Add real smtp tests

- Allow users to test the smtp mailer by sending themselves e-mails
- Add a protection to ensure that either the HTML or the Text body
  exists so we never send blank e-mails.
- Fix a bug where if the html body was blank, the mime section for it
  was still set and therefore gmail and (probably) other clients would
  show a blank e-mail instead of the content in the text e-mails.

.gitignore

@@ -25,4 +25,6 @@ _testmain.go
 *.out
 
 *.iml
-.idea
+.idea
+
+defaults/smtp_mailer_test.json

defaults/smtp_mailer.go

@@ -10,10 +10,14 @@ import (
 	"text/template"
 	"time"
 
+	"github.com/pkg/errors"
 	"github.com/volatiletech/authboss"
 )
 
 // NewSMTPMailer creates an SMTP Mailer to send emails with.
+// An example usage might be something like:
+//
+//   NewSMTPMailer("smtp.gmail.com", smtp.PlainAuth("", "admin@yoursite.com", "password", "smtp.gmail.com"))
 func NewSMTPMailer(server string, auth smtp.Auth) *SMTPMailer {
 	if len(server) == 0 {
 		panic("SMTP Mailer must be created with a server string.")
@@ -31,6 +35,10 @@ type SMTPMailer struct {
 
 // Send an e-mail
 func (s SMTPMailer) Send(ctx context.Context, mail authboss.Email) error {
+	if len(mail.TextBody) == 0 && len(mail.HTMLBody) == 0 {
+		return errors.New("refusing to send mail without text or html body")
+	}
+
 	buf := &bytes.Buffer{}
 
 	data := struct {
@@ -110,15 +118,19 @@ MIME-Version: 1.0
 Content-Type: multipart/alternative; boundary="==============={{.Boundary}}=="
 Content-Transfer-Encoding: 7bit
 
+{{if .Mail.TextBody -}}
 --==============={{.Boundary}}==
 Content-Type: text/plain; charset=UTF-8
 Content-Transfer-Encoding: 7bit
 
 {{.Mail.TextBody}}
+{{end -}}
+{{if .Mail.HTMLBody -}}
 --==============={{.Boundary}}==
 Content-Type: text/html; charset=UTF-8
 Content-Transfer-Encoding: 7bit
 
 {{.Mail.HTMLBody}}
+{{end -}}
 --==============={{.Boundary}}==--
 `))

defaults/smtp_mailer_test.go

@@ -1,9 +1,77 @@
 package defaults
 
-import "testing"
+import (
+	"context"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"net/smtp"
+	"testing"
+
+	"github.com/volatiletech/authboss"
+)
+
+var (
+	flagTestSMTPMailer = flag.Bool("test-smtp-mailer", false, "Test the smtp mailer")
+)
 
 func TestSMTPMailer(t *testing.T) {
-	t.Skip("must implement test against real smtp servers here")
+	t.Parallel()
+
+	if !*flagTestSMTPMailer {
+		t.Skip("SMTP Mailer Testing not enabled (-test-smtp-mailer flag)")
+	}
+
+	creds := struct {
+		Server   string `json:"server,omitempty"`
+		Port     int    `json:"port,omitempty"`
+		Email    string `json:"email,omitempty"`
+		Password string `json:"password,omitempty"`
+	}{}
+
+	b, err := ioutil.ReadFile("smtp_mailer_test.json")
+	if err != nil {
+		t.Fatal(`error reading file: "smtp_mailer_test.json`, err)
+	}
+
+	if err = json.Unmarshal(b, &creds); err != nil {
+		t.Fatal(err)
+	}
+
+	server := fmt.Sprintf("%s:%d", creds.Server, creds.Port)
+	mailer := NewSMTPMailer(server, smtp.PlainAuth("", creds.Email, creds.Password, creds.Server))
+
+	mail := authboss.Email{
+		From:    creds.Email,
+		To:      []string{creds.Email},
+		Subject: "Authboss Test SMTP Mailer",
+	}
+
+	txtOnly := mail
+	txtOnly.Subject += ": Text Content"
+	txtOnly.TextBody = "Authboss\nSMTP\nTest\nWith\nNewlines"
+
+	if err = mailer.Send(context.Background(), txtOnly); err != nil {
+		t.Error(err)
+	}
+
+	htmlOnly := mail
+	htmlOnly.Subject += ": HTML Content"
+	htmlOnly.HTMLBody = "Authboss<br>Test<br>\nWith<br>Newlines\nand<br>breaks"
+
+	if err = mailer.Send(context.Background(), htmlOnly); err != nil {
+		t.Error(err)
+	}
+
+	mixed := mail
+	mixed.Subject += ": Mixed Content"
+	mixed.HTMLBody = htmlOnly.HTMLBody
+	mixed.TextBody = txtOnly.TextBody
+
+	if err = mailer.Send(context.Background(), mixed); err != nil {
+		t.Error(err)
+	}
 }
 
 func TestSMTPMailerPanic(t *testing.T) {