Properly parses the template functions, and adds some tests

sample.tmpl

@@ -1 +1 @@
-¡Mañana es el cumpleaños de {{.Name}}! Puedes felicitarle o bien escribiendo a {{.Email}} o bien llamando al número {{.Phone}}
+¡Mañana es el cumpleaños de {{.Name}}! Cumple {{getYearsOld .YearOfBirth}} años, puedes felicitarle o bien escribiendo a {{.Email}} o bien llamando al número {{.Phone}}

server/helpers_test.go

@@ -31,7 +31,7 @@ func testConfig(t *testing.T) *model.Config {
 	return &model.Config{Birthdays: &model.BirthdaysConfig{File: f.Name()}}
 }
 
-func SetupTestHelper(t *testing.T) *TestHelper {
+func SetupTestHelper(t *testing.T, opts ...Option) *TestHelper {
 	th := &TestHelper{t: t}
 	th.ctrl = gomock.NewController(t)
 
@@ -54,14 +54,16 @@ func SetupTestHelper(t *testing.T) *TestHelper {
 		},
 	}
 
-	var err error
+	serverOpts := append([]Option{
-	th.srv, err = New(
 		WithConfig(testConfig(t)),
 		WithLogger(log.New(os.Stderr)),
 		WithBirthdays(birthdays),
 		WithNotificationServices(notificationServices),
 		WithWorkers(workers),
-	)
+	}, opts...)
+
+	var err error
+	th.srv, err = New(serverOpts...)
 	require.NoError(t, err)
 
 	th.srv.Start()

server/server.go

@@ -3,6 +3,7 @@ package server
 import (
 	"errors"
 	"fmt"
+	"path"
 	"text/template"
 	"time"
 
@@ -90,17 +91,20 @@ func New(options ...Option) (*Server, error) {
 	if srv.Config.Birthdays.Template != "" {
 		srv.Logger.Debug("parsing birthday template", "file", srv.Config.Birthdays.Template)
 
+		funcs := template.FuncMap{
+			"getYearsOld": func(yearOfBirth int) int {
+				return time.Now().Year() - yearOfBirth
+			},
+		}
+
 		var err error
-		srv.tmpl, err = template.ParseFiles(srv.Config.Birthdays.Template)
+		srv.tmpl, err = template.
+			New(path.Base(srv.Config.Birthdays.Template)).
+			Funcs(funcs).
+			ParseFiles(srv.Config.Birthdays.Template)
 		if err != nil {
 			return nil, fmt.Errorf("cannot parse template file %q: %w", srv.Config.Birthdays.Template, err)
 		}
-
-		srv.tmpl.Funcs(template.FuncMap{
-			"GetYearsOld": func(yearOfBirth int) int {
-				return time.Now().Year() - yearOfBirth
-			},
-		})
 	}
 
 	return srv, nil

server/server_test.go

@@ -1,9 +1,14 @@
 package server
 
 import (
+	"bytes"
 	"errors"
+	"fmt"
+	"os"
 	"testing"
+	"time"
 
+	"git.ctrlz.es/mgdelacroix/birthdaybot/model"
 	"github.com/stretchr/testify/require"
 )
 
@@ -35,3 +40,53 @@ func TestNotify(t *testing.T) {
 		require.ErrorIs(t, err, mockErr)
 	})
 }
+
+func TestTemplate(t *testing.T) {
+	t.Run("template should work with birthday data", func(t *testing.T) {
+		// create a template file and populate it
+		f, err := os.CreateTemp("", "birthdaybot-config-")
+		require.NoError(t, err)
+		_, werr := fmt.Fprint(f, "My name is {{.Name}}")
+		require.NoError(t, werr)
+		require.NoError(t, f.Close())
+
+		// create a test config and set the template
+		config := testConfig(t)
+		config.Birthdays.Template = f.Name()
+
+		// create the test helper with the custom config
+		th := SetupTestHelper(t, WithConfig(config))
+		defer th.TearDown()
+
+		birthday := &model.Birthday{Name: "Jane Doe"}
+		expectedString := "My name is Jane Doe"
+
+		var stringBuffer bytes.Buffer
+		require.NoError(t, th.srv.tmpl.Execute(&stringBuffer, birthday))
+		require.Equal(t, expectedString, stringBuffer.String())
+	})
+
+	t.Run("template should work with custom functions", func(t *testing.T) {
+		// create a template file and populate it
+		f, err := os.CreateTemp("", "birthdaybot-config-")
+		require.NoError(t, err)
+		_, werr := fmt.Fprint(f, "I'm getting {{getYearsOld .YearOfBirth}} years old")
+		require.NoError(t, werr)
+		require.NoError(t, f.Close())
+
+		// create a test config and set the template
+		config := testConfig(t)
+		config.Birthdays.Template = f.Name()
+
+		// create the test helper with the custom config
+		th := SetupTestHelper(t, WithConfig(config))
+		defer th.TearDown()
+
+		birthday := &model.Birthday{YearOfBirth: 1980}
+		expectedString := fmt.Sprintf("I'm getting %d years old", time.Now().Year()-birthday.YearOfBirth)
+
+		var stringBuffer bytes.Buffer
+		require.NoError(t, th.srv.tmpl.Execute(&stringBuffer, birthday))
+		require.Equal(t, expectedString, stringBuffer.String())
+	})
+}