Feedtag test (#265) [skip ci]

* FeedTag & Hashtag: update decoding flow

* FeedTag: add tests

* Contributing: add process for launching tests

Author: sviande

CONTRIBUTING.md

@@ -6,3 +6,30 @@ If you want to contribute to Goinsta API you must follow a simple instructions.
 
 - **Test your code after making pull request**. The title says it all.
 - **Include jokes if you can**. This instruction is optional.
+
+# Tests
+
+You need at least one goinsta exported object
+```
+package main
+
+import (
+	"fmt"
+	"github.com/ahmdrz/goinsta/v2"
+	"github.com/ahmdrz/goinsta/v2/utilities"
+)
+
+func main() {
+	inst := goinsta.New("user", "password")
+	err := inst.Login()
+	if err != nil {
+		fmt.Fatal(err)
+	}
+	fmt.Print(utilities.ExportAsBase64String(inst))
+}
+```
+
+Then you can use the output generated above to run your tests in the cli
+```
+INSTAGRAM_BASE64_USERNAME=BASE64_OUTPUT go test ./...
+```

feeds.go

@@ -131,10 +131,10 @@ func (ft *FeedTag) Next() bool {
 		},
 	)
 	if err == nil {
-		newFT := FeedTag{}
-		err = json.Unmarshal(body, &newFT)
+		newFT := &FeedTag{}
+		err = json.Unmarshal(body, newFT)
 		if err == nil {
-			*ft = newFT
+			*ft = *newFT
 			ft.inst = insta
 			ft.name = name
 			if !ft.MoreAvailable {

hashtags.go

@@ -101,10 +101,10 @@ func (h *Hashtag) Next() bool {
 		},
 	)
 	if err == nil {
-		ht := Hashtag{}
-		err = json.Unmarshal(body, &ht)
+		ht := &Hashtag{}
+		err = json.Unmarshal(body, ht)
 		if err == nil {
-			*h = ht
+			*h = *ht
 			h.inst = insta
 			h.Name = name
 			if !h.MoreAvailable {

tests/feed_test.go

@@ -29,3 +29,33 @@ func TestFeedTagLike(t *testing.T) {
 		t.Logf("media %s liked by goinsta", item.ID)
 	}
 }
+
+func TestFeedTagNext(t *testing.T) {
+	insta, err := getRandomAccount()
+	if err != nil {
+		t.Fatal(err)
+		return
+	}
+	feedTag, err := insta.Feed.Tags("golang")
+	if err != nil {
+		t.Fatal(err)
+		return
+	}
+
+	initNextID := feedTag.NextID
+	success := feedTag.Next()
+	if !success {
+		t.Fatal("Failed to fetch next page")
+		return
+	}
+	gotStatus := feedTag.Status
+
+	if gotStatus != "ok" {
+		t.Errorf("Status = %s; want ok", gotStatus)
+	}
+
+	gotNextID := feedTag.NextID
+	if gotNextID == initNextID {
+		t.Errorf("NextID must differ after FeedTag.Next() call")
+	}
+}