Testing REST APIs in Go: A Guide to Unit and Integration Testing with Go&#s Standard Testing Library

// store.go
package user

import (
    "errors"
    "finance-crud-app/internal/types"
    "fmt"
    "log"

    "github.com/jmoiron/sqlx"
)

var (
    CreateUserError   = errors.New("cannot create user")
    RetrieveUserError = errors.New("cannot retrieve user")
    DeleteUserError   = errors.New("cannot delete user")
)

type Store struct {
    db *sqlx.DB
}

func NewStore(db *sqlx.DB) *Store {
    return &Store{db: db}
}

func (s *Store) CreateUser(user types.User) (user_id int, err error) {
    query := `
    INSERT INTO users
    (firstName, lastName, email, password)
    VALUES (, , , )
    RETURNING id`

    var userId int
    err = s.db.QueryRow(query, user.FirstName, user.LastName, user.Email, user.Password).Scan(&userId)
    if err != nil {
        return -1, CreateUserError
    }

    return userId, nil
}

func (s *Store) GetUserByEmail(email string) (types.User, error) {
    var user types.User

    err := s.db.Get(&user, "SELECT * FROM users WHERE email = ", email)
    if err != nil {
        return types.User{}, RetrieveUserError
    }

    if user.ID == 0 {
        log.Fatalf("user not found")
        return types.User{}, RetrieveUserError
    }

    return user, nil
}

func (s *Store) GetUserByID(id int) (*types.User, error) {
    var user types.User
    err := s.db.Get(&user, "SELECT * FROM users WHERE id = ", id)
    if err != nil {
        return nil, RetrieveUserError
    }

    if user.ID == 0 {
        return nil, fmt.Errorf("user not found")
    }

    return &user, nil
}

func (s *Store) DeleteUser(email string) error {

    user, err := s.GetUserByEmail(email)
    if err != nil {
        return DeleteUserError
    }
    // delete user records first
    _, err = s.db.Exec("DELETE FROM records WHERE userid = ", user.ID)
    if err != nil {
        return DeleteUserError
    }

    _, err = s.db.Exec("DELETE FROM users WHERE email = ", email)
    if err != nil {
        return DeleteUserError
    }
    return nil
}

// store_test.go

package user_test

import (
    "finance-crud-app/internal/db"
    "finance-crud-app/internal/services/user"
    "finance-crud-app/internal/types"
    "log"
    "os"
    "testing"

    "github.com/jmoiron/sqlx"
    _ "github.com/lib/pq"
)

var (
    userTestStore *user.Store
    testDB        *sqlx.DB
)

func TestMain(m *testing.M) {
    // database
    ConnStr := "postgres://postgres:Password123@localhost:5432/crud_db?sslmode=disable"
    testDB, err := db.NewPGStorage(ConnStr)
    if err != nil {
        log.Fatalf("could not connect %v", err)
    }
    defer testDB.Close()
    userTestStore = user.NewStore(testDB)

    code := m.Run()
    os.Exit(code)
}

func TestCreateUser(t *testing.T) {
    test_data := map[string]struct {
        user   types.User
        result any
    }{
        "should PASS valid user email used": {
            user: types.User{
                FirstName: "testfirsjjlkjt-1",
                LastName:  "testlastkjh-1",
                Email:     "validuser@email.com",
                Password:  "00000000",
            },
            result: nil,
        },
        "should FAIL invalid user email used": {
            user: types.User{
                FirstName: "testFirstName1",
                LastName:  "testLastName1",
                Email:     "test1@email.com",
                Password:  "800890",
            },
            result: user.CreateUserError,
        },
    }

    for name, tc := range test_data {
        t.Run(name, func(t *testing.T) {
            value, got := userTestStore.CreateUser(tc.user)
            if got != tc.result {
                t.Errorf("test fail expected %v got %v instead and value %v", tc.result, got, value)
            }
        })
    }

    t.Cleanup(func() {
        err := userTestStore.DeleteUser("validuser@email.com")
        if err != nil {
            t.Errorf("could not delete user %v got error %v", "validuser@email.com", err)
        }
    })
}

func TestGetUserByEmail(t *testing.T) {
    test_data := map[string]struct {
        email  string
        result any
    }{
        "should pass valid user email address used": {
            email:  "test1@email.com",
            result: nil,
        },
        "should fail invalid user email address used": {
            email:  "validuser@email.com",
            result: user.RetrieveUserError,
        },
    }

    for name, tc := range test_data {
        got, err := userTestStore.GetUserByEmail(tc.email)
        if err != tc.result {
            t.Errorf("test fail expected %v instead got %v", name, got)
        }
    }
}

func TestGetUserById(t *testing.T) {
    testUserId, err := userTestStore.CreateUser(types.User{
        FirstName: "userbyid",
        LastName:  "userbylast",
        Email:     "unique_email",
        Password:  "unique_password",
    })
    if err != nil {
        log.Panicf("got %v when creating testuser", testUserId)
    }

    test_data := map[string]struct {
        user_id int
        result  any
    }{
        "should pass valid user id used": {
            user_id: testUserId,
            result:  nil,
        },
        "should fail invalid user id used": {
            user_id: 0,
            result:  user.RetrieveUserError,
        },
    }

    for name, tc := range test_data {
        t.Run(name, func(t *testing.T) {
            _, got := userTestStore.GetUserByID(tc.user_id)
            if got != tc.result {
                t.Errorf("error retrieving user by id got %v want %v", got, tc.result)
            }
        })
    }

    t.Cleanup(func() {
        err := userTestStore.DeleteUser("unique_email")
        if err != nil {
            t.Errorf("could not delete user %v got error %v", "unique_email", err)
        }
    })
}

func TestDeleteUser(t *testing.T) {
    testUserId, err := userTestStore.CreateUser(types.User{
        FirstName: "userbyid",
        LastName:  "userbylast",
        Email:     "delete_user@email.com",
        Password:  "unique_password",
    })
    if err != nil {
        log.Panicf("got %v when creating testuser", testUserId)
    }

    test_data := map[string]struct {
        user_email string
        result     error
    }{
        "should pass user email address used": {
            user_email: "delete_user@email.com",
            result:     nil,
        },
    }

    for name, tc := range test_data {
        t.Run(name, func(t *testing.T) {
            err = userTestStore.DeleteUser(tc.user_email)
            if err != tc.result {
                t.Errorf("error deletig user got %v instead of %v", err, tc.result)
            }
        })
    }

    t.Cleanup(func() {
        err := userTestStore.DeleteUser("delete_user@email.com")
        if err != nil {
            log.Printf("could not delete user %v got error %v", "delete_user@email.com", err)
        }
    })
}