implemented more safeguards and autodiscovery

tests/safety_test.rs

@@ -0,0 +1,56 @@
+use anyhow::Result;
+use std::fs;
+use std::path::PathBuf;
+use ember_tune_rs::sal::safety::{HardwareStateGuard, TdpLimitMicroWatts};
+use crate::common::fakesys::FakeSysBuilder;
+
+mod common;
+
+#[test]
+fn test_hardware_state_guard_panic_restoration() {
+    let fake = FakeSysBuilder::new();
+    let pl1_path = fake.base_path().join("sys/class/powercap/intel-rapl:0/constraint_0_power_limit_uw");
+    
+    fake.add_rapl("intel-rapl:0", "1000", "15000000"); // 15W original
+
+    let target_files = vec![pl1_path.clone()];
+    
+    // Simulate a scope where the guard is active
+    {
+        let mut _guard = HardwareStateGuard::acquire(&target_files, &[]).expect("Failed to acquire guard");
+        
+        // Modify the file
+        fs::write(&pl1_path, "25000000").expect("Failed to write new value");
+        assert_eq!(fs::read_to_string(&pl1_path).unwrap().trim(), "25000000");
+        
+        // Guard is dropped here (simulating end of scope or panic)
+    }
+
+    // Verify restoration
+    let restored = fs::read_to_string(&pl1_path).expect("Failed to read restored file");
+    assert_eq!(restored.trim(), "15000000");
+}
+
+#[test]
+fn test_tdp_limit_bounds_checking() {
+    // 1. Valid value
+    assert!(TdpLimitMicroWatts::new(15_000_000).is_ok());
+    
+    // 2. Too low (Dangerous 0W or below 5W)
+    let low_res = TdpLimitMicroWatts::new(1_000_000);
+    assert!(low_res.is_err());
+    assert!(low_res.unwrap_err().to_string().contains("below safety floor"));
+
+    // 3. Too high (> 80W)
+    let high_res = TdpLimitMicroWatts::new(100_000_000);
+    assert!(high_res.is_err());
+    assert!(high_res.unwrap_err().to_string().contains("exceeds safety ceiling"));
+}
+
+#[test]
+fn test_0w_tdp_regression_prevention() {
+    // The prime directive is to never set 0W.
+    // Ensure the new() constructor explicitly fails for 0.
+    let zero_res = TdpLimitMicroWatts::new(0);
+    assert!(zero_res.is_err());
+}