diff --git a/cmd/web/handlers.go b/cmd/web/handlers.go
index 9534a56..a72a3b4 100644
--- a/cmd/web/handlers.go
+++ b/cmd/web/handlers.go
@@ -17,3 +17,7 @@ func (app *application) home(w http.ResponseWriter, r *http.Request) {
 func (app *application) notImplemented(w http.ResponseWriter, r *http.Request) {
 	views.ComingSoon("Coming Soon", app.newCommonData(r)).Render(r.Context(), w)
 }
+
+func ping(w http.ResponseWriter, r *http.Request) {
+	w.Write([]byte("OK"))
+}
diff --git a/cmd/web/handlers_guestbook_test.go b/cmd/web/handlers_guestbook_test.go
new file mode 100644
index 0000000..3faaa03
--- /dev/null
+++ b/cmd/web/handlers_guestbook_test.go
@@ -0,0 +1,60 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+
+	"git.32bit.cafe/32bitcafe/guestbook/internal/assert"
+)
+
+func TestPing(t *testing.T) {
+	app := newTestApplication(t)
+	ts := newTestServer(t, app.routes())
+	defer ts.Close()
+
+	code, _, body := ts.get(t, "/ping")
+
+	assert.Equal(t, code, http.StatusOK)
+	assert.Equal(t, body, "OK")
+}
+
+func TestGetGuestbookView(t *testing.T) {
+	app := newTestApplication(t)
+	ts := newTestServer(t, app.routes())
+	defer ts.Close()
+
+	tests := []struct {
+		name     string
+		urlPath  string
+		wantCode int
+		wantBody string
+	}{
+		{
+			name:     "Valid id",
+			urlPath:  fmt.Sprintf("/websites/%s/guestbook", shortIdToSlug(1)),
+			wantCode: http.StatusOK,
+			wantBody: "Guestbook for Example",
+		},
+		{
+			name:     "Non-existent ID",
+			urlPath:  fmt.Sprintf("/websites/%s/guestbook", shortIdToSlug(2)),
+			wantCode: http.StatusNotFound,
+		},
+		{
+			name:     "String ID",
+			urlPath:  "/websites/abcd/guestbook",
+			wantCode: http.StatusNotFound,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			code, _, body := ts.get(t, tt.urlPath)
+			assert.Equal(t, code, tt.wantCode)
+			if tt.wantBody != "" {
+				assert.StringContains(t, body, tt.wantBody)
+			}
+		})
+	}
+}
diff --git a/cmd/web/handlers_user_test.go b/cmd/web/handlers_user_test.go
new file mode 100644
index 0000000..8a97224
--- /dev/null
+++ b/cmd/web/handlers_user_test.go
@@ -0,0 +1,121 @@
+package main
+
+import (
+	"net/http"
+	"net/url"
+	"testing"
+
+	"git.32bit.cafe/32bitcafe/guestbook/internal/assert"
+)
+
+func TestUserSignup(t *testing.T) {
+	app := newTestApplication(t)
+	ts := newTestServer(t, app.routes())
+	defer ts.Close()
+
+	_, _, body := ts.get(t, "/users/register")
+	validCSRFToken := extractCSRFToken(t, body)
+
+	const (
+		validName     = "John"
+		validPassword = "validPassword"
+		validEmail    = "john@example.com"
+		formTag       = `<form action="/users/register" method="post">`
+	)
+
+	tests := []struct {
+		name         string
+		userName     string
+		userEmail    string
+		userPassword string
+		csrfToken    string
+		wantCode     int
+		wantFormTag  string
+	}{
+		{
+			name:         "Valid submission",
+			userName:     validName,
+			userEmail:    validEmail,
+			userPassword: validPassword,
+			csrfToken:    validCSRFToken,
+			wantCode:     http.StatusSeeOther,
+		},
+		{
+			name:         "Missing token",
+			userName:     validName,
+			userEmail:    validEmail,
+			userPassword: validPassword,
+			wantCode:     http.StatusBadRequest,
+		},
+		{
+			name:         "Empty name",
+			userName:     "",
+			userEmail:    validEmail,
+			userPassword: validPassword,
+			csrfToken:    validCSRFToken,
+			wantCode:     http.StatusUnprocessableEntity,
+			wantFormTag:  formTag,
+		},
+		{
+			name:         "Empty email",
+			userName:     validName,
+			userEmail:    "",
+			userPassword: validPassword,
+			csrfToken:    validCSRFToken,
+			wantCode:     http.StatusUnprocessableEntity,
+			wantFormTag:  formTag,
+		},
+		{
+			name:         "Empty password",
+			userName:     validName,
+			userEmail:    validEmail,
+			userPassword: "",
+			csrfToken:    validCSRFToken,
+			wantCode:     http.StatusUnprocessableEntity,
+			wantFormTag:  formTag,
+		},
+		{
+			name:         "Invalid email",
+			userName:     validName,
+			userEmail:    "asdfasdf",
+			userPassword: validPassword,
+			csrfToken:    validCSRFToken,
+			wantCode:     http.StatusUnprocessableEntity,
+			wantFormTag:  formTag,
+		},
+		{
+			name:         "Invalid password",
+			userName:     validName,
+			userEmail:    validEmail,
+			userPassword: "asdfasd",
+			csrfToken:    validCSRFToken,
+			wantCode:     http.StatusUnprocessableEntity,
+			wantFormTag:  formTag,
+		},
+		{
+			name:         "Duplicate email",
+			userName:     validName,
+			userEmail:    "dupe@example.com",
+			userPassword: validPassword,
+			csrfToken:    validCSRFToken,
+			wantCode:     http.StatusUnprocessableEntity,
+			wantFormTag:  formTag,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(*testing.T) {
+			form := url.Values{}
+			form.Add("username", tt.userName)
+			form.Add("email", tt.userEmail)
+			form.Add("password", tt.userPassword)
+			form.Add("csrf_token", tt.csrfToken)
+			code, _, body := ts.postForm(t, "/users/register", form)
+			assert.Equal(t, code, tt.wantCode)
+			if tt.wantFormTag != "" {
+				assert.StringContains(t, body, tt.wantFormTag)
+			}
+		})
+	}
+
+}
diff --git a/cmd/web/main.go b/cmd/web/main.go
index ba9115c..7f22d07 100644
--- a/cmd/web/main.go
+++ b/cmd/web/main.go
@@ -21,9 +21,9 @@ import (
 type application struct {
 	sequence          uint16
 	logger            *slog.Logger
-	websites          *models.WebsiteModel
-	users             *models.UserModel
-	guestbookComments *models.GuestbookCommentModel
+	websites          models.WebsiteModelInterface
+	users             models.UserModelInterface
+	guestbookComments models.GuestbookCommentModelInterface
 	sessionManager    *scs.SessionManager
 	formDecoder       *schema.Decoder
 	debug             bool
diff --git a/cmd/web/routes.go b/cmd/web/routes.go
index c2fe48a..31d0d41 100644
--- a/cmd/web/routes.go
+++ b/cmd/web/routes.go
@@ -11,6 +11,8 @@ func (app *application) routes() http.Handler {
 	mux := http.NewServeMux()
 	mux.Handle("GET /static/", http.FileServerFS(ui.Files))
 
+	mux.HandleFunc("GET /ping", ping)
+
 	dynamic := alice.New(app.sessionManager.LoadAndSave, noSurf, app.authenticate)
 	standard := alice.New(app.recoverPanic, app.logRequest, commonHeaders)
 
diff --git a/cmd/web/testutils_test.go b/cmd/web/testutils_test.go
new file mode 100644
index 0000000..b5267b6
--- /dev/null
+++ b/cmd/web/testutils_test.go
@@ -0,0 +1,96 @@
+package main
+
+import (
+	"bytes"
+	"html"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/http/cookiejar"
+	"net/http/httptest"
+	"net/url"
+	"regexp"
+	"testing"
+	"time"
+
+	"git.32bit.cafe/32bitcafe/guestbook/internal/models/mocks"
+	"github.com/alexedwards/scs/v2"
+	"github.com/gorilla/schema"
+)
+
+func newTestApplication(t *testing.T) *application {
+	formDecoder := schema.NewDecoder()
+	formDecoder.IgnoreUnknownKeys(true)
+
+	sessionManager := scs.New()
+	sessionManager.Lifetime = 12 * time.Hour
+	sessionManager.Cookie.Secure = true
+
+	return &application{
+		logger:            slog.New(slog.NewTextHandler(io.Discard, nil)),
+		sessionManager:    sessionManager,
+		websites:          &mocks.WebsiteModel{},
+		users:             &mocks.UserModel{},
+		guestbookComments: &mocks.GuestbookCommentModel{},
+		formDecoder:       formDecoder,
+		timezones:         getAvailableTimezones(),
+	}
+}
+
+type testServer struct {
+	*httptest.Server
+}
+
+func newTestServer(t *testing.T, h http.Handler) *testServer {
+	ts := httptest.NewTLSServer(h)
+	jar, err := cookiejar.New(nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	ts.Client().Jar = jar
+	ts.Client().CheckRedirect = func(req *http.Request, via []*http.Request) error {
+		return http.ErrUseLastResponse
+	}
+	return &testServer{ts}
+}
+
+func (ts *testServer) get(t *testing.T, urlPath string) (int, http.Header, string) {
+	rs, err := ts.Client().Get(ts.URL + urlPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer rs.Body.Close()
+	body, err := io.ReadAll(rs.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	body = bytes.TrimSpace(body)
+
+	return rs.StatusCode, rs.Header, string(body)
+}
+
+func (ts *testServer) postForm(t *testing.T, urlPath string, form url.Values) (int, http.Header, string) {
+	rs, err := ts.Client().PostForm(ts.URL+urlPath, form)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer rs.Body.Close()
+	body, err := io.ReadAll(rs.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	body = bytes.TrimSpace(body)
+	return rs.StatusCode, rs.Header, string(body)
+}
+
+var csrfTokenRX = regexp.MustCompile(`<input type="hidden" name="csrf_token" value="(.+?)">`)
+
+func extractCSRFToken(t *testing.T, body string) string {
+	matches := csrfTokenRX.FindStringSubmatch(body)
+	if len(matches) < 2 {
+		t.Fatal("no csrf token found in body")
+	}
+	return html.UnescapeString(matches[1])
+}
diff --git a/internal/assert/assert.go b/internal/assert/assert.go
new file mode 100644
index 0000000..5f6c938
--- /dev/null
+++ b/internal/assert/assert.go
@@ -0,0 +1,22 @@
+package assert
+
+import (
+	"strings"
+	"testing"
+)
+
+func Equal[T comparable](t *testing.T, actual, expected T) {
+	t.Helper()
+
+	if actual != expected {
+		t.Errorf("got: %v; want %v", actual, expected)
+	}
+}
+
+func StringContains(t *testing.T, actual, expectedSubstring string) {
+	t.Helper()
+
+	if !strings.Contains(actual, expectedSubstring) {
+		t.Errorf("got: %q; expected to contain: %q", actual, expectedSubstring)
+	}
+}
diff --git a/internal/models/guestbookcomment.go b/internal/models/guestbookcomment.go
index d071adf..4a7203b 100644
--- a/internal/models/guestbookcomment.go
+++ b/internal/models/guestbookcomment.go
@@ -24,6 +24,15 @@ type GuestbookCommentModel struct {
 	DB *sql.DB
 }
 
+type GuestbookCommentModelInterface interface {
+	Insert(shortId uint64, guestbookId, parentId int64, authorName, authorEmail, authorSite, commentText, pageUrl string, isPublished bool) (int64, error)
+	Get(shortId uint64) (GuestbookComment, error)
+	GetAll(guestbookId int64) ([]GuestbookComment, error)
+	GetDeleted(guestbookId int64) ([]GuestbookComment, error)
+	GetUnpublished(guestbookId int64) ([]GuestbookComment, error)
+	UpdateComment(comment *GuestbookComment) error
+}
+
 func (m *GuestbookCommentModel) Insert(shortId uint64, guestbookId, parentId int64, authorName,
 	authorEmail, authorSite, commentText, pageUrl string, isPublished bool) (int64, error) {
 	stmt := `INSERT INTO guestbook_comments (ShortId, GuestbookId, ParentId, AuthorName,
diff --git a/internal/models/mocks/guestbookcomment.go b/internal/models/mocks/guestbookcomment.go
new file mode 100644
index 0000000..6a0c972
--- /dev/null
+++ b/internal/models/mocks/guestbookcomment.go
@@ -0,0 +1,64 @@
+package mocks
+
+import (
+	"time"
+
+	"git.32bit.cafe/32bitcafe/guestbook/internal/models"
+)
+
+var mockGuestbookComment = models.GuestbookComment{
+	ID:          1,
+	ShortId:     1,
+	GuestbookId: 1,
+	AuthorName:  "John Test",
+	AuthorEmail: "test@example.com",
+	AuthorSite:  "example.com",
+	CommentText: "Hello, world",
+	Created:     time.Now(),
+	IsPublished: true,
+}
+
+type GuestbookCommentModel struct{}
+
+func (m *GuestbookCommentModel) Insert(shortId uint64, guestbookId, parentId int64, authorName,
+	authorEmail, authorSite, commentText, pageUrl string, isPublished bool) (int64, error) {
+	return 2, nil
+}
+
+func (m *GuestbookCommentModel) Get(shortId uint64) (models.GuestbookComment, error) {
+	switch shortId {
+	case 1:
+		return mockGuestbookComment, nil
+	default:
+		return models.GuestbookComment{}, models.ErrNoRecord
+	}
+}
+
+func (m *GuestbookCommentModel) GetAll(guestbookId int64) ([]models.GuestbookComment, error) {
+	switch guestbookId {
+	case 1:
+		return []models.GuestbookComment{mockGuestbookComment}, nil
+	case 2:
+		return []models.GuestbookComment{}, nil
+	default:
+		return []models.GuestbookComment{}, models.ErrNoRecord
+	}
+}
+
+func (m *GuestbookCommentModel) GetDeleted(guestbookId int64) ([]models.GuestbookComment, error) {
+	switch guestbookId {
+	default:
+		return []models.GuestbookComment{}, models.ErrNoRecord
+	}
+}
+
+func (m *GuestbookCommentModel) GetUnpublished(guestbookId int64) ([]models.GuestbookComment, error) {
+	switch guestbookId {
+	default:
+		return []models.GuestbookComment{}, models.ErrNoRecord
+	}
+}
+
+func (m *GuestbookCommentModel) UpdateComment(comment *models.GuestbookComment) error {
+	return nil
+}
diff --git a/internal/models/mocks/users.go b/internal/models/mocks/users.go
new file mode 100644
index 0000000..2e5ff45
--- /dev/null
+++ b/internal/models/mocks/users.go
@@ -0,0 +1,89 @@
+package mocks
+
+import (
+	"time"
+
+	"git.32bit.cafe/32bitcafe/guestbook/internal/models"
+)
+
+var mockUser = models.User{
+	ID:       1,
+	ShortId:  1,
+	Username: "tester",
+	Email:    "test@example.com",
+	Deleted:  false,
+	IsBanned: false,
+	Created:  time.Now(),
+	Settings: mockUserSettings,
+}
+
+var mockUserSettings = models.UserSettings{
+	LocalTimezone: time.UTC,
+}
+
+type UserModel struct {
+	Settings map[string]models.Setting
+}
+
+func (m *UserModel) InitializeSettingsMap() error {
+	return nil
+}
+
+func (m *UserModel) Insert(shortId uint64, username string, email string, password string, settings models.UserSettings) error {
+	switch email {
+	case "dupe@example.com":
+		return models.ErrDuplicateEmail
+	default:
+		return nil
+	}
+}
+
+func (m *UserModel) Get(shortId uint64) (models.User, error) {
+	switch shortId {
+	case 1:
+		return mockUser, nil
+	default:
+		return models.User{}, models.ErrNoRecord
+	}
+}
+
+func (m *UserModel) GetById(id int64) (models.User, error) {
+	switch id {
+	case 1:
+		return mockUser, nil
+	default:
+		return models.User{}, models.ErrNoRecord
+	}
+}
+
+func (m *UserModel) GetAll() ([]models.User, error) {
+	return []models.User{mockUser}, nil
+}
+
+func (m *UserModel) Authenticate(email, password string) (int64, error) {
+	if email == "test@example.com" && password == "password" {
+		return 1, nil
+	}
+	return 0, models.ErrInvalidCredentials
+}
+
+func (m *UserModel) Exists(id int64) (bool, error) {
+	switch id {
+	case 1:
+		return true, nil
+	default:
+		return false, nil
+	}
+}
+
+func (m *UserModel) GetSettings(userId int64) (models.UserSettings, error) {
+	return mockUserSettings, nil
+}
+
+func (m *UserModel) UpdateUserSettings(userId int64, settings models.UserSettings) error {
+	return nil
+}
+
+func (m *UserModel) UpdateSetting(userId int64, setting models.Setting, value string) error {
+	return nil
+}
diff --git a/internal/models/mocks/website.go b/internal/models/mocks/website.go
new file mode 100644
index 0000000..83cc69e
--- /dev/null
+++ b/internal/models/mocks/website.go
@@ -0,0 +1,77 @@
+package mocks
+
+import (
+	"time"
+
+	"git.32bit.cafe/32bitcafe/guestbook/internal/models"
+)
+
+var mockGuestbook = models.Guestbook{
+	ID:        1,
+	ShortId:   1,
+	UserId:    1,
+	WebsiteId: 1,
+	Created:   time.Now(),
+	IsActive:  true,
+	Settings: models.GuestbookSettings{
+		IsCommentingEnabled:   true,
+		IsVisible:             true,
+		FilteredWords:         make([]string, 0),
+		AllowRemoteHostAccess: true,
+	},
+}
+
+var mockWebsite = models.Website{
+	ID:         1,
+	ShortId:    1,
+	Name:       "Example",
+	SiteUrl:    "example.com",
+	AuthorName: "John Test",
+	UserId:     1,
+	Created:    time.Now(),
+	Guestbook:  mockGuestbook,
+}
+
+type WebsiteModel struct{}
+
+func (m *WebsiteModel) Insert(shortId uint64, userId int64, siteName, siteUrl, authorName string) (int64, error) {
+	return 2, nil
+}
+
+func (m *WebsiteModel) Get(shortId uint64) (models.Website, error) {
+	switch shortId {
+	case 1:
+		return mockWebsite, nil
+	default:
+		return models.Website{}, models.ErrNoRecord
+	}
+}
+
+func (m *WebsiteModel) GetAllUser(userId int64) ([]models.Website, error) {
+	return []models.Website{mockWebsite}, nil
+}
+
+func (m *WebsiteModel) GetById(id int64) (models.Website, error) {
+	switch id {
+	case 1:
+		return mockWebsite, nil
+	default:
+		return models.Website{}, models.ErrNoRecord
+	}
+}
+
+func (m *WebsiteModel) GetAll() ([]models.Website, error) {
+	return []models.Website{mockWebsite}, nil
+}
+
+func (m *WebsiteModel) InitializeSettingsMap() error {
+	return nil
+}
+
+func (m *WebsiteModel) UpdateGuestbookSettings(guestbookId int64, settings models.GuestbookSettings) error {
+	return nil
+}
+
+func (m *WebsiteModel) UpdateSetting(guestbookId int64, setting models.Setting, value string) error {
+	return nil
+}
diff --git a/internal/models/user.go b/internal/models/user.go
index acd9178..f7c5ab0 100644
--- a/internal/models/user.go
+++ b/internal/models/user.go
@@ -35,6 +35,18 @@ type UserModel struct {
 	Settings map[string]Setting
 }
 
+type UserModelInterface interface {
+	InitializeSettingsMap() error
+	Insert(shortId uint64, username string, email string, password string, settings UserSettings) error
+	Get(shortId uint64) (User, error)
+	GetById(id int64) (User, error)
+	GetAll() ([]User, error)
+	Authenticate(email, password string) (int64, error)
+	Exists(id int64) (bool, error)
+	UpdateUserSettings(userId int64, settings UserSettings) error
+	UpdateSetting(userId int64, setting Setting, value string) error
+}
+
 func (m *UserModel) InitializeSettingsMap() error {
 	if m.Settings == nil {
 		m.Settings = make(map[string]Setting)
diff --git a/internal/models/website.go b/internal/models/website.go
index 456c92d..53eb35d 100644
--- a/internal/models/website.go
+++ b/internal/models/website.go
@@ -90,6 +90,16 @@ func (m *WebsiteModel) InitializeSettingsMap() error {
 	return nil
 }
 
+type WebsiteModelInterface interface {
+	Insert(shortId uint64, userId int64, siteName, siteUrl, authorName string) (int64, error)
+	Get(shortId uint64) (Website, error)
+	GetAllUser(userId int64) ([]Website, error)
+	GetAll() ([]Website, error)
+	InitializeSettingsMap() error
+	UpdateGuestbookSettings(guestbookId int64, settings GuestbookSettings) error
+	UpdateSetting(guestbookId int64, setting Setting, value string) error
+}
+
 func (m *WebsiteModel) Insert(shortId uint64, userId int64, siteName, siteUrl, authorName string) (int64, error) {
 	stmt := `INSERT INTO websites (ShortId, Name, SiteUrl, AuthorName, UserId, Created)
 			VALUES (?, ?, ?, ?, ?, ?)`