test: add TestID_IsZero and improve doc comments

id.go

@@ -27,7 +27,7 @@
 //
 //   - Size: 12 bytes (96 bits), smaller than UUID, larger than snowflake
 //   - Base32 hex encoded by default (16 bytes storage when transported as printable string)
-//   - Non configured, you don't need set a unique machine and/or data center id
+//   - Non configured, you don't need to set a unique machine and/or data center id
 //   - K-ordered
 //   - Embedded time with 1 second precision
 //   - Unicity guaranteed for 16,777,216 (24 bits) unique ids per second and per host/process
@@ -362,12 +362,12 @@ func (id *ID) Scan(value interface{}) (err error) {
 	}
 }
 
-// IsNil Returns true if this is a "nil" ID
+// IsNil returns true if this is a "nil" ID
 func (id ID) IsNil() bool {
 	return id == nilID
 }
 
-// Alias of IsNil
+// IsZero returns true if this is a zero-value ID (alias of IsNil).
 func (id ID) IsZero() bool {
 	return id.IsNil()
 }

id_test.go

@@ -439,6 +439,39 @@ func TestID_IsNil(t *testing.T) {
 	}
 }
 
+func TestID_IsZero(t *testing.T) {
+	tests := []struct {
+		name string
+		id   ID
+		want bool
+	}{
+		{
+			name: "ID not zero",
+			id:   New(),
+			want: false,
+		},
+		{
+			name: "Zero ID",
+			id:   ID{},
+			want: true,
+		},
+		{
+			name: "NilID helper",
+			id:   NilID(),
+			want: true,
+		},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			if got, want := tt.id.IsZero(), tt.want; got != want {
+				t.Errorf("IsZero() = %v, want %v", got, want)
+			}
+		})
+	}
+}
+
+
 func TestNilID(t *testing.T) {
 	got := ID{}
 	if want := NilID(); !reflect.DeepEqual(got, want) {