diff --git a/Cargo.lock b/Cargo.lock
index 703d5ec..7098b88 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -852,6 +852,12 @@ version = "0.15.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1aaf95b3e5c8f23aa320147307562d361db0ae0d51242340f558153b4eb2439b"
 
+[[package]]
+name = "downcast"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1435fa1053d8b2fbbe9be7e97eca7f33d37b28409959813daefc1446a14247f1"
+
 [[package]]
 name = "dtoa"
 version = "1.0.10"
@@ -1000,6 +1006,12 @@ dependencies = [
  "percent-encoding",
 ]
 
+[[package]]
+name = "fragile"
+version = "2.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "28dd6caf6059519a65843af8fe2a3ae298b14b80179855aeb4adc2c1934ee619"
+
 [[package]]
 name = "frontend"
 version = "0.1.0"
@@ -1971,6 +1983,32 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
+[[package]]
+name = "mockall"
+version = "0.13.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39a6bfcc6c8c7eed5ee98b9c3e33adc726054389233e201c95dab2d41a3839d2"
+dependencies = [
+ "cfg-if",
+ "downcast",
+ "fragile",
+ "mockall_derive",
+ "predicates",
+ "predicates-tree",
+]
+
+[[package]]
+name = "mockall_derive"
+version = "0.13.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "25ca3004c2efe9011bd4e461bd8256445052b9615405b4f7ea43fc8ca5c20898"
+dependencies = [
+ "cfg-if",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "new_debug_unreachable"
 version = "1.0.6"
@@ -2303,6 +2341,32 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "925383efa346730478fb4838dbe9137d2a47675ad789c546d150a6e1dd4ab31c"
 
+[[package]]
+name = "predicates"
+version = "3.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5d19ee57562043d37e82899fade9a22ebab7be9cef5026b07fda9cdd4293573"
+dependencies = [
+ "anstyle",
+ "predicates-core",
+]
+
+[[package]]
+name = "predicates-core"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "727e462b119fe9c93fd0eb1429a5f7647394014cf3c04ab2c0350eeb09095ffa"
+
+[[package]]
+name = "predicates-tree"
+version = "1.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72dd2d6d381dfb73a193c7fca536518d7caee39fc8503f74e7dc0be0531b425c"
+dependencies = [
+ "predicates-core",
+ "termtree",
+]
+
 [[package]]
 name = "pretty_assertions"
 version = "1.4.1"
@@ -2464,6 +2528,7 @@ dependencies = [
  "cookie",
  "itertools",
  "lettre",
+ "mockall",
  "rand 0.9.1",
  "rand_core 0.9.3",
  "ron",
@@ -3308,6 +3373,12 @@ dependencies = [
  "windows-sys 0.59.0",
 ]
 
+[[package]]
+name = "termtree"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f50febec83f5ee1df3015341d8bd429f2d1cc62bcba7ea2076759d315084683"
+
 [[package]]
 name = "thiserror"
 version = "1.0.69"
diff --git a/backend/Cargo.toml b/backend/Cargo.toml
index 7486cf3..48f85b1 100644
--- a/backend/Cargo.toml
+++ b/backend/Cargo.toml
@@ -56,3 +56,4 @@ thiserror = "2"
 axum-test = "17"
 cookie = "0.18"
 scraper = "0.23"
+mockall = "0.13"
diff --git a/backend/tests/http.rs b/backend/tests/http.rs
index 7db1e7c..2b3e56a 100644
--- a/backend/tests/http.rs
+++ b/backend/tests/http.rs
@@ -1,10 +1,11 @@
-use std::error::Error;
+use std::{error::Error, sync::Arc};
 
 use axum_test::TestServer;
 use cookie::Cookie;
+use mockall::predicate;
 use scraper::{ElementRef, Html, Selector};
 
-use recipes::app;
+use recipes::{app, email};
 use serde::Serialize;
 
 mod utils;
@@ -104,7 +105,18 @@ pub struct SignUpFormData {
 #[tokio::test]
 async fn sign_up() -> Result<(), Box<dyn Error>> {
     // Arrange.
-    let state = utils::common_state().await?;
+    let mut mock_email_service = utils::mock_email::MockEmailService::new();
+    mock_email_service
+        .expect_send_email()
+        .with(
+            predicate::eq("president@spaceball.planet"),
+            predicate::always(),
+            predicate::always(),
+        )
+        .times(1)
+        .returning(|_email, _title, _message| Ok(()));
+
+    let state = utils::common_state_with_email_service(Arc::new(mock_email_service)).await?;
     let server = TestServer::new(app::make_service(state))?;
 
     // Act.
@@ -122,7 +134,6 @@ async fn sign_up() -> Result<(), Box<dyn Error>> {
 
     let document = Html::parse_document(&response.text());
     assert_eq!(document.errors.len(), 0);
-    dbg!(response);
 
     Ok(())
 }
diff --git a/backend/tests/utils/mock_email.rs b/backend/tests/utils/mock_email.rs
index 0f5e074..5e9debe 100644
--- a/backend/tests/utils/mock_email.rs
+++ b/backend/tests/utils/mock_email.rs
@@ -1,23 +1,20 @@
 use std::sync::Arc;
 
-use recipes::email;
+use async_trait::async_trait;
+use mockall::{mock, predicate::*};
 
-pub struct MockEmailService;
+use crate::email;
 
-impl MockEmailService {
-    pub fn create_service() -> Arc<dyn email::EmailServiceTrait> {
-        Arc::new(Self {})
+mock! {
+    pub EmailService {}
+    #[async_trait]
+    impl email::EmailServiceTrait for EmailService {
+        async fn send_email(&self, email: &str, title: &str, message: &str)
+            -> Result<(), email::Error>;
     }
 }
 
-#[async_trait::async_trait]
-impl email::EmailServiceTrait for MockEmailService {
-    async fn send_email(
-        &self,
-        _email: &str,
-        _title: &str,
-        _message: &str,
-    ) -> Result<(), email::Error> {
-        Ok(())
-    }
+// Default email service: will crash if `send_email` method is called.
+pub fn new_mock_email_service() -> Arc<dyn email::EmailServiceTrait> {
+    Arc::new(MockEmailService::new())
 }
diff --git a/backend/tests/utils/mod.rs b/backend/tests/utils/mod.rs
index 213fef4..3c209ab 100644
--- a/backend/tests/utils/mod.rs
+++ b/backend/tests/utils/mod.rs
@@ -1,10 +1,16 @@
-use std::error::Error;
+use std::{error::Error, sync::Arc};
 
-use recipes::{app, config, data::db, log};
+use recipes::{app, config, data::db, email, log};
 
-mod mock_email;
+pub mod mock_email;
 
 pub async fn common_state() -> Result<app::AppState, Box<dyn Error>> {
+    common_state_with_email_service(mock_email::new_mock_email_service()).await
+}
+
+pub async fn common_state_with_email_service(
+    email_service: Arc<dyn email::EmailServiceTrait>,
+) -> Result<app::AppState, Box<dyn Error>> {
     let db_connection = db::Connection::new_in_memory().await?;
     let config = config::Config::default();
     let log = log::Log::new_no_log();
@@ -12,7 +18,7 @@ pub async fn common_state() -> Result<app::AppState, Box<dyn Error>> {
         config,
         db_connection,
         log,
-        email_service: mock_email::MockEmailService::create_service(),
+        email_service,
     })
 }