diff --git a/src/backend.rs b/src/backend.rs
index d35f857..33dd9a5 100644
--- a/src/backend.rs
+++ b/src/backend.rs
@@ -443,98 +443,3 @@ pub(crate) fn transcribe_with_whisper_rs(
         "Transcription requires the 'whisper' feature. Rebuild with --features whisper (and optional gpu-cuda/gpu-hip)."
     ))
 }
-
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use std::env as std_env;
-    use std::sync::{Mutex, OnceLock};
-
-    // Serialize environment variable modifications across tests in this module
-    static ENV_LOCK: OnceLock<Mutex<()>> = OnceLock::new();
-
-    #[test]
-    fn test_select_backend_auto_prefers_cuda_then_hip_then_vulkan_then_cpu() {
-        let _guard = ENV_LOCK.get_or_init(|| Mutex::new(())).lock().unwrap();
-        // Clear overrides
-        unsafe {
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_CUDA");
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_HIP");
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_VULKAN");
-        }
-        // No GPU -> CPU
-        let sel = select_backend(BackendKind::Auto, &crate::Config::default()).unwrap();
-        assert_eq!(sel.chosen, BackendKind::Cpu);
-
-        // Vulkan only -> Vulkan
-        unsafe { std_env::set_var("POLYSCRIBE_TEST_FORCE_VULKAN", "1"); }
-        let sel = select_backend(BackendKind::Auto, &crate::Config::default()).unwrap();
-        assert_eq!(sel.chosen, BackendKind::Vulkan);
-
-        // HIP only -> HIP (and preferred over Vulkan)
-        unsafe {
-            std_env::set_var("POLYSCRIBE_TEST_FORCE_HIP", "1");
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_VULKAN");
-        }
-        let sel = select_backend(BackendKind::Auto, &crate::Config::default()).unwrap();
-        assert_eq!(sel.chosen, BackendKind::Hip);
-
-        // CUDA only -> CUDA (and preferred over HIP)
-        unsafe { std_env::set_var("POLYSCRIBE_TEST_FORCE_CUDA", "1"); }
-        let sel = select_backend(BackendKind::Auto, &crate::Config::default()).unwrap();
-        assert_eq!(sel.chosen, BackendKind::Cuda);
-
-        // Cleanup
-        unsafe {
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_CUDA");
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_HIP");
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_VULKAN");
-        }
-    }
-
-    #[test]
-    fn test_select_backend_explicit_unavailable_errors_with_guidance() {
-        let _guard = ENV_LOCK.get_or_init(|| Mutex::new(())).lock().unwrap();
-        // Ensure all off
-        unsafe {
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_CUDA");
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_HIP");
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_VULKAN");
-        }
-        // CUDA requested but unavailable -> error with guidance
-        let err = select_backend(BackendKind::Cuda, &crate::Config::default()).err().expect("expected error");
-        let msg = format!("{}", err);
-        assert!(msg.contains("Requested CUDA backend"), "unexpected msg: {msg}");
-        assert!(msg.contains("How to fix"), "expected guidance text in: {msg}");
-
-        // HIP requested but unavailable -> error with guidance
-        let err = select_backend(BackendKind::Hip, &crate::Config::default()).err().expect("expected error");
-        let msg = format!("{}", err);
-        assert!(msg.contains("ROCm/HIP"), "unexpected msg: {msg}");
-        assert!(msg.contains("How to fix"), "expected guidance text in: {msg}");
-
-        // Vulkan requested but unavailable -> error with guidance
-        let err = select_backend(BackendKind::Vulkan, &crate::Config::default()).err().expect("expected error");
-        let msg = format!("{}", err);
-        assert!(msg.contains("Vulkan"), "unexpected msg: {msg}");
-        assert!(msg.contains("How to fix"), "expected guidance text in: {msg}");
-
-        // Now verify success when explicitly available via overrides
-        unsafe { std_env::set_var("POLYSCRIBE_TEST_FORCE_CUDA", "1"); }
-        assert!(select_backend(BackendKind::Cuda, &crate::Config::default()).is_ok());
-        unsafe {
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_CUDA");
-            std_env::set_var("POLYSCRIBE_TEST_FORCE_HIP", "1");
-        }
-        assert!(select_backend(BackendKind::Hip, &crate::Config::default()).is_ok());
-        unsafe {
-            std_env::remove_var("POLYSCRIBE_TEST_FORCE_HIP");
-            std_env::set_var("POLYSCRIBE_TEST_FORCE_VULKAN", "1");
-        }
-        assert!(select_backend(BackendKind::Vulkan, &crate::Config::default()).is_ok());
-
-        // Cleanup
-        unsafe { std_env::remove_var("POLYSCRIBE_TEST_FORCE_VULKAN"); }
-    }
-}