added null checks to NewCarbonInterval

carboninterval.go

@@ -7,18 +7,25 @@ import (
 // CarbonInterval represents an interval between two carbons.
 type CarbonInterval struct {
 	Start *Carbon
-	End *Carbon
+	End   *Carbon
 }
 
 // NewCarbonInterval returns a pointer to a new CarbonInterval instance
 func NewCarbonInterval(start, end *Carbon) (*CarbonInterval, error) {
+	if start == nil {
+		return nil, errors.New("start date cannot be nil")
+	}
+	if end == nil {
+		return nil, errors.New("end date cannot be nil")
+	}
+
 	if start.Gte(end) {
-		return nil, errors.New("The end date must be greater than the start date.")
+		return nil, errors.New("the end date must be greater than or equal to the start date")
 	}
 
 	return &CarbonInterval{
 		Start: start,
-		End: end,
+		End:   end,
 	}, nil
 }
 

carboninterval_test.go

@@ -3,6 +3,7 @@ package carbon
 import (
 	"testing"
 	"time"
+
 	"github.com/stretchr/testify/assert"
 )
 
@@ -11,7 +12,7 @@ func TestErrorOnConstruction(t *testing.T) {
 	endDate, _ := Create(2009, time.November, 9, 23, 0, 0, 0, "UTC")
 
 	_, err := NewCarbonInterval(startDate, endDate)
-	assert.Error(t, err, "The end date must be greater than the start date.")
+	assert.Error(t, err, "the end date must be greater than or equal to the start date")
 }
 
 func TestDiffInHours(t *testing.T) {
@@ -21,3 +22,22 @@ func TestDiffInHours(t *testing.T) {
 	interval, _ := NewCarbonInterval(startDate, endDate)
 	assert.Equal(t, int64(1), interval.DiffInHours())
 }
+
+func TestErrorOnNilStartDate(t *testing.T) {
+	endDate, _ := Create(2009, time.November, 10, 24, 0, 0, 0, "UTC")
+
+	_, err := NewCarbonInterval(nil, endDate)
+	assert.Error(t, err, "start date cannot be nil")
+}
+
+func TestErrorOnNilEndDate(t *testing.T) {
+	startDate, _ := Create(2009, time.November, 10, 23, 0, 0, 0, "UTC")
+
+	_, err := NewCarbonInterval(startDate, nil)
+	assert.Error(t, err, "end date cannot be nil")
+}
+
+func TestErrorOnNilDates(t *testing.T) {
+	_, err := NewCarbonInterval(nil, nil)
+	assert.Error(t, err, "start date cannot be nil")
+}