4 files changed, 125 insertions, 26 deletions
diff --git a/internal/feed/dataformat.go b/internal/feed/dataformat.go
new file mode 100644
index 0000000..bb3f8f8
--- /dev/null
+++ b/internal/feed/dataformat.go
@@ -0,0 +1,36 @@
+package feed
+
+//go:generate stringer -linecomment -type=DataFormat
+
+import (
+  "encoding/json"
+  "fmt"
+)
+
+// Data format for NVD feeds and feed items.
+type DataFormat byte
+
+const (
+  MitreFormat DataFormat = iota // MITRE
+)
+
+// Unmarshal DataFormat from JSON.
+func (me *DataFormat) UnmarshalJSON(b []byte) error {
+  // decode string, check for error
+  var s string
+  if err := json.Unmarshal(b, &s); err != nil {
+    return err
+  }
+
+  // check value
+  switch s {
+  case "MITRE":
+    *me = MitreFormat
+  default:
+    // return error
+    return fmt.Errorf("unknown data format: %s", s)
+  }
+
+  // return success
+  return nil
+}
diff --git a/internal/feed/dataformat_string.go b/internal/feed/dataformat_string.go
new file mode 100644
index 0000000..4b755f4
--- /dev/null
+++ b/internal/feed/dataformat_string.go
@@ -0,0 +1,23 @@
+// Code generated by "stringer -linecomment -type=DataFormat"; DO NOT EDIT.
+
+package feed
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[MitreFormat-0]
+}
+
+const _DataFormat_name = "MITRE"
+
+var _DataFormat_index = [...]uint8{0, 5}
+
+func (i DataFormat) String() string {
+	if i >= DataFormat(len(_DataFormat_index)-1) {
+		return "DataFormat(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _DataFormat_name[_DataFormat_index[i]:_DataFormat_index[i+1]]
+}
diff --git a/internal/feed/dataformat_test.go b/internal/feed/dataformat_test.go
new file mode 100644
index 0000000..efb4986
--- /dev/null
+++ b/internal/feed/dataformat_test.go
@@ -0,0 +1,65 @@
+package feed
+
+import (
+  "encoding/json"
+  "testing"
+)
+
+func TestDataFormatUnmarshalInvalidData(t *testing.T) {
+  test := []byte(`{}`)
+  var val DataFormat
+
+  if err := json.Unmarshal(test, &val); err == nil {
+    t.Errorf("got \"%s\", exp error", val)
+  }
+}
+
+func TestDataFormatUnmarshalUnknown(t *testing.T) {
+  test := []byte(`"foo"`)
+  exp := "unknown data format: foo"
+  var val DataFormat
+
+  err := json.Unmarshal(test, &val)
+  if err == nil {
+    t.Errorf("got \"%s\", exp error", val)
+    return
+  }
+
+  if err.Error() != exp {
+    t.Errorf("got \"%s\", exp \"%s\"", err.Error(), exp)
+  }
+}
+
+func TestDataFormatUnmarshalValid(t *testing.T) {
+  test := []byte(`"MITRE"`)
+  exp := MitreFormat
+  var got DataFormat
+
+  if err := json.Unmarshal(test, &got); err != nil {
+    t.Error(err)
+    return
+  }
+
+  if got != exp {
+    t.Errorf("got \"%s\", exp \"%s\"", got, exp)
+  }
+}
+
+func TestDataFormatString(t *testing.T) {
+  tests := []struct {
+    val DataFormat
+    exp string
+  } {
+    { MitreFormat, "MITRE" },
+    { DataFormat(255), "DataFormat(255)" },
+  }
+
+  for _, test := range(tests) {
+    t.Run(test.val.String(), func(t *testing.T) {
+      got := test.val.String()
+      if got != test.exp {
+        t.Errorf("got \"%s\", exp \"%s\"", got, test.exp)
+      }
+    })
+  }
+}
diff --git a/internal/feed/feed.go b/internal/feed/feed.go
index b4d514b..a43b7e9 100644
--- a/internal/feed/feed.go
+++ b/internal/feed/feed.go
@@ -9,8 +9,7 @@ import (
 )
 
 const (
-  MitreFormat = iota    // MITRE data format
-  DataVersion40   // Version 4.0
+  DataVersion40 = iota // Version 4.0
 
   OrNodeOp        // OR operator
   AndNodeOp       // And operator
@@ -43,30 +42,6 @@ const (
 
 // TODO: parse cpe
 
-// Data format for NVD feeds and feed items.
-type DataFormat int
-
-// Unmarshal DataFormat from JSON.
-func (me *DataFormat) UnmarshalJSON(b []byte) error {
-  // decode string, check for error
-  var s string
-  if err := json.Unmarshal(b, &s); err != nil {
-    return err
-  }
-
-  // check value
-  switch s {
-  case "MITRE":
-    *me = MitreFormat
-  default:
-    // return error
-    return fmt.Errorf("unknown data format: %s", s)
-  }
-
-  // return success
-  return nil
-}
-
 // Data version for NVD feeds and feed items.
 type DataVersion int