pgtype/hstore_test.go: Add coverage for text protocol

The existing test registers pgtype.Hstore in the text map, then uses
the query modes that use the binary protocol. The existing test did
not use the text parsing code. Add a version of the test that uses
pgtype.Hstore as the input and output argument in all query modes,
and tests it without registering the codec.

pgtype/hstore_test.go

@@ -181,7 +181,34 @@ func TestHstoreCodec(t *testing.T) {
 
 	pgxtest.RunValueRoundTripTests(context.Background(), t, ctr, pgxtest.KnownOIDQueryExecModes, "hstore", tests)
 
-	// scan empty and NULL: should be different
+	// run the tests using pgtype.Hstore as input and output types, and test all query modes
+	for i := range tests {
+		var h pgtype.Hstore
+		switch typedParam := tests[i].Param.(type) {
+		case map[string]*string:
+			h = pgtype.Hstore(typedParam)
+		case map[string]string:
+			if typedParam != nil {
+				h = pgtype.Hstore{}
+				for k, v := range typedParam {
+					h[k] = fs(v)
+				}
+			}
+		}
+
+		tests[i].Param = h
+		tests[i].Result = &pgtype.Hstore{}
+		tests[i].Test = func(input any) bool {
+			return reflect.DeepEqual(input, h)
+		}
+	}
+	pgxtest.RunValueRoundTripTests(context.Background(), t, ctr, pgxtest.AllQueryExecModes, "hstore", tests)
+
+	// run the tests again without the codec registered: uses the text protocol
+	ctrWithoutCodec := defaultConnTestRunner
+	pgxtest.RunValueRoundTripTests(context.Background(), t, ctrWithoutCodec, pgxtest.AllQueryExecModes, "hstore", tests)
+
+	// scan empty and NULL: should be different in all query modes
 	pgxtest.RunWithQueryExecModes(context.Background(), t, ctr, pgxtest.AllQueryExecModes, func(ctx context.Context, t testing.TB, conn *pgx.Conn) {
 		h := pgtype.Hstore{"should_be_erased": nil}
 		err := conn.QueryRow(ctx, `select cast(null as hstore)`).Scan(&h)