Set up a test harness for the flipperzero crate

The tests can be run with `cargo test` from within the `crates/`
directory.

crates/.cargo/config.toml

@@ -1,4 +1,5 @@
 [target.thumbv7em-none-eabihf]
+runner = "../tools/cargo-runner.sh"
 rustflags = [
     # CPU is Cortex-M4 (STM32WB55)
     "-C", "target-cpu=cortex-m4",

crates/flipperzero/Cargo.toml

@@ -18,7 +18,7 @@ all-features = true
 
 [lib]
 bench = false
-test = false
+harness = false
 
 [dependencies]
 flipperzero-sys.workspace = true

crates/flipperzero/src/lib.rs

@@ -1,6 +1,7 @@
 //! High-level bindings for the Flipper Zero.
 
 #![no_std]
+#![cfg_attr(test, no_main)]
 
 #[cfg(feature = "alloc")]
 extern crate alloc;
@@ -16,3 +17,56 @@ pub mod __internal {
     // Re-export for use in macros
     pub use ufmt;
 }
+
+// Infrastructure for running unit tests.
+#[cfg(test)]
+mod tests {
+    // Required for panic handler
+    extern crate flipperzero_rt;
+
+    // Required for allocator
+    #[cfg(feature = "alloc")]
+    extern crate flipperzero_alloc;
+
+    use core::time::Duration;
+
+    use flipperzero_rt::{entry, manifest};
+    use flipperzero_sys as sys;
+
+    use crate::{furi::thread, println};
+
+    manifest!(name = "Rust Unit Tests");
+    entry!(main);
+
+    // Test runner entry point
+    fn main(_args: *mut u8) -> i32 {
+        let heap_before = unsafe { sys::memmgr_get_free_heap() };
+        let cycle_counter = unsafe { sys::furi_get_tick() };
+
+        // TODO: Collect and run tests
+        let failed = 0;
+
+        println!("");
+        println!("Failed tests: {}\r", failed);
+
+        // Time report
+        println!(
+            "Consumed: {} ms\r",
+            unsafe { sys::furi_get_tick() } - cycle_counter
+        );
+
+        // Wait for tested services and apps to deallocate memory
+        thread::sleep(Duration::from_millis(200));
+        let heap_after = unsafe { sys::memmgr_get_free_heap() };
+        println!("Leaked: {}\r", heap_before - heap_after);
+
+        // Final Report
+        if failed == 0 {
+            println!("Status: PASSED\r");
+            0
+        } else {
+            println!("Status: FAILED\r");
+            1
+        }
+    }
+}

tools/cargo-runner.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+# Figure out where this script is located (which is also where the tools are).
+SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
+
+# Change directory to the tools directory, to ensure the CWD doesn't contain any
+# .cargo/config files that would prevent us from building on the host machine.
+cd $SCRIPT_DIR
+
+# Run the given FAP binary on a connected Flipper Zero.
+cargo run --quiet --release --bin run-fap -- $@