test(gui-client): fix missed mutations (#3753)

I added unit tests for these pure or mostly-pure functions that
`cargo-mutants` said were not covered.

It also picked up a lot of I/O-performing functions that I ignored for
now. (They're hard to test)

rust/gui-client/src-tauri/src/client/about.rs

@@ -10,3 +10,17 @@ pub(crate) fn get_cargo_version() -> String {
 pub(crate) fn get_git_version() -> String {
     GIT_VERSION.to_string()
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn version() {
+        let cargo = super::get_cargo_version();
+        let git = super::get_git_version();
+
+        assert!(cargo != "Unknown", "{}", cargo);
+        assert!(git != "Unknown", "{}", git);
+        assert!(cargo.len() >= 2, "{}", cargo);
+        assert!(git.len() >= 6, "{}", git);
+    }
+}

rust/gui-client/src-tauri/src/client/auth.rs

@@ -267,6 +267,14 @@ mod tests {
         SecretString::new(x.into())
     }
 
+    #[test]
+    fn actor_name_path() {
+        assert!(super::actor_name_path()
+            .expect("`actor_name_path` should return Ok")
+            .components()
+            .any(|x| x == std::path::Component::Normal("dev.firezone.client".as_ref())));
+    }
+
     /// Runs everything in one test so that `cargo test` can't multi-thread it
     /// This should work around a bug we had <https://github.com/firezone/firezone/issues/3256>
     #[test]

rust/gui-client/src-tauri/src/client/deep_link/windows.rs

@@ -162,3 +162,14 @@ fn set_registry_values(id: &str, exe: &str) -> Result<(), io::Error> {
 fn named_pipe_path(id: &str) -> String {
     format!(r"\\.\pipe\{}", id)
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn named_pipe_path() {
+        assert_eq!(
+            super::named_pipe_path("dev.firezone.client"),
+            r"\\.\pipe\dev.firezone.client"
+        );
+    }
+}

rust/gui-client/src-tauri/src/client/known_dirs.rs

@@ -118,3 +118,18 @@ mod imp {
         )
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn smoke() {
+        for dir in [device_id(), logs(), runtime(), session(), settings()] {
+            let dir = dir.expect("should have gotten Some(path)");
+            assert!(dir
+                .components()
+                .any(|x| x == std::path::Component::Normal("dev.firezone.client".as_ref())));
+        }
+    }
+}