doc: explain how to use enum types properly (#4137)

examples/domaintypes/example_test.go

@@ -0,0 +1,47 @@
+// Copyright 2019-present Facebook Inc. All rights reserved.
+// This source code is licensed under the Apache 2.0 license found
+// in the LICENSE file in the root directory of this source tree.
+
+package main
+
+import (
+	"context"
+	"log"
+	"os"
+	"testing"
+
+	"ariga.io/atlas-go-sdk/atlasexec"
+	"entgo.io/ent/dialect"
+	"entgo.io/ent/examples/domaintypes/ent"
+	_ "github.com/lib/pq"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDomainTypes(t *testing.T) {
+	if os.Getenv("CI") != "" {
+		t.Skip()
+	}
+	ctx := context.Background()
+	client, err := ent.Open(dialect.Postgres, "postgres://postgres:pass@:5429/dev?search_path=public&sslmode=disable")
+	if err != nil {
+		log.Fatalln(err)
+	}
+	ac, err := atlasexec.NewClient(".", "atlas")
+	if err != nil {
+		log.Fatalf("failed to initialize client: %v", err)
+	}
+	// Automatically update the database with the desired schema.
+	// Another option, is to use 'migrate apply' or 'schema apply' manually.
+	_, err = ac.SchemaApply(ctx, &atlasexec.SchemaApplyParams{
+		// URL to your database. For example:
+		// postgres://postgres:pass@localhost:5432/database?search_path=public&sslmode=disable
+		URL: os.Getenv("DB_URL"),
+		Env: "local",
+	})
+	require.NoError(t, err)
+	t.Cleanup(func() { client.User.Delete().ExecX(ctx) })
+	err = client.User.Create().SetPostalCode("foo").Exec(ctx)
+	require.EqualError(t, err, `pq: value for domain us_postal_code violates check constraint "us_postal_code_check"`)
+	err = client.User.Create().SetPostalCode("12345").Exec(ctx)
+	require.NoError(t, err)
+}