Make cargo test work

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index b3eadc1..55492aa 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,5 +15,5 @@
 
 script:
   - cargo fmt --all -- --check
-  - cargo test --lib --all
+  - cargo test --workspace
   - ./build_examples.sh

src/lib.rs

diff --git a/src/lib.rs b/src/lib.rs
index 6d49e29..ae46436 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,9 +6,7 @@
     naked_functions,
     ptr_offset_from
 )]
-#![no_std]
-
-extern crate alloc;
+#![cfg_attr(any(target_arch = "arm", target_arch = "riscv32"), no_std)]
 
 mod callback;
 
@@ -31,7 +29,6 @@
 pub mod temperature;
 pub mod timer;
 pub mod unwind_symbols;
-pub use libtock_codegen::main;
 
 #[cfg(any(target_arch = "arm", target_arch = "riscv32"))]
 pub mod entry_point;
@@ -41,6 +38,8 @@
 
 pub mod syscalls;
 
+pub use libtock_codegen::main;
+
 // Dummy structure to force importing the panic_handler and other no_std elements when nothing else
 // is imported.
 pub struct LibTock;

src/result.rs

diff --git a/src/result.rs b/src/result.rs
index a7f40e1..9b26c31 100644
--- a/src/result.rs
+++ b/src/result.rs
@@ -11,6 +11,13 @@
     Other(OtherError),
 }
 
+#[cfg(not(any(target_arch = "arm", target_arch = "riscv32")))]
+impl core::fmt::Debug for TockError {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        writeln!(f, "impl Debug only for test builds")
+    }
+}
+
 #[derive(Copy, Clone)]
 pub struct SubscribeError {
     pub driver_number: usize,

src/temperature.rs

diff --git a/src/temperature.rs b/src/temperature.rs
index e50cbe2..28e366f 100644
--- a/src/temperature.rs
+++ b/src/temperature.rs
@@ -51,8 +51,6 @@
 #[cfg(test)]
 mod test {
     use super::*;
-    use alloc::string::String;
-    use alloc::string::ToString;
 
     #[test]
     fn render_temperature() {