Add 'now' function and function tests

Signed-off-by: Knut Ahlers <knut@ahlers.me>

Makefile

@@ -1,3 +1,6 @@
-ci:
+ci: test
 	curl -sSLo golang.sh https://raw.githubusercontent.com/Luzifer/github-publish/master/golang.sh
 	bash golang.sh
+
+test:
+	go test -v ./functions

functions/func_now.go

@@ -0,0 +1,9 @@
+package functions
+
+import "time"
+
+func init() {
+	registerFunction("now", func(name string, v ...string) string {
+		return time.Now().Format(name)
+	})
+}

functions/func_test.go

@@ -0,0 +1,77 @@
+package functions
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"math/rand"
+	"os"
+	"testing"
+	"text/template"
+	"time"
+)
+
+func renderHelper(tpl string, ctx map[string]interface{}) string {
+	t, err := template.New("mytemplate").Funcs(GetFunctionMap()).Parse(tpl)
+	if err != nil {
+		panic(err)
+	}
+
+	buf := bytes.NewBufferString("")
+	if err := t.Execute(buf, ctx); err != nil {
+		panic(err)
+	}
+
+	return buf.String()
+}
+
+func randomString() string {
+	const chars = "abcdefghijklmnopqrstuvwxyz0123456789"
+	r := rand.New(rand.NewSource(time.Now().UnixNano()))
+
+	result := make([]byte, 32)
+	for i := range result {
+		result[i] = chars[r.Intn(len(chars))]
+	}
+
+	return string(result)
+}
+
+func Test_GetFunctionMap(t *testing.T) {
+	f := GetFunctionMap()
+	if f == nil || len(f) < 1 {
+		t.Fatal("No functions were registered.")
+	}
+}
+
+func Test_env(t *testing.T) {
+	result := randomString()
+	os.Setenv("KORVIKE_TESTING", result)
+
+	if r := renderHelper(`{{env "KORVIKE_TESTING"}}`, nil); r != result {
+		t.Errorf("[env] did not receive expected string: %q (expected %q)", r, result)
+	}
+}
+
+func Test_file(t *testing.T) {
+	f, err := ioutil.TempFile("", "")
+	if err != nil {
+		panic(err)
+	}
+
+	p := f.Name()
+	result := randomString()
+	fmt.Fprint(f, result)
+	f.Close()
+	defer os.Remove(p)
+
+	if r := renderHelper(fmt.Sprintf("{{file %q}}", p), nil); r != result {
+		t.Errorf("[file] did not receive expected string: %q (expected %q)", r, result)
+	}
+}
+
+func Test_now(t *testing.T) {
+	if _, err := time.Parse(time.RFC3339Nano, renderHelper(fmt.Sprintf("{{now %q}}", time.RFC3339Nano), nil)); err != nil {
+		t.Errorf("[now] did not produce expected time format")
+	}
+}