diff --git a/wfassoc/tests/common.rs b/wfassoc/tests/common.rs
new file mode 100644
index 0000000..c66a0a8
--- /dev/null
+++ b/wfassoc/tests/common.rs
@@ -0,0 +1,16 @@
+/// Check whether we are in sandbox.
+///
+/// # Panics
+///
+/// Panic if we are not in sandbox (we can not perform dangerous test).
+/// Return if we are in sandbox environment.
+pub fn check_sandbox() {
+    assert!(
+        std::env::var("SANDBOXIE").is_ok(),
+        concat!(
+            "Non-sandbox environment detected. ",
+            "Executing these test in non-sandbox environment is VERY dangerous. ",
+            "Please set \"SANDBOXIE\" environment variable to explicitly indicate you are running these test in sandbox environment."
+        )
+    )
+}
diff --git a/wfassoc/tests/highlevel.rs b/wfassoc/tests/highlevel.rs
new file mode 100644
index 0000000..28251e1
--- /dev/null
+++ b/wfassoc/tests/highlevel.rs
@@ -0,0 +1,7 @@
+use wfassoc::highlevel::*;
+mod common;
+
+#[test]
+fn test() {
+    common::check_sandbox();
+}
diff --git a/wfassoc/tests/lowlevel.rs b/wfassoc/tests/lowlevel.rs
new file mode 100644
index 0000000..51ce5b7
--- /dev/null
+++ b/wfassoc/tests/lowlevel.rs
@@ -0,0 +1,330 @@
+use std::ops::Deref;
+use std::str::FromStr;
+use std::sync::LazyLock;
+use wfassoc::lowlevel::*;
+use wfassoc::win32::concept;
+mod common;
+
+static EXT: LazyLock<concept::Ext> = LazyLock::new(|| concept::Ext::from_str(".pacfg").unwrap());
+static APP_FILE: LazyLock<concept::FileName> =
+    LazyLock::new(|| concept::FileName::from_str("passoc.exe").unwrap());
+static PROG_ID: LazyLock<LosseProgId> = LazyLock::new(|| "Passoc.Pacfg".into());
+static ICON: LazyLock<IconResVariant> =
+    LazyLock::new(|| r"%SystemRoot%\System32\imageres.dll,-72".into());
+static VERB: LazyLock<ShellVerb> = LazyLock::new(|| {
+    let verb = concept::Verb::from_str("open").unwrap();
+    let cmdline = concept::CmdLine::from_str("notepad.exe %1").unwrap();
+    ShellVerb::new(verb, cmdline)
+});
+
+// region: ExtKey
+
+#[test]
+fn test_ext_key() {
+    common::check_sandbox();
+
+    fn tester(scope: Scope, view: View) {
+        let mut key = ExtKey::new(EXT.clone());
+
+        // delete and ensure
+        let rv = key.delete(scope);
+        assert!(rv.is_ok());
+        let rv = key.is_exist(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+        let rv = key.ensure(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), true);
+        let rv = key.is_exist(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), true);
+        let rv = key.ensure(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+
+        // get/set default
+        let rv = key.set_default(scope, Some(&PROG_ID));
+        assert!(rv.is_ok());
+        let rv = key.get_default(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), Some(PROG_ID.clone()));
+        let rv = key.set_default(scope, None);
+        assert!(rv.is_ok());
+        let rv = key.get_default(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), None);
+
+        // test open with progids
+        let rv = key.is_in_open_with_progids(view, &PROG_ID);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+
+        let rv = key.add_into_open_with_progids(scope, &PROG_ID);
+        assert!(rv.is_ok());
+        let rv = key.is_in_open_with_progids(view, &PROG_ID);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), true);
+
+        let rv = key.get_open_with_progids(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), Some(vec![PROG_ID.clone()]));
+
+        let rv = key.remove_from_open_with_progids(scope, &PROG_ID);
+        assert!(rv.is_ok());
+        let rv = key.is_in_open_with_progids(view, &PROG_ID);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+
+        // clean up
+        let rv = key.delete(scope);
+        assert!(rv.is_ok());
+    }
+
+    tester(Scope::User, View::User);
+    tester(Scope::System, View::System);
+}
+
+// endregion
+
+// region: ProgIdKey
+
+#[test]
+fn test_prog_id_key() {
+    common::check_sandbox();
+
+    static LEGACY_NAME: LazyLock<StrResVariant> = LazyLock::new(|| "Passoc Pacfg File".into());
+    static FRIENDLY_TYPE_NAME: LazyLock<StrResVariant> =
+        LazyLock::new(|| "Passoc Pacfg File Type".into());
+
+    fn tester(scope: Scope, view: View) {
+        let mut key = ProgIdKey::new(PROG_ID.clone());
+
+        // delete and ensure
+        let rv = key.delete(scope);
+        assert!(rv.is_ok());
+        let rv = key.is_exist(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+        let rv = key.ensure(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), true);
+        let rv = key.is_exist(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), true);
+        let rv = key.ensure(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+
+        // get/set default (friendly name, legacy)
+        let rv = key.set_default(scope, Some(&LEGACY_NAME));
+        assert!(rv.is_ok());
+        let rv = key.get_default(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), Some(LEGACY_NAME.clone()));
+        let rv = key.set_default(scope, None);
+        assert!(rv.is_ok());
+        let rv = key.get_default(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), None);
+
+        // get/set friendly type name
+        let rv = key.set_friendly_type_name(scope, Some(&FRIENDLY_TYPE_NAME));
+        assert!(rv.is_ok());
+        let rv = key.get_friendly_type_name(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), Some(FRIENDLY_TYPE_NAME.clone()));
+        let rv = key.set_friendly_type_name(scope, None);
+        assert!(rv.is_ok());
+        let rv = key.get_friendly_type_name(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), None);
+
+        // get/set shell verb
+        let rv = key.set_shell_verb(scope, Some(&VERB));
+        assert!(rv.is_ok());
+        let rv = key.get_shell_verb(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), Some(VERB.clone()));
+        let rv = key.set_shell_verb(scope, None);
+        assert!(rv.is_ok());
+        let rv = key.get_shell_verb(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), None);
+
+        // get/set default icon
+        let rv = key.set_default_icon(scope, Some(&ICON));
+        assert!(rv.is_ok());
+        let rv = key.get_default_icon(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), Some(ICON.clone()));
+        let rv = key.set_default_icon(scope, None);
+        assert!(rv.is_ok());
+        let rv = key.get_default_icon(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), None);
+
+        // clean up
+        let rv = key.delete(scope);
+        assert!(rv.is_ok());
+    }
+
+    tester(Scope::User, View::User);
+    tester(Scope::System, View::System);
+}
+
+// endregion
+
+// region: AppPathsKey
+
+#[test]
+fn test_app_paths_key() {
+    common::check_sandbox();
+
+    static APP_PATH: &str = r"C:\Program Files\Passoc\passoc.exe";
+    static APP_DIR: &str = r"C:\Program Files\Passoc";
+
+    fn tester(scope: Scope) {
+        let mut key = AppPathsKey::new(APP_FILE.clone());
+
+        // delete and ensure
+        let rv = key.delete(scope);
+        assert!(rv.is_ok());
+        let rv = key.is_exist(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+        let rv = key.ensure(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), true);
+        let rv = key.is_exist(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), true);
+        let rv = key.ensure(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+
+        // get/set default
+        let rv = key.set_default(scope, APP_PATH);
+        assert!(rv.is_ok());
+        let rv = key.get_default(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), APP_PATH);
+
+        // get/set path
+        let rv = key.set_path(scope, APP_DIR);
+        assert!(rv.is_ok());
+        let rv = key.get_path(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), APP_DIR);
+
+        // clean up
+        let rv = key.delete(scope);
+        assert!(rv.is_ok());
+    }
+
+    tester(Scope::User);
+    tester(Scope::System);
+}
+
+// endregion
+
+// region: ApplicationsKey
+
+#[test]
+fn test_applications_key() {
+    common::check_sandbox();
+
+    static FRIENDLY_APP_NAME: LazyLock<StrResVariant> =
+        LazyLock::new(|| "Passoc Application".into());
+
+    fn tester(scope: Scope, view: View) {
+        let mut key = ApplicationsKey::new(APP_FILE.clone());
+
+        // delete and ensure
+        let rv = key.delete(scope);
+        assert!(rv.is_ok());
+        let rv = key.is_exist(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+        let rv = key.ensure(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), true);
+        let rv = key.is_exist(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), true);
+        let rv = key.ensure(scope);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+
+        // get/set shell verb
+        let rv = key.set_shell_verb(scope, Some(&VERB));
+        assert!(rv.is_ok());
+        let rv = key.get_shell_verb(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), Some(VERB.clone()));
+        let rv = key.set_shell_verb(scope, None);
+        assert!(rv.is_ok());
+        let rv = key.get_shell_verb(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), None);
+
+        // get/set default icon
+        let rv = key.set_default_icon(scope, Some(&ICON));
+        assert!(rv.is_ok());
+        let rv = key.get_default_icon(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), Some(ICON.clone()));
+        let rv = key.set_default_icon(scope, None);
+        assert!(rv.is_ok());
+        let rv = key.get_default_icon(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), None);
+
+        // get/set friendly app name
+        let rv = key.set_friendly_app_name(scope, Some(&FRIENDLY_APP_NAME));
+        assert!(rv.is_ok());
+        let rv = key.get_friendly_app_name(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), Some(FRIENDLY_APP_NAME.clone()));
+        let rv = key.set_friendly_app_name(scope, None);
+        assert!(rv.is_ok());
+        let rv = key.get_friendly_app_name(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), None);
+
+        // get/set supported types
+        let rv = key.set_supported_types(scope, Some(&vec![EXT.deref()]));
+        assert!(rv.is_ok());
+        let rv = key.get_supported_types(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), Some(vec![EXT.clone()]));
+        let rv = key.set_supported_types(scope, None);
+        assert!(rv.is_ok());
+        let rv = key.get_supported_types(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), None);
+
+        // get/set no open with
+        let rv = key.get_no_open_with(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+        let rv = key.set_no_open_with(scope, true);
+        assert!(rv.is_ok());
+        let rv = key.get_no_open_with(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), true);
+        let rv = key.set_no_open_with(scope, false);
+        assert!(rv.is_ok());
+        let rv = key.get_no_open_with(view);
+        assert!(rv.is_ok());
+        assert_eq!(rv.unwrap(), false);
+
+        // clean up
+        let rv = key.delete(scope);
+        assert!(rv.is_ok());
+    }
+
+    tester(Scope::User, View::User);
+    tester(Scope::System, View::System);
+}
+
+// endregion