add test for respond func

api/api.go

@@ -20,7 +20,8 @@ type envelope struct {
 func respond(w http.ResponseWriter, d interface{}) {
 	w.Header().Set("Content-Type", "application/json")
 	enc := json.NewEncoder(w)
-	enc.Encode(d)
+	err := enc.Encode(d)
+	checkError(err)
 }
 
 // log fatal errors

api/api_test.go

@@ -1,7 +1,9 @@
 package api
 
 import (
+	"encoding/json"
 	"net/http"
+	"net/http/httptest"
 	"testing"
 )
 
@@ -62,3 +64,21 @@ func TestParseMajorMinor(t *testing.T) {
 		t.Errorf("Return value should be %s is %s instead", expected, actual)
 	}
 }
+
+func TestRespond(t *testing.T) {
+	w := httptest.NewRecorder()
+	respond(w, 15)
+
+	// assert json header
+	if w.Header().Get("Content-Type") != "application/json" {
+		t.Errorf("Invalid Content-Type header")
+	}
+
+	// assert json response
+	var d int
+	err := json.NewDecoder(w.Body).Decode(&d)
+	if err != nil {
+		t.Errorf("Invalid response body: %s", err)
+	}
+
+}