diff --git a/backon/Cargo.toml b/backon/Cargo.toml
index 2d169e3..c486847 100644
--- a/backon/Cargo.toml
+++ b/backon/Cargo.toml
@@ -36,6 +36,7 @@ gloo-timers = { version = "0.3", optional = true }
 [dev-dependencies]
 anyhow = "1"
 reqwest = "0.12"
+spin = "0.9.8"
 
 [target.'cfg(target_arch = "wasm32")'.dev-dependencies]
 tokio = { version = "1", features = [
diff --git a/backon/src/blocking_retry.rs b/backon/src/blocking_retry.rs
index 56a80f4..227ad9b 100644
--- a/backon/src/blocking_retry.rs
+++ b/backon/src/blocking_retry.rs
@@ -198,8 +198,11 @@ where
 
 #[cfg(test)]
 mod tests {
+    use alloc::string::ToString;
+    use alloc::vec;
+    use alloc::vec::Vec;
     use core::time::Duration;
-    use std::sync::Mutex;
+    use spin::Mutex;
 
     use super::*;
     use crate::ExponentialBuilder;
@@ -224,7 +227,7 @@ mod tests {
         let error_times = Mutex::new(0);
 
         let f = || {
-            let mut x = error_times.lock().unwrap();
+            let mut x = error_times.lock();
             *x += 1;
             Err::<(), anyhow::Error>(anyhow::anyhow!("not retryable"))
         };
@@ -240,7 +243,7 @@ mod tests {
         assert_eq!("not retryable", result.unwrap_err().to_string());
         // `f` always returns error "not retryable", so it should be executed
         // only once.
-        assert_eq!(*error_times.lock().unwrap(), 1);
+        assert_eq!(*error_times.lock(), 1);
         Ok(())
     }
 
@@ -249,8 +252,8 @@ mod tests {
         let error_times = Mutex::new(0);
 
         let f = || {
-            println!("I have been called!");
-            let mut x = error_times.lock().unwrap();
+            // println!("I have been called!");
+            let mut x = error_times.lock();
             *x += 1;
             Err::<(), anyhow::Error>(anyhow::anyhow!("retryable"))
         };
@@ -266,7 +269,7 @@ mod tests {
         assert_eq!("retryable", result.unwrap_err().to_string());
         // `f` always returns error "retryable", so it should be executed
         // 4 times (retry 3 times).
-        assert_eq!(*error_times.lock().unwrap(), 4);
+        assert_eq!(*error_times.lock(), 4);
         Ok(())
     }
 
diff --git a/backon/src/blocking_retry_with_context.rs b/backon/src/blocking_retry_with_context.rs
index f61f78f..383fd34 100644
--- a/backon/src/blocking_retry_with_context.rs
+++ b/backon/src/blocking_retry_with_context.rs
@@ -117,7 +117,7 @@ where
 
     /// Call the retried function.
     ///
-    /// TODO: implement [`std::ops::FnOnce`] after it stable.
+    /// TODO: implement [`FnOnce`] after it stable.
     pub fn call(mut self) -> (Ctx, Result<T, E>) {
         let mut ctx = self.ctx.take().expect("context must be valid");
         loop {
@@ -147,14 +147,13 @@ where
 
 #[cfg(test)]
 mod tests {
-    use core::time::Duration;
-
-    use anyhow::anyhow;
-    use std::sync::Mutex;
-
     use super::*;
     use crate::ExponentialBuilder;
+    use alloc::string::ToString;
+    use anyhow::anyhow;
     use anyhow::Result;
+    use core::time::Duration;
+    use std::sync::Mutex;
 
     struct Test;
 
diff --git a/backon/src/lib.rs b/backon/src/lib.rs
index 705eb24..79bd9be 100644
--- a/backon/src/lib.rs
+++ b/backon/src/lib.rs
@@ -96,6 +96,7 @@
 #![deny(unused_qualifications)]
 #![no_std]
 #[cfg(feature = "std")]
+extern crate alloc;
 extern crate std;
 
 mod backoff;
diff --git a/backon/src/retry.rs b/backon/src/retry.rs
index 617a527..da3e7d7 100644
--- a/backon/src/retry.rs
+++ b/backon/src/retry.rs
@@ -320,7 +320,10 @@ where
 #[cfg(test)]
 #[cfg(any(feature = "tokio-sleep", feature = "gloo-timers-sleep"))]
 mod tests {
-    use std::{future::ready, time::Duration};
+    use alloc::string::ToString;
+    use alloc::vec;
+    use alloc::vec::Vec;
+    use core::{future::ready, time::Duration};
     use tokio::sync::Mutex;
 
     #[cfg(target_arch = "wasm32")]
diff --git a/backon/src/retry_with_context.rs b/backon/src/retry_with_context.rs
index 7de7bec..53f7ba2 100644
--- a/backon/src/retry_with_context.rs
+++ b/backon/src/retry_with_context.rs
@@ -362,9 +362,9 @@ where
 
 #[cfg(test)]
 mod tests {
-    use core::time::Duration;
-
+    use alloc::string::ToString;
     use anyhow::{anyhow, Result};
+    use core::time::Duration;
     use tokio::sync::Mutex;
 
     #[cfg(target_arch = "wasm32")]