implement Article.Json and its test

article.go

@@ -1,6 +1,10 @@
 package goscholar
 
-import "fmt"
+import (
+	"fmt"
+	"encoding/json"
+	log "github.com/Sirupsen/logrus"
+)
 
 type Article struct {
 	Title             *title
@@ -43,5 +47,9 @@ func (a *Article) String() string {
 }
 
 func (a *Article) Json() string {
-	return ""
+	bytes, err := json.Marshal(a)
+	if err != nil {
+		log.WithFields(log.Fields{"a": a, "err":err}).Error("Json encoding failed")
+	}
+	return string(bytes)
 }

article_test.go

@@ -4,6 +4,26 @@ import (
 	"testing"
 )
 
+var a *Article
+
+func init() {
+	a = &Article{
+		Title: &title{
+			Name: "Deep learning via Hessian-free optimization",
+			Url:  "http://machinelearning.wustl.edu/mlpapers/paper_files/icml2010_Martens10.pdf"},
+		Year:      "2010",
+		ClusterId: "15502119379559163003",
+		NumCite:   "260",
+		NumVer:    "9",
+		InfoId:    "e6RSJHGXItcJ",
+		Link: &link{
+			Name:   "wustl.edu",
+			Url:    "http://machinelearning.wustl.edu/mlpapers/paper_files/icml2010_Martens10.pdf",
+			Format: "PDF",
+		},
+	}
+}
+
 func TestString(t *testing.T) {
 	expected := `-----------------------------------------------------------------------------
 [Title]
@@ -25,25 +45,15 @@ func TestString(t *testing.T) {
   Format: PDF
 -----------------------------------------------------------------------------`
 
-	a := &Article{
-		Title: &title{
-			Name: "Deep learning via Hessian-free optimization",
-			Url:  "http://machinelearning.wustl.edu/mlpapers/paper_files/icml2010_Martens10.pdf"},
-		Year:      "2010",
-		ClusterId: "15502119379559163003",
-		NumCite:   "260",
-		NumVer:    "9",
-		InfoId:    "e6RSJHGXItcJ",
-		Link: &link{
-			Name:   "wustl.edu",
-			Url:    "http://machinelearning.wustl.edu/mlpapers/paper_files/icml2010_Martens10.pdf",
-			Format: "PDF",
-		},
-	}
-
 	if actual := a.String(); actual != expected {
 		t.Error(TestErr{expected:expected, actual:actual})
 	}
 }
 
-func TestJson(t *testing.T) {}
+func TestJson(t *testing.T) {
+	expected := `{"Title":{"Name":"Deep learning via Hessian-free optimization","Url":"http://machinelearning.wustl.edu/mlpapers/paper_files/icml2010_Martens10.pdf"},"Year":"2010","ClusterId":"15502119379559163003","NumCite":"260","NumVer":"9","InfoId":"e6RSJHGXItcJ","Link":{"Name":"wustl.edu","Url":"http://machinelearning.wustl.edu/mlpapers/paper_files/icml2010_Martens10.pdf","Format":"PDF"}}`
+
+	if actual := a.Json(); actual != expected {
+		t.Error(TestErr{expected:expected, actual:actual})
+	}
+}