Assignment 4: add unit, integration, and e2e tests; refactor for testability

internal/store/user_store.go

@@ -2,11 +2,14 @@ package store
 
 import (
 	"context"
+	"errors"
 	"sync"
 
 	"5803025015/w04/internal/models"
+
 	"github.com/google/uuid"
 	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
 )
 
 type UserStore struct {
@@ -34,7 +37,14 @@ func (s *UserStore) Create(ctx context.Context, user *models.User) error {
 
 	query := `INSERT INTO users (id, username, password_hash) VALUES ($1, $2, $3)`
 	_, err := s.conn.Exec(ctx, query, user.ID, user.Username, user.PasswordHash)
-	return err
+	if err != nil {
+		var pgErr *pgconn.PgError
+		if errors.As(err, &pgErr) && pgErr.Code == "23505" {
+			return ErrDuplicate
+		}
+		return err
+	}
+	return nil
 }
 
 func (s *UserStore) GetByUsername(ctx context.Context, username string) (*models.User, error) {
@@ -45,6 +55,9 @@ func (s *UserStore) GetByUsername(ctx context.Context, username string) (*models
 	query := `SELECT id, username, password_hash FROM users WHERE username = $1`
 	err := s.conn.QueryRow(ctx, query, username).Scan(&u.ID, &u.Username, &u.PasswordHash)
 	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, ErrNotFound
+		}
 		return nil, err
 	}
 	return &u, nil
@@ -58,6 +71,9 @@ func (s *UserStore) GetByID(ctx context.Context, id string) (*models.User, error
 	query := `SELECT id, username, password_hash FROM users WHERE id = $1`
 	err := s.conn.QueryRow(ctx, query, id).Scan(&u.ID, &u.Username, &u.PasswordHash)
 	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, ErrNotFound
+		}
 		return nil, err
 	}
 	return &u, nil