test(json): add missing MarshalJSON empty queue path test

Author: bradub

blocking.go

@@ -2,7 +2,6 @@ package queue
 
 import (
 	"encoding/json"
-	"fmt"
 	"sync"
 )
 
@@ -286,11 +285,5 @@ func (bq *Blocking[T]) MarshalJSON() ([]byte, error) {
 		return []byte("[]"), nil
 	}
 
-	// Marshal the slice of elements into JSON.
-	data, err := json.Marshal(bq.elems)
-	if err != nil {
-		return nil, fmt.Errorf("failed to marshal blocking queue: %w", err)
-	}
-
-	return data, nil
+	return json.Marshal(bq.elems)
 }

blocking_test.go

@@ -710,22 +710,66 @@ func TestBlocking(t *testing.T) {
 	t.Run("MarshalJSON", func(t *testing.T) {
 		t.Parallel()
 
-		elems := []int{3, 2, 1}
+		t.Run("HasElements", func(t *testing.T) {
+			t.Parallel()
 
-		q := queue.NewBlocking(elems)
+			elems := []int{3, 2, 1}
 
-		marshaled, err := json.Marshal(q)
-		if err != nil {
-			t.Fatalf("expected no error, got %v", err)
-		}
+			q := queue.NewBlocking(elems)
 
-		expectedMarshaled := []byte(`[3,2,1]`)
-		if !bytes.Equal(expectedMarshaled, marshaled) {
-			t.Fatalf("expected marshaled to be %s, got %s", expectedMarshaled, marshaled)
-		}
+			marshaled, err := json.Marshal(q)
+			if err != nil {
+				t.Fatalf("expected no error, got %v", err)
+			}
+
+			expectedMarshaled := []byte(`[3,2,1]`)
+			if !bytes.Equal(expectedMarshaled, marshaled) {
+				t.Fatalf("expected marshaled to be %s, got %s", expectedMarshaled, marshaled)
+			}
+		})
+
+		t.Run("FailMarshal", func(t *testing.T) {
+			t.Parallel()
+
+			q := queue.NewBlocking([]failMarshal{{}})
+
+			marshaled, err := json.Marshal(q)
+			if err == nil {
+				t.Fatalf("expected error, got nil")
+			}
+
+			if marshaled != nil {
+				t.Fatalf("expected marshaled to be nil, got %s", marshaled)
+			}
+		})
+
+		t.Run("Empty", func(t *testing.T) {
+			t.Parallel()
+
+			q := queue.NewBlocking[int](nil)
+
+			marshaled, err := json.Marshal(q)
+			if err != nil {
+				t.Fatalf("expected no error, got %v", err)
+			}
+
+			expectedMarshaled := []byte(`[]`)
+			if !bytes.Equal(expectedMarshaled, marshaled) {
+				t.Fatalf("expected marshaled to be %s, got %s", expectedMarshaled, marshaled)
+			}
+		})
 	})
 }
 
+// failMarshal is a helper to fail the json marshalling of the queues
+type failMarshal struct{}
+
+var errFailMarshal = errors.New("intentional marshal error")
+
+func (f failMarshal) MarshalJSON() ([]byte, error) {
+	return nil, errFailMarshal
+}
+
 func testResetOnMultipleRoutinesFunc[T comparable](
 	ids []T,
 	totalRoutines int,

circular_test.go

@@ -296,19 +296,39 @@ func TestCircular(t *testing.T) {
 	t.Run("MarshalJSON", func(t *testing.T) {
 		t.Parallel()
 
-		elems := []int{3, 2, 1}
+		t.Run("HasElements", func(t *testing.T) {
+			t.Parallel()
 
-		q := queue.NewCircular(elems, 4)
+			elems := []int{3, 2, 1}
 
-		marshaled, err := json.Marshal(q)
-		if err != nil {
-			t.Fatalf("expected no error, got %v", err)
-		}
+			q := queue.NewCircular(elems, 4)
 
-		expectedMarshaled := []byte(`[3,2,1]`)
-		if !bytes.Equal(expectedMarshaled, marshaled) {
-			t.Fatalf("expected marshaled to be %s, got %s", expectedMarshaled, marshaled)
-		}
+			marshaled, err := json.Marshal(q)
+			if err != nil {
+				t.Fatalf("expected no error, got %v", err)
+			}
+
+			expectedMarshaled := []byte(`[3,2,1]`)
+			if !bytes.Equal(expectedMarshaled, marshaled) {
+				t.Fatalf("expected marshaled to be %s, got %s", expectedMarshaled, marshaled)
+			}
+		})
+
+		t.Run("Empty", func(t *testing.T) {
+			t.Parallel()
+
+			q := queue.NewCircular[int](nil, 1)
+
+			marshaled, err := json.Marshal(q)
+			if err != nil {
+				t.Fatalf("expected no error, got %v", err)
+			}
+
+			expectedMarshaled := []byte(`[]`)
+			if !bytes.Equal(expectedMarshaled, marshaled) {
+				t.Fatalf("expected marshaled to be %s, got %s", expectedMarshaled, marshaled)
+			}
+		})
 	})
 }