diff --git a/config/parse/parse.go b/config/parse/parse.go
index 6695abdf..b44041d4 100644
--- a/config/parse/parse.go
+++ b/config/parse/parse.go
@@ -24,4 +24,6 @@ func allTokens(input io.Reader) (tokens []token) {
 	return
 }
 
+// Set of directives that are valid (unordered). Populated
+// by config package's init function.
 var ValidDirectives = make(map[string]struct{})
diff --git a/config/parse/parse_test.go b/config/parse/parse_test.go
new file mode 100644
index 00000000..48746300
--- /dev/null
+++ b/config/parse/parse_test.go
@@ -0,0 +1,22 @@
+package parse
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestAllTokens(t *testing.T) {
+	input := strings.NewReader("a b c\nd e")
+	expected := []string{"a", "b", "c", "d", "e"}
+	tokens := allTokens(input)
+
+	if len(tokens) != len(expected) {
+		t.Fatalf("Expected %d tokens, got %d", len(expected), len(tokens))
+	}
+
+	for i, val := range expected {
+		if tokens[i].text != val {
+			t.Errorf("Token %d should be '%s' but was '%s'", i, val, tokens[i].text)
+		}
+	}
+}