Test internal/grammar, and allow the root to import it

internal/grammar/name_test.go

@@ -0,0 +1,16 @@
+package grammar
+
+import "testing"
+
+func TestCheckNameRefusesWhatAGrammarReserves(t *testing.T) {
+	for _, name := range []string{"", "-", "a as b", "a.b", "a|b", "a(b", "a{b", "a}b", "a/b", "a[b", "a]b", `a"b`} {
+		if CheckName(name) == nil {
+			t.Errorf("CheckName(%q) = nil, want an error", name)
+		}
+	}
+	for _, name := range []string{"a", "postal-code", "é", "a_b"} {
+		if err := CheckName(name); err != nil {
+			t.Errorf("CheckName(%q) = %v, want nil", name, err)
+		}
+	}
+}