diff --git a/helpers/general.go b/helpers/general.go
index e0fe99b6f..a0aa20c78 100644
--- a/helpers/general.go
+++ b/helpers/general.go
@@ -75,6 +75,9 @@ func GuessType(in string) string {
 // ReaderToBytes takes an io.Reader argument, reads from it
 // and returns bytes.
 func ReaderToBytes(lines io.Reader) []byte {
+	if lines == nil {
+		return []byte{}
+	}
 	b := bp.GetBuffer()
 	defer bp.PutBuffer(b)
 
@@ -87,6 +90,9 @@ func ReaderToBytes(lines io.Reader) []byte {
 
 // ReaderToString is the same as ReaderToBytes, but returns a string.
 func ReaderToString(lines io.Reader) string {
+	if lines == nil {
+		return ""
+	}
 	b := bp.GetBuffer()
 	defer bp.PutBuffer(b)
 	b.ReadFrom(lines)
diff --git a/source/file_test.go b/source/file_test.go
new file mode 100644
index 000000000..6a4e456c6
--- /dev/null
+++ b/source/file_test.go
@@ -0,0 +1,25 @@
+package source
+
+import (
+	"github.com/spf13/hugo/helpers"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestFileUniqueID(t *testing.T) {
+	f1 := File{uniqueID: "123"}
+	f2 := NewFile("a")
+
+	assert.Equal(t, "123", f1.UniqueID())
+	assert.Equal(t, "0cc175b9c0f1b6a831c399e269772661", f2.UniqueID())
+}
+
+func TestFileString(t *testing.T) {
+	assert.Equal(t, "abc", NewFileWithContents("a", helpers.StringToReader("abc")).String())
+	assert.Equal(t, "", NewFile("a").String())
+}
+
+func TestFileBytes(t *testing.T) {
+	assert.Equal(t, []byte("abc"), NewFileWithContents("a", helpers.StringToReader("abc")).Bytes())
+	assert.Equal(t, []byte(""), NewFile("a").Bytes())
+}