diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index ad9291c..b6ae3e2 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -1,4 +1,4 @@
-name: Run unit tests
+name: CI
 
 on:
   push:
@@ -14,6 +14,8 @@ env:
   CARGO_TERM_COLOR: always
 
 jobs:
+  # Native tests
+
   test_app_sdk:
     name: Run V-App SDK tests
     runs-on: ubuntu-latest
@@ -109,3 +111,89 @@ jobs:
         working-directory: apps/test/client
         run: |
           cargo +nightly test --target x86_64-unknown-linux-gnu
+
+  # build Vanadium VM app
+
+  build_application:
+    name: Build application using the reusable workflow
+    uses: LedgerHQ/ledger-app-workflows/.github/workflows/reusable_build.yml@v1
+    with:
+      upload_app_binaries_artifact: "vanadium_binaries"
+      builder: ledger-app-builder
+
+  ### Risc-V tests
+
+  # build test V-App
+  build_vapp_test:
+    name: Build vnd-test on Risc-V target
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set up Rust toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          target: riscv32i-unknown-none-elf
+          components: rustfmt, clippy
+          profile: minimal
+      - name: Clone
+        uses: actions/checkout@v4
+      - name: Build app
+        working-directory: apps/test/app
+        run: |
+          cargo +nightly build --release --target riscv32i-unknown-none-elf
+      - name: Upload binaries
+        uses: actions/upload-artifact@v4
+        with:
+          name: vnd_test_riscv_binary
+          path: apps/test/app/target/riscv32i-unknown-none-elf/release/vnd-test
+
+  run_speculos_integration_tests:
+    name: Integration tests on Speculos
+
+    strategy:
+      matrix:
+        include:
+          # - model: nanox  # TODO: reenable once compilation is fixed
+          - model: nanosplus
+          - model: flex
+          - model: stax
+
+    runs-on: ubuntu-latest
+    needs: [build_application, build_vapp_test]
+    steps:
+      - name: Set up Rust toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          target: x86_64-unknown-linux-gnu
+          components: rustfmt, clippy
+          profile: minimal
+      - name: Install Speculos
+        run: |
+          pip install speculos
+      - name: Install dependencies
+        run: |
+          sudo apt-get update && \
+          sudo apt-get install -y libudev-dev pkg-config && \
+          sudo apt-get install -y qemu-user-static libvncserver-dev
+      - name: Clone
+        uses: actions/checkout@v4
+      - name: Download Vanadium binaries
+        uses: actions/download-artifact@v4
+        with:
+          name: vanadium_binaries
+          path: ./vanadium_binaries
+
+      - name: Download vnd_test_riscv_binary
+        uses: actions/download-artifact@v4
+        with:
+          name: vnd_test_riscv_binary
+          path: ./vnd_test_riscv_binary
+
+      - name: Run integration tests
+        working-directory: apps/test/client
+        env:
+          VANADIUM_BINARY: ../../../vanadium_binaries/${{ matrix.model }}/release/app-vanadium
+          VAPP_BINARY: ../../../vnd_test_riscv_binary/vnd-test
+        run: |
+          cargo test --features speculos-tests
\ No newline at end of file
diff --git a/app-sdk/src/bignum.rs b/app-sdk/src/bignum.rs
index c2f1009..dd063cd 100644
--- a/app-sdk/src/bignum.rs
+++ b/app-sdk/src/bignum.rs
@@ -192,7 +192,7 @@ impl<'a, const N: usize> BigNumMod<'a, N> {
         }
         // reduce the buffer my the modulus
         let mut buffer = buffer;
-        if !Ecall::bn_modm(
+        if 1 != Ecall::bn_modm(
             buffer.as_mut_ptr(),
             buffer.as_ptr(),
             N,
@@ -220,7 +220,7 @@ impl<'a, const N: usize> BigNumMod<'a, N> {
         let mut buffer = [0u8; N];
         buffer[N - 4..N].copy_from_slice(&value.to_be_bytes());
 
-        if !Ecall::bn_modm(
+        if 1 != Ecall::bn_modm(
             buffer.as_mut_ptr(),
             buffer.as_ptr(),
             N,
@@ -251,7 +251,7 @@ impl<'a, const N: usize> BigNumMod<'a, N> {
             self.modulus.m.as_ptr(),
             N,
         );
-        if !res {
+        if res != 1 {
             panic!("Exponentiation failed");
         }
         Self::from_be_bytes(result, self.modulus)
@@ -298,7 +298,7 @@ impl<'a, const N: usize> Add for &BigNumMod<'a, N> {
             self.modulus.m.as_ptr(),
             N,
         );
-        if !res {
+        if res != 1 {
             panic!("Addition failed");
         }
         BigNumMod::from_be_bytes(result, self.modulus)
@@ -318,7 +318,7 @@ impl<'a, const N: usize> AddAssign for BigNumMod<'a, N> {
             self.modulus.m.as_ptr(),
             N,
         );
-        if !res {
+        if res != 1 {
             panic!("Addition failed");
         }
     }
@@ -362,7 +362,7 @@ impl<'a, const N: usize> Sub for &BigNumMod<'a, N> {
             self.modulus.m.as_ptr(),
             N,
         );
-        if !res {
+        if res != 1 {
             panic!("Subtraction failed");
         }
         BigNumMod::from_be_bytes(result, self.modulus)
@@ -382,7 +382,7 @@ impl<'a, const N: usize> SubAssign for BigNumMod<'a, N> {
             self.modulus.m.as_ptr(),
             N,
         );
-        if !res {
+        if res != 1 {
             panic!("Subtraction failed");
         }
     }
@@ -418,7 +418,7 @@ impl<'a, const N: usize> core::ops::Mul for &BigNumMod<'a, N> {
             self.modulus.m.as_ptr(),
             N,
         );
-        if !res {
+        if res != 1 {
             panic!("Multiplication failed");
         }
         BigNumMod::from_be_bytes(result, self.modulus)
@@ -438,7 +438,7 @@ impl<'a, const N: usize> MulAssign<&Self> for BigNumMod<'a, N> {
             self.modulus.m.as_ptr(),
             N,
         );
-        if !res {
+        if res != 1 {
             panic!("Multiplication failed");
         }
     }
diff --git a/app-sdk/src/ecalls.rs b/app-sdk/src/ecalls.rs
index ae2dfd6..37fa6b5 100644
--- a/app-sdk/src/ecalls.rs
+++ b/app-sdk/src/ecalls.rs
@@ -55,8 +55,8 @@ pub(crate) trait EcallsInterface {
     /// - `len_m`: Length of `m`.
     ///
     /// # Returns
-    /// `true` on success, `false` on error.
-    fn bn_modm(r: *mut u8, n: *const u8, len: usize, m: *const u8, len_m: usize) -> bool;
+    /// 1 on success, 0 on error.
+    fn bn_modm(r: *mut u8, n: *const u8, len: usize, m: *const u8, len_m: usize) -> u32;
 
     /// Adds two big numbers `a` and `b` modulo `m`, storing the result in `r`.
     ///
@@ -69,7 +69,7 @@ pub(crate) trait EcallsInterface {
     ///
     /// # Returns
     /// `true` on success, `false` on error.
-    fn bn_addm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> bool;
+    fn bn_addm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> u32;
 
     /// Subtracts two big numbers `a` and `b` modulo `m`, storing the result in `r`.
     ///
@@ -82,7 +82,7 @@ pub(crate) trait EcallsInterface {
     ///
     /// # Returns
     /// `true` on success, `false` on error.
-    fn bn_subm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> bool;
+    fn bn_subm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> u32;
 
     /// Multiplies two big numbers `a` and `b` modulo `m`, storing the result in `r`.
     ///
@@ -95,7 +95,7 @@ pub(crate) trait EcallsInterface {
     ///
     /// # Returns
     /// `true` on success, `false` on error.
-    fn bn_multm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> bool;
+    fn bn_multm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> u32;
 
     /// Computes `a` to the power of `e` modulo `m`, storing the result in `r`.
     ///
@@ -116,7 +116,7 @@ pub(crate) trait EcallsInterface {
         len_e: usize,
         m: *const u8,
         len: usize,
-    ) -> bool;
+    ) -> u32;
 }
 
 pub(crate) use ecalls_module::*;
diff --git a/app-sdk/src/ecalls_native.rs b/app-sdk/src/ecalls_native.rs
index c6894be..eea908b 100644
--- a/app-sdk/src/ecalls_native.rs
+++ b/app-sdk/src/ecalls_native.rs
@@ -64,39 +64,39 @@ impl EcallsInterface for Ecall {
         return n_bytes_to_copy;
     }
 
-    fn bn_modm(r: *mut u8, n: *const u8, len: usize, m: *const u8, len_m: usize) -> bool {
+    fn bn_modm(r: *mut u8, n: *const u8, len: usize, m: *const u8, len_m: usize) -> u32 {
         if len > MAX_BIGNUMBER_SIZE || len_m > MAX_BIGNUMBER_SIZE {
-            return false;
+            return 0;
         }
 
         if len_m > len_m {
-            return false;
+            return 0;
         }
 
         let n = unsafe { Self::to_bigint(n, len) };
         let m = unsafe { Self::to_bigint(m, len_m) };
 
         if m.is_zero() {
-            return false;
+            return 0;
         }
 
         let result = n % &m;
         let result_bytes = result.to_bytes_be();
 
         if result_bytes.len() > len {
-            return false;
+            return 0;
         }
 
         unsafe {
             Self::copy_result(r, &result_bytes, len);
         }
 
-        true
+        1
     }
 
-    fn bn_addm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> bool {
+    fn bn_addm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> u32 {
         if len > MAX_BIGNUMBER_SIZE {
-            return false;
+            return 0;
         }
 
         let a = unsafe { Self::to_bigint(a, len) };
@@ -104,30 +104,30 @@ impl EcallsInterface for Ecall {
         let m = unsafe { Self::to_bigint(m, len) };
 
         if a >= m || b >= m {
-            return false;
+            return 0;
         }
 
         if m.is_zero() {
-            return false;
+            return 0;
         }
 
         let result = (a + b) % &m;
         let result_bytes = result.to_bytes_be();
 
         if result_bytes.len() > len {
-            return false;
+            return 0;
         }
 
         unsafe {
             Self::copy_result(r, &result_bytes, len);
         }
 
-        true
+        1
     }
 
-    fn bn_subm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> bool {
+    fn bn_subm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> u32 {
         if len > MAX_BIGNUMBER_SIZE {
-            return false;
+            return 0;
         }
 
         let a = unsafe { Self::to_bigint(a, len) };
@@ -135,11 +135,11 @@ impl EcallsInterface for Ecall {
         let m = unsafe { Self::to_bigint(m, len) };
 
         if a >= m || b >= m {
-            return false;
+            return 0;
         }
 
         if m.is_zero() {
-            return false;
+            return 0;
         }
 
         // the `+ &m` is to avoid negative numbers, since BigUints must be non-negative
@@ -147,19 +147,19 @@ impl EcallsInterface for Ecall {
         let result_bytes = result.to_bytes_be();
 
         if result_bytes.len() > len {
-            return false;
+            return 0;
         }
 
         unsafe {
             Self::copy_result(r, &result_bytes, len);
         }
 
-        true
+        1
     }
 
-    fn bn_multm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> bool {
+    fn bn_multm(r: *mut u8, a: *const u8, b: *const u8, m: *const u8, len: usize) -> u32 {
         if len > MAX_BIGNUMBER_SIZE {
-            return false;
+            return 0;
         }
 
         let a = unsafe { Self::to_bigint(a, len) };
@@ -167,25 +167,25 @@ impl EcallsInterface for Ecall {
         let m = unsafe { Self::to_bigint(m, len) };
 
         if a >= m || b >= m {
-            return false;
+            return 0;
         }
 
         if m.is_zero() {
-            return false;
+            return 0;
         }
 
         let result = (a * b) % &m;
         let result_bytes = result.to_bytes_be();
 
         if result_bytes.len() > len {
-            return false;
+            return 0;
         }
 
         unsafe {
             Self::copy_result(r, &result_bytes, len);
         }
 
-        true
+        1
     }
 
     fn bn_powm(
@@ -195,9 +195,9 @@ impl EcallsInterface for Ecall {
         len_e: usize,
         m: *const u8,
         len: usize,
-    ) -> bool {
+    ) -> u32 {
         if len > MAX_BIGNUMBER_SIZE || len_e > MAX_BIGNUMBER_SIZE {
-            return false;
+            return 0;
         }
 
         let a = unsafe { Self::to_bigint(a, len) };
@@ -205,25 +205,25 @@ impl EcallsInterface for Ecall {
         let m = unsafe { Self::to_bigint(m, len) };
 
         if a >= m {
-            return false;
+            return 0;
         }
 
         if m.is_zero() {
-            return false;
+            return 0;
         }
 
         let result = a.modpow(&e, &m);
         let result_bytes = result.to_bytes_be();
 
         if result_bytes.len() > len {
-            return false;
+            return 0;
         }
 
         unsafe {
             Self::copy_result(r, &result_bytes, len);
         }
 
-        true
+        1
     }
 }
 
diff --git a/app-sdk/src/ecalls_riscv.rs b/app-sdk/src/ecalls_riscv.rs
index e51b3fc..4502e86 100644
--- a/app-sdk/src/ecalls_riscv.rs
+++ b/app-sdk/src/ecalls_riscv.rs
@@ -169,7 +169,7 @@ macro_rules! ecall5 {
     };
 }
 
-macro_rules! ecall5 {
+macro_rules! ecall6 {
     // ECALL with 6 arguments and returning a value
     ($fn_name:ident, $syscall_number:expr,
      ($arg1:ident: $arg1_type:ty),
@@ -230,9 +230,9 @@ impl EcallsInterface for Ecall {
     ecall2v!(xsend, ECALL_XSEND, (buffer: *const u8), (size: usize));
     ecall2!(xrecv, ECALL_XRECV, (buffer: *mut u8), (size: usize), usize);
 
-    ecall5!(bn_modm, ECALL_MODM, (r: *mut u8), (n: *const u8), (len: usize), (m: *const u8), (len_m: usize), bool);
-    ecall5!(bn_addm, ECALL_ADDM, (r: *mut u8), (a: *const u8), (b: *const u8), (m: *const u8), (len: usize), bool);
-    ecall5!(bn_subm, ECALL_SUBM, (r: *mut u8), (a: *const u8), (b: *const u8), (m: *const u8), (len: usize), bool);
-    ecall5!(bn_multm, ECALL_MULTM, (r: *mut u8), (a: *const u8), (b: *const u8), (m: *const u8), (len: usize), bool);
-    ecall6!(bn_powm, ECALL_POWM, (r: *mut u8), (a: *const u8), (e: *const u8), (len_e: usize), (m: *const u8), (len: usize), bool);
+    ecall5!(bn_modm, ECALL_MODM, (r: *mut u8), (n: *const u8), (len: usize), (m: *const u8), (len_m: usize), u32);
+    ecall5!(bn_addm, ECALL_ADDM, (r: *mut u8), (a: *const u8), (b: *const u8), (m: *const u8), (len: usize), u32);
+    ecall5!(bn_subm, ECALL_SUBM, (r: *mut u8), (a: *const u8), (b: *const u8), (m: *const u8), (len: usize), u32);
+    ecall5!(bn_multm, ECALL_MULTM, (r: *mut u8), (a: *const u8), (b: *const u8), (m: *const u8), (len: usize), u32);
+    ecall6!(bn_powm, ECALL_POWM, (r: *mut u8), (a: *const u8), (e: *const u8), (len_e: usize), (m: *const u8), (len: usize), u32);
 }
diff --git a/apps/test/client/.cargo/config.toml b/apps/test/client/.cargo/config.toml
new file mode 100644
index 0000000..8af59dd
--- /dev/null
+++ b/apps/test/client/.cargo/config.toml
@@ -0,0 +1,2 @@
+[env]
+RUST_TEST_THREADS = "1"
diff --git a/apps/test/client/Cargo.toml b/apps/test/client/Cargo.toml
index cca9adc..52c769a 100644
--- a/apps/test/client/Cargo.toml
+++ b/apps/test/client/Cargo.toml
@@ -3,6 +3,9 @@ name = "vnd-test-client"
 version = "0.1.0"
 edition = "2021"
 
+[features]
+speculos-tests = []
+
 [dependencies]
 clap = { version = "4.5.17", features = ["derive"] }
 hex = "0.4.3"
@@ -11,6 +14,9 @@ ledger-transport-hid = "0.11.0"
 sdk = { package = "vanadium-client-sdk", path = "../../../client-sdk"}
 tokio = { version = "1.38.1", features = ["io-util", "macros", "net", "rt", "rt-multi-thread", "sync"] }
 
+[dev-dependencies]
+hex-literal = "0.4.1"
+
 [lib]
 name = "vnd_test_client"
 path = "src/lib.rs"
diff --git a/apps/test/client/tests/common/mod.rs b/apps/test/client/tests/common/mod.rs
new file mode 100644
index 0000000..fd556d2
--- /dev/null
+++ b/apps/test/client/tests/common/mod.rs
@@ -0,0 +1,61 @@
+use std::process::{Child, Command};
+use std::sync::Arc;
+use std::thread::sleep;
+use std::time::Duration;
+use vnd_test_client::TestClient;
+
+use sdk::{
+    transport::{Transport, TransportTcp, TransportWrapper},
+    vanadium_client::VanadiumAppClient,
+};
+
+pub struct TestSetup {
+    pub client: TestClient,
+    child: Child,
+}
+
+impl TestSetup {
+    async fn new() -> Self {
+        let vanadium_binary = std::env::var("VANADIUM_BINARY")
+            .unwrap_or_else(|_| "../../../vm/build/nanos2/bin/app.elf".to_string());
+        let vapp_binary = std::env::var("VAPP_BINARY").unwrap_or_else(|_| {
+            "../app/target/riscv32i-unknown-none-elf/release/vnd-test".to_string()
+        });
+
+        let child = Command::new("speculos")
+            .arg(vanadium_binary)
+            .arg("--display")
+            .arg("headless")
+            .spawn()
+            .expect("Failed to start speculos process");
+
+        sleep(Duration::from_secs(1));
+
+        let transport_raw: Arc<
+            dyn Transport<Error = Box<dyn std::error::Error + Send + Sync>> + Send + Sync,
+        > = Arc::new(
+            TransportTcp::new()
+                .await
+                .expect("Unable to get TCP transport. Is speculos running?"),
+        );
+        let transport = TransportWrapper::new(transport_raw.clone());
+
+        let (vanadium_client, _) = VanadiumAppClient::new(&vapp_binary, Arc::new(transport), None)
+            .await
+            .expect("Failed to create client");
+
+        let client = TestClient::new(Box::new(vanadium_client));
+
+        TestSetup { client, child }
+    }
+}
+
+impl Drop for TestSetup {
+    fn drop(&mut self) {
+        self.child.kill().expect("Failed to kill speculos process");
+    }
+}
+
+pub async fn setup() -> TestSetup {
+    TestSetup::new().await
+}
diff --git a/apps/test/client/tests/integration_test.rs b/apps/test/client/tests/integration_test.rs
new file mode 100644
index 0000000..49e3d51
--- /dev/null
+++ b/apps/test/client/tests/integration_test.rs
@@ -0,0 +1,88 @@
+#![cfg(feature = "speculos-tests")]
+
+mod common;
+
+use hex_literal::hex;
+
+#[tokio::test]
+async fn test_reverse() {
+    let mut setup = common::setup().await;
+
+    #[rustfmt::skip]
+    let testcases: Vec<(Vec<u8>, Vec<u8>)> = vec![
+        (hex!("1122334455").to_vec(), hex!("5544332211").to_vec()),
+    ];
+
+    for (input, expected) in testcases {
+        assert_eq!(setup.client.reverse(&input).await.unwrap(), expected);
+    }
+}
+
+#[tokio::test]
+async fn test_add_numbers() {
+    let mut setup = common::setup().await;
+
+    #[rustfmt::skip]
+    let testcases: Vec<(u32, u64)> = vec![
+        (0, 0),
+        (1, 1),
+        (100, 5050),
+    ];
+
+    for (input, expected) in testcases {
+        assert_eq!(setup.client.add_numbers(input).await.unwrap(), expected);
+    }
+}
+
+#[tokio::test]
+async fn test_b58enc() {
+    let mut setup = common::setup().await;
+
+    #[rustfmt::skip]
+    let testcases: Vec<(&str, &str)> = vec![
+        ("Hello World!", "2NEpo7TZRRrLZSi2U"),
+        ("The quick brown fox jumps over the lazy dog.", "USm3fpXnKG5EUBx2ndxBDMPVciP5hGey2Jh4NDv6gmeo1LkMeiKrLJUUBk6Z"),
+    ];
+
+    for (input, expected) in testcases {
+        assert_eq!(
+            setup.client.b58enc(&input.as_bytes()).await.unwrap(),
+            expected.as_bytes().to_vec()
+        );
+    }
+}
+
+#[tokio::test]
+async fn test_sha256() {
+    let mut setup = common::setup().await;
+
+    #[rustfmt::skip]
+    let testcases: Vec<(&str, Vec<u8>)> = vec![
+        ("", hex!("e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855").to_vec()),
+        ("abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq", hex!("248d6a61d20638b8e5c026930c3e6039a33ce45964ff2167f6ecedd419db06c1").to_vec()),
+    ];
+
+    for (input, expected) in testcases {
+        assert_eq!(
+            setup.client.sha256(&input.as_bytes()).await.unwrap(),
+            expected
+        );
+    }
+}
+
+#[tokio::test]
+async fn test_nprimes() {
+    let mut setup = common::setup().await;
+
+    #[rustfmt::skip]
+    let testcases: Vec<(u32, u32)> = vec![
+        (0, 0),
+        (5, 3),
+        (100, 25),
+        (1000, 168),
+    ];
+
+    for (input, expected) in testcases {
+        assert_eq!(setup.client.nprimes(input).await.unwrap(), expected);
+    }
+}
diff --git a/ledger_app.toml b/ledger_app.toml
new file mode 100644
index 0000000..3fbfa28
--- /dev/null
+++ b/ledger_app.toml
@@ -0,0 +1,4 @@
+[app]
+build_directory = "./vm/"
+sdk = "Rust"
+devices = ["nanos+", "stax", "flex"]
diff --git a/vm/ledger_app.toml b/vm/ledger_app.toml
deleted file mode 100644
index cb24deb..0000000
--- a/vm/ledger_app.toml
+++ /dev/null
@@ -1,7 +0,0 @@
-[app]
-build_directory = "./"
-sdk = "Rust"
-devices = ["nanox", "nanos+", "stax", "flex"]
-
-[tests]
-pytest_directory = "./tests/"