedException.SecurityTokenInvalidIssuerException(substringExpected: "IDX10205:"));
            RunIssuerTest(issuer: IdentityUtilities.DefaultIssuer, securityToken: null, validationParameters: new TokenValidationParameters {
                ValidIssuer = IdentityUtilities.DefaultIssuer
            }, ee: ExpectedException.NoExceptionExpected);
            RunIssuerTest(issuer: IdentityUtilities.DefaultIssuer, securityToken: null, validationParameters: new TokenValidationParameters {
                ValidIssuers = issuers
            }, ee: ExpectedException.NoExceptionExpected);
        }