From c142db6e23f197274b011b049292aae0313082dc Mon Sep 17 00:00:00 2001
From: "Christopher J. McClellan" <chris.mcclellan203@gmail.com>
Date: Sun, 30 Dec 2018 19:17:58 -0500
Subject: [PATCH 1/3] Add example of writing tests that run on host machine

---
 examples/test_on_host.rs | 44 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 examples/test_on_host.rs

diff --git a/examples/test_on_host.rs b/examples/test_on_host.rs
new file mode 100644
index 0000000..bb39de1
--- /dev/null
+++ b/examples/test_on_host.rs
@@ -0,0 +1,44 @@
+//! Conditionally compiling tests with std and our executable with no_std.
+//!
+//! Ensure there are no targets specified under `[build]` in `.cargo/config`
+//! In order to make this work, we lose the convenience of having a default target that isn't the
+//! host.
+//!
+//! cargo build --example test_on_host --target thumbv7m-none-eabi
+//! cargo test --example test_on_host
+
+#![cfg_attr(test, allow(unused_imports))]
+
+#![cfg_attr(not(test), no_std)]
+#![cfg_attr(not(test), no_main)]
+
+// pick a panicking behavior
+#[cfg(not(test))]
+extern crate panic_halt; // you can put a breakpoint on `rust_begin_unwind` to catch panics
+// extern crate panic_abort; // requires nightly
+// extern crate panic_itm; // logs messages over ITM; requires ITM support
+// extern crate panic_semihosting; // logs messages to the host stderr; requires a debugger
+
+use cortex_m::asm;
+use cortex_m_rt::entry;
+
+#[cfg(not(test))]
+#[entry]
+fn main() -> ! {
+    asm::nop(); // To not have main optimize to abort in release mode, remove when you add code
+
+    loop {
+        // your code goes here
+    }
+}
+
+#[cfg(test)]
+mod test {
+  use super::*;
+
+  #[test]
+  fn foo() {
+    println!("tests work!");
+    assert!(1 == 1);
+  }
+}

From 0e2aadf8f279f03a012c909ab1e0e1151838127f Mon Sep 17 00:00:00 2001
From: "Christopher J. McClellan" <chris.mcclellan203@gmail.com>
Date: Sun, 30 Dec 2018 19:55:24 -0500
Subject: [PATCH 2/3] Make sure we can actually test prod code

---
 examples/test_on_host.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/examples/test_on_host.rs b/examples/test_on_host.rs
index bb39de1..b5f386b 100644
--- a/examples/test_on_host.rs
+++ b/examples/test_on_host.rs
@@ -32,6 +32,10 @@ fn main() -> ! {
     }
 }
 
+fn add(a: i32, b: i32) -> i32 {
+    a + b
+}
+
 #[cfg(test)]
 mod test {
   use super::*;
@@ -39,6 +43,6 @@ mod test {
   #[test]
   fn foo() {
     println!("tests work!");
-    assert!(1 == 1);
+    assert!(2 == add(1,1));
   }
 }

From e58549b2ec06111b0037ce6e282c085dd7c4c84d Mon Sep 17 00:00:00 2001
From: "Christopher J. McClellan" <chris.mcclellan203@gmail.com>
Date: Mon, 31 Dec 2018 07:01:16 -0500
Subject: [PATCH 3/3] Add more documentation for testing on host

---
 examples/test_on_host.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/examples/test_on_host.rs b/examples/test_on_host.rs
index b5f386b..1c75ed1 100644
--- a/examples/test_on_host.rs
+++ b/examples/test_on_host.rs
@@ -1,5 +1,14 @@
 //! Conditionally compiling tests with std and our executable with no_std.
 //!
+//! Rust's built in unit testing framework requires the standard library,
+//! but we need to build our final executable with no_std.
+//! The testing framework also generates a `main` method, so we need to only use the `#[entry]`
+//! annotation when building our final image.
+//! For more information on why this example works, see this excellent blog post.
+//! https://os.phil-opp.com/unit-testing/
+//!
+//! Running this example:
+//!
 //! Ensure there are no targets specified under `[build]` in `.cargo/config`
 //! In order to make this work, we lose the convenience of having a default target that isn't the
 //! host.