diff --git a/src/manager.rs b/src/manager.rs
index 0a6f1e5..435be1c 100644
--- a/src/manager.rs
+++ b/src/manager.rs
@@ -277,7 +277,7 @@ impl SteamOSManager {
             .map_err(anyhow_to_zbus)
     }
 
-    #[zbus(property, name = "ManualGPUClock")]
+    #[zbus(property(emits_changed_signal = "false"), name = "ManualGPUClock")]
     async fn manual_gpu_clock(&self) -> zbus::fdo::Result<u32> {
         get_gpu_clocks().await.map_err(anyhow_to_zbus_fdo)
     }
@@ -467,7 +467,7 @@ mod test {
     #[tokio::test]
     async fn gpu_performance_level() {
         let test = start("GPUPerformanceLevel").await;
-        power::setup_test().await;
+        power::test::setup().await;
 
         let proxy = GPUPerformanceLevelProxy::new(&test.connection)
             .await
@@ -490,6 +490,37 @@ mod test {
         );
     }
 
+    #[zbus::proxy(
+        interface = "com.steampowered.SteamOSManager1.Manager",
+        default_service = "com.steampowered.SteamOSManager1.Test.ManualGPUClock",
+        default_path = "/com/steampowered/SteamOSManager1"
+    )]
+    trait ManualGPUClock {
+        #[zbus(property, name = "ManualGPUClock")]
+        fn manual_gpu_clock(&self) -> zbus::Result<u32>;
+
+        #[zbus(property, name = "ManualGPUClock")]
+        fn set_manual_gpu_clock(&self, clocks: u32) -> zbus::Result<()>;
+    }
+
+    #[tokio::test]
+    async fn manual_gpu_clock() {
+        let test = start("ManualGPUClock").await;
+
+        let proxy = ManualGPUClockProxy::new(&test.connection).await.unwrap();
+
+        assert!(proxy.manual_gpu_clock().await.is_err());
+
+        power::test::write_clocks(1600).await;
+        assert_eq!(proxy.manual_gpu_clock().await.unwrap(), 1600);
+
+        proxy.set_manual_gpu_clock(200).await.expect("proxy_set");
+        power::test::expect_clocks(200);
+
+        assert!(proxy.set_manual_gpu_clock(100).await.is_err());
+        power::test::expect_clocks(200);
+    }
+
     #[zbus::proxy(
         interface = "com.steampowered.SteamOSManager1.Manager",
         default_service = "com.steampowered.SteamOSManager1.Test.Version",
diff --git a/src/power.rs b/src/power.rs
index c145749..f31ec65 100644
--- a/src/power.rs
+++ b/src/power.rs
@@ -201,26 +201,51 @@ pub async fn set_tdp_limit(limit: u32) -> Result<()> {
 }
 
 #[cfg(test)]
-pub async fn setup_test() {
-    let filename = path(GPU_PERFORMANCE_LEVEL_PATH);
-    fs::create_dir_all(filename.parent().unwrap())
-        .await
-        .expect("create_dir_all");
-}
-
-#[cfg(test)]
-mod test {
+pub mod test {
     use super::*;
     use crate::testing;
     use anyhow::anyhow;
     use tokio::fs::{create_dir_all, read_to_string, remove_dir, write};
 
+    pub async fn setup() {
+        let filename = path(GPU_PERFORMANCE_LEVEL_PATH);
+        create_dir_all(filename.parent().unwrap())
+            .await
+            .expect("create_dir_all");
+    }
+
+    pub async fn write_clocks(mhz: u32) {
+        let filename = path(GPU_CLOCKS_PATH);
+        create_dir_all(filename.parent().unwrap())
+            .await
+            .expect("create_dir_all");
+
+        let contents = format!(
+            "OD_SCLK:
+0:       {mhz}Mhz
+1:       {mhz}Mhz
+OD_RANGE:
+SCLK:     200Mhz       1600Mhz
+CCLK:    1400Mhz       3500Mhz
+CCLK_RANGE in Core0:
+0:       1400Mhz
+1:       3500Mhz\n"
+        );
+
+        write(filename.as_path(), contents).await.expect("write");
+    }
+
+    pub async fn expect_clocks(mhz: u32) {
+        let clocks = read_to_string(path(GPU_CLOCKS_PATH)).await.expect("read");
+        assert_eq!(clocks, format!("s 0 {mhz}\ns 1 {mhz}\nc\n"));
+    }
+
     #[tokio::test]
     async fn test_get_gpu_performance_level() {
         let h = testing::start();
 
         let filename = path(GPU_PERFORMANCE_LEVEL_PATH);
-        setup_test().await;
+        setup().await;
         assert!(get_gpu_performance_level().await.is_err());
 
         write(filename.as_path(), "auto\n").await.expect("write");
@@ -264,7 +289,7 @@ mod test {
         let h = testing::start();
 
         let filename = path(GPU_PERFORMANCE_LEVEL_PATH);
-        setup_test().await;
+        setup().await;
 
         set_gpu_performance_level(GPUPerformanceLevel::Auto)
             .await
@@ -314,7 +339,9 @@ mod test {
 
         assert!(get_tdp_limit().await.is_err());
 
-        write(hwmon.join("hwmon5").join(TDP_LIMIT1), "15000000").await.expect("write");
+        write(hwmon.join("hwmon5").join(TDP_LIMIT1), "15000000")
+            .await
+            .expect("write");
         assert_eq!(get_tdp_limit().await.unwrap(), 15);
     }
 
@@ -381,21 +408,11 @@ mod test {
     #[tokio::test]
     async fn test_get_gpu_clocks() {
         let h = testing::start();
-
-        const contents: &str = "OD_SCLK:
-0:       1600Mhz
-1:       1600Mhz
-OD_RANGE:
-SCLK:     200Mhz       1600Mhz
-CCLK:    1400Mhz       3500Mhz
-CCLK_RANGE in Core0:
-0:       1400Mhz
-1:       3500Mhz\n";
         let filename = path(GPU_PERFORMANCE_LEVEL_PATH);
-        setup_test().await;
+        setup().await;
 
         assert!(get_gpu_clocks().await.is_err());
-        write(path(GPU_CLOCKS_PATH), contents).await.expect("write");
+        write_clocks(1600).await;
 
         assert_eq!(get_gpu_clocks().await.unwrap(), 1600);
     }
@@ -404,23 +421,16 @@ CCLK_RANGE in Core0:
     async fn test_set_gpu_clocks() {
         let h = testing::start();
 
-        let filename = path(GPU_CLOCKS_PATH);
         assert!(set_gpu_clocks(1600).await.is_err());
-        setup_test().await;
+        setup().await;
 
         assert!(set_gpu_clocks(100).await.is_err());
         assert!(set_gpu_clocks(2000).await.is_err());
 
         assert!(set_gpu_clocks(200).await.is_ok());
-        assert_eq!(
-            read_to_string(filename.as_path()).await.expect("string"),
-            "s 0 200\ns 1 200\nc\n"
-        );
+        expect_clocks(200).await;
 
         assert!(set_gpu_clocks(1600).await.is_ok());
-        assert_eq!(
-            read_to_string(filename.as_path()).await.expect("string"),
-            "s 0 1600\ns 1 1600\nc\n"
-        );
+        expect_clocks(1600).await;
     }
 }