diff --git a/.cargo/config.toml b/.cargo/config.toml
index c424c85..b7f1846 100644
--- a/.cargo/config.toml
+++ b/.cargo/config.toml
@@ -8,3 +8,4 @@ rustflags = [
   "-C", "target-cpu=cortex-a53",
   "-C", "embed-bitcode=yes",
 ]
+runner = "cargo make test-runner"
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index e5b3c54..85c4962 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -46,7 +46,18 @@ jobs:
       run: rustup component add rust-src llvm-tools-preview
 
     - name: "Install build tools"
-      run: cargo install cargo-make
+      run: cargo install cargo-make cargo-binutils
+
+    - name: "Validate rust-lld"
+      run: |
+        which rust-lld || echo "Not found"
+        otool -L ~/.cargo/bin/rust-lld
+      if: runner.os == 'macOS'
+
+    - name: "Print Tools Version"
+      run: |
+        cargo make --version
+        cargo objcopy --version
 
     - name: "Deny Warnings"
       run: cargo make build
@@ -55,6 +66,8 @@ jobs:
 
     - name: Install QEMU (Linux)
       run: |
+        sudo apt install software-properties-common
+        sudo add-apt-repository ppa:jacob/virtualisation
         sudo apt update
         sudo apt install qemu-system-aarch64
       if: runner.os == 'Linux'
@@ -85,7 +98,8 @@ jobs:
     - name: 'Build kernel'
       run: cargo make build
 
-    # TODO: add tests runner
+    - name: 'Run tests'
+      run: cargo make test
 
   check_formatting:
     name: "Check Formatting"
diff --git a/Justfile b/Justfile
index b955a30..c21df01 100644
--- a/Justfile
+++ b/Justfile
@@ -14,3 +14,6 @@ clean:
 
 clippy:
     cargo make clippy
+
+test:
+    cargo make test
diff --git a/Makefile.toml b/Makefile.toml
index 644a6b7..0cef496 100644
--- a/Makefile.toml
+++ b/Makefile.toml
@@ -29,7 +29,8 @@ QEMU_CONTAINER_CMD = "qemu-system-aarch64"
 #
 # -d in_asm,unimp,int
 QEMU_OPTS = "-M raspi3 -d int -semihosting"
-QEMU_SERIAL = "-serial null -serial stdio"
+QEMU_SERIAL_OPTS = "-serial null -serial stdio"
+QEMU_TESTS_OPTS = "-nographic"
 QEMU = "qemu-system-aarch64"
 
 # For gdb connection:
diff --git a/README.md b/README.md
index 9c9d5fb..77da3c7 100644
--- a/README.md
+++ b/README.md
@@ -47,6 +47,12 @@ To build kernel for Raspberry Pi and copy it to SDCard mounted at `/Volumes/BOOT
 just device
 ```
 
+To run tests (tests require QEMU):
+
+```
+just test
+```
+
 On the device boot SD card you'll need a configuration file instructing RasPi to launch in 64-bit mode.
 
 ```
diff --git a/nucleus/Makefile.toml b/nucleus/Makefile.toml
index e56f538..40787e1 100644
--- a/nucleus/Makefile.toml
+++ b/nucleus/Makefile.toml
@@ -9,10 +9,26 @@ script = [
     "${OBJCOPY} ${OBJCOPY_PARAMS} ${CARGO_MAKE_WORKSPACE_WORKING_DIRECTORY}/target/${DEFAULT_TARGET}/release/vesper ${KERNEL_BIN}"
 ]
 
+[tasks.custom-binary]
+script = [
+    "cp ${@} ${CARGO_MAKE_WORKSPACE_WORKING_DIRECTORY}/target/`basename ${@}`.elf",
+    "${OBJCOPY} ${OBJCOPY_PARAMS} ${@} ${CARGO_MAKE_WORKSPACE_WORKING_DIRECTORY}/target/`basename ${@}`.bin"
+]
+
 [tasks.build]
 env = { "TARGET_FEATURES" = "" }
 args = ["build", "${BUILD_STD}", "--target=${TARGET_JSON}", "--release", "--features=${TARGET_FEATURES}"]
 
+[tasks.test]
+env = { "TARGET_FEATURES" = "${QEMU_FEATURES}" }
+args = ["test", "${BUILD_STD}", "--target=${TARGET_JSON}", "--features=${TARGET_FEATURES}"]
+
+[tasks.test-runner]
+dependencies = ["custom-binary"]
+script = [
+    "${QEMU} ${QEMU_OPTS} ${QEMU_TESTS_OPTS} -dtb ${CARGO_MAKE_WORKSPACE_WORKING_DIRECTORY}/targets/bcm2710-rpi-3-b-plus.dtb -kernel ${CARGO_MAKE_WORKSPACE_WORKING_DIRECTORY}/target/`basename ${@}`.bin"
+]
+
 [tasks.build-qemu]
 env = { "TARGET_FEATURES" = "${QEMU_FEATURES}" }
 command = "cargo"
diff --git a/nucleus/src/macros.rs b/nucleus/src/macros.rs
new file mode 100644
index 0000000..c986bb9
--- /dev/null
+++ b/nucleus/src/macros.rs
@@ -0,0 +1,32 @@
+/*
+ * SPDX-License-Identifier: BlueOak-1.0.0
+ */
+
+// https://doc.rust-lang.org/src/std/macros.rs.html
+#[macro_export]
+macro_rules! print {
+    ($($arg:tt)*) => ($crate::macros::_print(format_args!($($arg)*)));
+}
+
+// https://doc.rust-lang.org/src/std/macros.rs.html
+#[macro_export]
+macro_rules! println {
+    () => (print!("\n"));
+    ($($arg:tt)*) => ({
+        $crate::macros::_print(format_args_nl!($($arg)*));
+    })
+}
+
+#[doc(hidden)]
+#[cfg(not(any(test, qemu)))]
+pub fn _print(_args: core::fmt::Arguments) {
+    // @todo real system implementation
+}
+
+#[doc(hidden)]
+#[cfg(any(test, qemu))] // qemu feature not enabled here?? we pass --features=qemu to cargo test
+pub fn _print(args: core::fmt::Arguments) {
+    use crate::{qemu, write_to};
+    let mut buf = [0u8; 512];
+    qemu::semihosting_sys_write0_call(write_to::c_show(&mut buf, args).unwrap());
+}
diff --git a/nucleus/src/main.rs b/nucleus/src/main.rs
index 4a6fea2..466d97d 100644
--- a/nucleus/src/main.rs
+++ b/nucleus/src/main.rs
@@ -3,13 +3,26 @@
  */
 #![no_std]
 #![no_main]
+#![feature(asm)]
+#![feature(format_args_nl)]
+#![feature(custom_test_frameworks)]
+#![test_runner(crate::tests::test_runner)]
+#![reexport_test_harness_main = "test_main"]
 
 #[cfg(not(target_arch = "aarch64"))]
 use architecture_not_supported_sorry;
 
+extern crate rlibc; // To enable linking memory intrinsics.
+
 #[macro_use]
 pub mod arch;
 pub use arch::*;
+mod macros;
+#[cfg(feature = "qemu")]
+mod qemu;
+#[cfg(test)]
+mod tests;
+mod write_to;
 
 entry!(kmain);
 
@@ -17,6 +30,9 @@ entry!(kmain);
 // arch crate is responsible for calling this
 #[inline]
 pub fn kmain() -> ! {
+    #[cfg(test)]
+    test_main();
+
     endless_sleep()
 }
 
diff --git a/nucleus/src/qemu.rs b/nucleus/src/qemu.rs
new file mode 100644
index 0000000..0612d81
--- /dev/null
+++ b/nucleus/src/qemu.rs
@@ -0,0 +1,11 @@
+#[cfg(test)]
+pub fn semihosting_sys_write0_call(text: &str) {
+    // SAFETY: text must be \0-terminated!
+    unsafe {
+        asm!(
+            "mov w0, #0x04
+             hlt #0xF000"
+             , in("x1") text.as_ptr() as u64
+        );
+    }
+}
diff --git a/nucleus/src/tests.rs b/nucleus/src/tests.rs
new file mode 100644
index 0000000..cae6ed9
--- /dev/null
+++ b/nucleus/src/tests.rs
@@ -0,0 +1,14 @@
+//============================================================================
+// Testing environment
+//============================================================================
+use crate::println;
+
+#[cfg(test)]
+pub fn test_runner(tests: &[&dyn Fn()]) {
+    println!("Running {} tests", tests.len());
+    for test in tests {
+        test();
+    }
+    println!("[success]");
+    qemu_exit::aarch64::exit_success();
+}