9 files changed, 1574 insertions, 0 deletions
diff --git a/testing/geckodriver/marionette/Cargo.toml b/testing/geckodriver/marionette/Cargo.toml
new file mode 100644
index 0000000000..6e4c4acc88
--- /dev/null
+++ b/testing/geckodriver/marionette/Cargo.toml
@@ -0,0 +1,14 @@
+[package]
+name = "marionette"
+version = "0.2.0"
+authors = ["Mozilla"]
+description = "Library implementing the client side of Gecko's Marionette remote automation protocol."
+edition = "2018"
+keywords = ["mozilla", "firefox", "marionette", "webdriver"]
+license = "MPL-2.0"
+repository = "https://hg.mozilla.org/mozilla-central/file/tip/testing/geckodriver/marionette"
+
+[dependencies]
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+serde_repr = "0.1"
diff --git a/testing/geckodriver/marionette/src/common.rs b/testing/geckodriver/marionette/src/common.rs
new file mode 100644
index 0000000000..e819757e73
--- /dev/null
+++ b/testing/geckodriver/marionette/src/common.rs
@@ -0,0 +1,240 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use serde::ser::SerializeMap;
+use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
+use serde_json::Value;
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct BoolValue {
+    value: bool,
+}
+
+impl BoolValue {
+    pub fn new(val: bool) -> Self {
+        BoolValue { value: val }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct Cookie {
+    pub name: String,
+    pub value: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub path: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub domain: Option<String>,
+    #[serde(default)]
+    pub secure: bool,
+    #[serde(default, rename = "httpOnly")]
+    pub http_only: bool,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub expiry: Option<Date>,
+    #[serde(skip_serializing_if = "Option::is_none", rename = "sameSite")]
+    pub same_site: Option<String>,
+}
+
+pub fn to_cookie<T, S>(data: T, serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+    T: Serialize,
+{
+    #[derive(Serialize)]
+    struct Wrapper<T> {
+        cookie: T,
+    }
+
+    Wrapper { cookie: data }.serialize(serializer)
+}
+
+pub fn from_cookie<'de, D, T>(deserializer: D) -> Result<T, D::Error>
+where
+    D: Deserializer<'de>,
+    T: serde::de::DeserializeOwned,
+    T: std::fmt::Debug,
+{
+    #[derive(Debug, Deserialize)]
+    struct Wrapper<T> {
+        cookie: T,
+    }
+
+    let w = Wrapper::deserialize(deserializer)?;
+    Ok(w.cookie)
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct Date(pub u64);
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum Frame {
+    Index(u16),
+    Element(String),
+    Parent,
+}
+
+impl Serialize for Frame {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut map = serializer.serialize_map(Some(1))?;
+        match self {
+            Frame::Index(nth) => map.serialize_entry("id", nth)?,
+            Frame::Element(el) => map.serialize_entry("element", el)?,
+            Frame::Parent => map.serialize_entry("id", &Value::Null)?,
+        }
+        map.end()
+    }
+}
+
+impl<'de> Deserialize<'de> for Frame {
+    fn deserialize<D>(deserializer: D) -> Result<Frame, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        #[derive(Debug, Deserialize)]
+        #[serde(rename_all = "lowercase")]
+        struct JsonFrame {
+            id: Option<u16>,
+            element: Option<String>,
+        }
+
+        let json = JsonFrame::deserialize(deserializer)?;
+        match (json.id, json.element) {
+            (Some(_id), Some(_element)) => Err(de::Error::custom("conflicting frame identifiers")),
+            (Some(id), None) => Ok(Frame::Index(id)),
+            (None, Some(element)) => Ok(Frame::Element(element)),
+            (None, None) => Ok(Frame::Parent),
+        }
+    }
+}
+
+// TODO(nupur): Bug 1567165 - Make WebElement in Marionette a unit struct
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct WebElement {
+    #[serde(rename = "element-6066-11e4-a52e-4f735466cecf")]
+    pub element: String,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct Timeouts {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub implicit: Option<u64>,
+    #[serde(default, rename = "pageLoad", skip_serializing_if = "Option::is_none")]
+    pub page_load: Option<u64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[allow(clippy::option_option)]
+    pub script: Option<Option<u64>>,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct Window {
+    pub handle: String,
+}
+
+pub fn to_name<T, S>(data: T, serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+    T: Serialize,
+{
+    #[derive(Serialize)]
+    struct Wrapper<T> {
+        name: T,
+    }
+
+    Wrapper { name: data }.serialize(serializer)
+}
+
+pub fn from_name<'de, D, T>(deserializer: D) -> Result<T, D::Error>
+where
+    D: Deserializer<'de>,
+    T: serde::de::DeserializeOwned,
+    T: std::fmt::Debug,
+{
+    #[derive(Debug, Deserialize)]
+    struct Wrapper<T> {
+        name: T,
+    }
+
+    let w = Wrapper::deserialize(deserializer)?;
+    Ok(w.name)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::test::{assert_de, assert_ser, assert_ser_de, ELEMENT_KEY};
+    use serde_json::json;
+
+    #[test]
+    fn test_cookie_default_values() {
+        let data = Cookie {
+            name: "hello".into(),
+            value: "world".into(),
+            path: None,
+            domain: None,
+            secure: false,
+            http_only: false,
+            expiry: None,
+            same_site: None,
+        };
+        assert_de(&data, json!({"name":"hello", "value":"world"}));
+    }
+
+    #[test]
+    fn test_json_frame_index() {
+        assert_ser_de(&Frame::Index(1234), json!({"id": 1234}));
+    }
+
+    #[test]
+    fn test_json_frame_element() {
+        assert_ser_de(&Frame::Element("elem".into()), json!({"element": "elem"}));
+    }
+
+    #[test]
+    fn test_json_frame_parent() {
+        assert_ser_de(&Frame::Parent, json!({ "id": null }));
+    }
+
+    #[test]
+    fn test_web_element() {
+        let data = WebElement {
+            element: "foo".into(),
+        };
+        assert_ser_de(&data, json!({ELEMENT_KEY: "foo"}));
+    }
+
+    #[test]
+    fn test_timeouts_with_all_params() {
+        let data = Timeouts {
+            implicit: Some(1000),
+            page_load: Some(200000),
+            script: Some(Some(60000)),
+        };
+        assert_ser_de(
+            &data,
+            json!({"implicit":1000,"pageLoad":200000,"script":60000}),
+        );
+    }
+
+    #[test]
+    fn test_timeouts_with_missing_params() {
+        let data = Timeouts {
+            implicit: Some(1000),
+            page_load: None,
+            script: None,
+        };
+        assert_ser_de(&data, json!({"implicit":1000}));
+    }
+
+    #[test]
+    fn test_timeouts_setting_script_none() {
+        let data = Timeouts {
+            implicit: Some(1000),
+            page_load: None,
+            script: Some(None),
+        };
+        assert_ser(&data, json!({"implicit":1000, "script":null}));
+    }
+}
diff --git a/testing/geckodriver/marionette/src/error.rs b/testing/geckodriver/marionette/src/error.rs
new file mode 100644
index 0000000000..6b05410047
--- /dev/null
+++ b/testing/geckodriver/marionette/src/error.rs
@@ -0,0 +1,184 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::error;
+use std::fmt;
+
+use serde::{Deserialize, Serialize};
+
+#[derive(Clone, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize, Deserialize)]
+#[serde(untagged)]
+pub(crate) enum Error {
+    Marionette(MarionetteError),
+}
+
+impl Error {
+    pub fn kind(&self) -> ErrorKind {
+        match *self {
+            Error::Marionette(ref err) => err.kind,
+        }
+    }
+}
+
+impl fmt::Debug for Error {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Error::Marionette(ref err) => fmt
+                .debug_struct("Marionette")
+                .field("kind", &err.kind)
+                .field("message", &err.message)
+                .field("stacktrace", &err.stack.clone())
+                .finish(),
+        }
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Error::Marionette(ref err) => write!(fmt, "{}: {}", err.kind, err.message),
+        }
+    }
+}
+
+impl error::Error for Error {
+    fn description(&self) -> &str {
+        match self {
+            Error::Marionette(_) => self.kind().as_str(),
+        }
+    }
+}
+
+#[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize, Deserialize)]
+pub struct MarionetteError {
+    #[serde(rename = "error")]
+    pub kind: ErrorKind,
+    #[serde(default = "empty_string")]
+    pub message: String,
+    #[serde(rename = "stacktrace", default = "empty_string")]
+    pub stack: String,
+}
+
+fn empty_string() -> String {
+    "".to_owned()
+}
+
+impl From<MarionetteError> for Error {
+    fn from(error: MarionetteError) -> Error {
+        Error::Marionette(error)
+    }
+}
+
+#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize, Deserialize)]
+pub enum ErrorKind {
+    #[serde(rename = "element click intercepted")]
+    ElementClickIntercepted,
+    #[serde(rename = "element not accessible")]
+    ElementNotAccessible,
+    #[serde(rename = "element not interactable")]
+    ElementNotInteractable,
+    #[serde(rename = "insecure certificate")]
+    InsecureCertificate,
+    #[serde(rename = "invalid argument")]
+    InvalidArgument,
+    #[serde(rename = "invalid cookie")]
+    InvalidCookieDomain,
+    #[serde(rename = "invalid element state")]
+    InvalidElementState,
+    #[serde(rename = "invalid selector")]
+    InvalidSelector,
+    #[serde(rename = "invalid session id")]
+    InvalidSessionId,
+    #[serde(rename = "javascript error")]
+    JavaScript,
+    #[serde(rename = "move target out of bounds")]
+    MoveTargetOutOfBounds,
+    #[serde(rename = "no such alert")]
+    NoSuchAlert,
+    #[serde(rename = "no such element")]
+    NoSuchElement,
+    #[serde(rename = "no such frame")]
+    NoSuchFrame,
+    #[serde(rename = "no such window")]
+    NoSuchWindow,
+    #[serde(rename = "script timeout")]
+    ScriptTimeout,
+    #[serde(rename = "session not created")]
+    SessionNotCreated,
+    #[serde(rename = "stale element reference")]
+    StaleElementReference,
+    #[serde(rename = "timeout")]
+    Timeout,
+    #[serde(rename = "unable to set cookie")]
+    UnableToSetCookie,
+    #[serde(rename = "unexpected alert open")]
+    UnexpectedAlertOpen,
+    #[serde(rename = "unknown command")]
+    UnknownCommand,
+    #[serde(rename = "unknown error")]
+    Unknown,
+    #[serde(rename = "unsupported operation")]
+    UnsupportedOperation,
+    #[serde(rename = "webdriver error")]
+    WebDriver,
+}
+
+impl ErrorKind {
+    pub(crate) fn as_str(self) -> &'static str {
+        use ErrorKind::*;
+        match self {
+            ElementClickIntercepted => "element click intercepted",
+            ElementNotAccessible => "element not accessible",
+            ElementNotInteractable => "element not interactable",
+            InsecureCertificate => "insecure certificate",
+            InvalidArgument => "invalid argument",
+            InvalidCookieDomain => "invalid cookie",
+            InvalidElementState => "invalid element state",
+            InvalidSelector => "invalid selector",
+            InvalidSessionId => "invalid session id",
+            JavaScript => "javascript error",
+            MoveTargetOutOfBounds => "move target out of bounds",
+            NoSuchAlert => "no such alert",
+            NoSuchElement => "no such element",
+            NoSuchFrame => "no such frame",
+            NoSuchWindow => "no such window",
+            ScriptTimeout => "script timeout",
+            SessionNotCreated => "session not created",
+            StaleElementReference => "stale eelement referencee",
+            Timeout => "timeout",
+            UnableToSetCookie => "unable to set cookie",
+            UnexpectedAlertOpen => "unexpected alert open",
+            UnknownCommand => "unknown command",
+            Unknown => "unknown error",
+            UnsupportedOperation => "unsupported operation",
+            WebDriver => "webdriver error",
+        }
+    }
+}
+
+impl fmt::Display for ErrorKind {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(fmt, "{}", self.as_str())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::test::assert_ser_de;
+    use serde_json::json;
+
+    #[test]
+    fn test_json_error() {
+        let err = MarionetteError {
+            kind: ErrorKind::Timeout,
+            message: "".into(),
+            stack: "".into(),
+        };
+        assert_ser_de(
+            &err,
+            json!({"error": "timeout", "message": "", "stacktrace": ""}),
+        );
+    }
+}
diff --git a/testing/geckodriver/marionette/src/lib.rs b/testing/geckodriver/marionette/src/lib.rs
new file mode 100644
index 0000000000..80817c5f5b
--- /dev/null
+++ b/testing/geckodriver/marionette/src/lib.rs
@@ -0,0 +1,14 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+pub mod error;
+
+pub mod common;
+pub mod marionette;
+pub mod message;
+pub mod result;
+pub mod webdriver;
+
+#[cfg(test)]
+mod test;
diff --git a/testing/geckodriver/marionette/src/marionette.rs b/testing/geckodriver/marionette/src/marionette.rs
new file mode 100644
index 0000000000..c06e2d60c7
--- /dev/null
+++ b/testing/geckodriver/marionette/src/marionette.rs
@@ -0,0 +1,69 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use serde::{Deserialize, Serialize};
+
+use crate::common::BoolValue;
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[allow(non_camel_case_types)]
+pub enum AppStatus {
+    eAttemptQuit,
+    eConsiderQuit,
+    eForceQuit,
+    eRestart,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub enum Command {
+    #[serde(rename = "Marionette:AcceptConnections")]
+    AcceptConnections(BoolValue),
+    #[serde(rename = "Marionette:Quit")]
+    DeleteSession { flags: Vec<AppStatus> },
+    #[serde(rename = "Marionette:GetContext")]
+    GetContext,
+    #[serde(rename = "Marionette:GetScreenOrientation")]
+    GetScreenOrientation,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::test::assert_ser_de;
+    use serde_json::json;
+
+    #[test]
+    fn test_json_command_accept_connections() {
+        assert_ser_de(
+            &Command::AcceptConnections(BoolValue::new(false)),
+            json!({"Marionette:AcceptConnections": {"value": false }}),
+        );
+    }
+
+    #[test]
+    fn test_json_command_delete_session() {
+        let data = &Command::DeleteSession {
+            flags: vec![AppStatus::eForceQuit],
+        };
+        assert_ser_de(data, json!({"Marionette:Quit": {"flags": ["eForceQuit"]}}));
+    }
+
+    #[test]
+    fn test_json_command_get_context() {
+        assert_ser_de(&Command::GetContext, json!("Marionette:GetContext"));
+    }
+
+    #[test]
+    fn test_json_command_get_screen_orientation() {
+        assert_ser_de(
+            &Command::GetScreenOrientation,
+            json!("Marionette:GetScreenOrientation"),
+        );
+    }
+
+    #[test]
+    fn test_json_command_invalid() {
+        assert!(serde_json::from_value::<Command>(json!("foo")).is_err());
+    }
+}
diff --git a/testing/geckodriver/marionette/src/message.rs b/testing/geckodriver/marionette/src/message.rs
new file mode 100644
index 0000000000..704d52f67b
--- /dev/null
+++ b/testing/geckodriver/marionette/src/message.rs
@@ -0,0 +1,336 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use serde::de::{self, SeqAccess, Unexpected, Visitor};
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use serde_json::{Map, Value};
+use serde_repr::{Deserialize_repr, Serialize_repr};
+use std::fmt;
+
+use crate::error::MarionetteError;
+use crate::marionette;
+use crate::result::MarionetteResult;
+use crate::webdriver;
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum Command {
+    WebDriver(webdriver::Command),
+    Marionette(marionette::Command),
+}
+
+impl Command {
+    pub fn name(&self) -> String {
+        let (command_name, _) = self.first_entry();
+        command_name
+    }
+
+    fn params(&self) -> Value {
+        let (_, params) = self.first_entry();
+        params
+    }
+
+    fn first_entry(&self) -> (String, serde_json::Value) {
+        match serde_json::to_value(self).unwrap() {
+            Value::String(cmd) => (cmd, Value::Object(Map::new())),
+            Value::Object(items) => {
+                let mut iter = items.iter();
+                let (cmd, params) = iter.next().unwrap();
+                (cmd.to_string(), params.clone())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize_repr, Deserialize_repr)]
+#[repr(u8)]
+enum MessageDirection {
+    Incoming = 0,
+    Outgoing = 1,
+}
+
+pub type MessageId = u32;
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct Request(pub MessageId, pub Command);
+
+impl Request {
+    pub fn id(&self) -> MessageId {
+        self.0
+    }
+
+    pub fn command(&self) -> &Command {
+        &self.1
+    }
+
+    pub fn params(&self) -> Value {
+        self.command().params()
+    }
+}
+
+impl Serialize for Request {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        (
+            MessageDirection::Incoming,
+            self.id(),
+            self.command().name(),
+            self.params(),
+        )
+            .serialize(serializer)
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub enum Response {
+    Result {
+        id: MessageId,
+        result: MarionetteResult,
+    },
+    Error {
+        id: MessageId,
+        error: MarionetteError,
+    },
+}
+
+impl Serialize for Response {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        match self {
+            Response::Result { id, result } => {
+                (MessageDirection::Outgoing, id, Value::Null, &result).serialize(serializer)
+            }
+            Response::Error { id, error } => {
+                (MessageDirection::Outgoing, id, &error, Value::Null).serialize(serializer)
+            }
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Serialize)]
+#[serde(untagged)]
+pub enum Message {
+    Incoming(Request),
+    Outgoing(Response),
+}
+
+struct MessageVisitor;
+
+impl<'de> Visitor<'de> for MessageVisitor {
+    type Value = Message;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("four-element array")
+    }
+
+    fn visit_seq<A: SeqAccess<'de>>(self, mut seq: A) -> Result<Self::Value, A::Error> {
+        let direction = seq
+            .next_element::<MessageDirection>()?
+            .ok_or_else(|| de::Error::invalid_length(0, &self))?;
+        let id: MessageId = seq
+            .next_element()?
+            .ok_or_else(|| de::Error::invalid_length(1, &self))?;
+
+        let msg = match direction {
+            MessageDirection::Incoming => {
+                let name: String = seq
+                    .next_element()?
+                    .ok_or_else(|| de::Error::invalid_length(2, &self))?;
+                let params: Value = seq
+                    .next_element()?
+                    .ok_or_else(|| de::Error::invalid_length(3, &self))?;
+
+                let command = match params {
+                    Value::Object(ref items) if !items.is_empty() => {
+                        let command_to_params = {
+                            let mut m = Map::new();
+                            m.insert(name, params);
+                            Value::Object(m)
+                        };
+                        serde_json::from_value(command_to_params).map_err(de::Error::custom)
+                    }
+                    Value::Object(_) | Value::Null => {
+                        serde_json::from_value(Value::String(name)).map_err(de::Error::custom)
+                    }
+                    x => Err(de::Error::custom(format!("unknown params type: {}", x))),
+                }?;
+                Message::Incoming(Request(id, command))
+            }
+
+            MessageDirection::Outgoing => {
+                let maybe_error: Option<MarionetteError> = seq
+                    .next_element()?
+                    .ok_or_else(|| de::Error::invalid_length(2, &self))?;
+
+                let response = if let Some(error) = maybe_error {
+                    seq.next_element::<Value>()?
+                        .ok_or_else(|| de::Error::invalid_length(3, &self))?
+                        .as_null()
+                        .ok_or_else(|| de::Error::invalid_type(Unexpected::Unit, &self))?;
+                    Response::Error { id, error }
+                } else {
+                    let result: MarionetteResult = seq
+                        .next_element()?
+                        .ok_or_else(|| de::Error::invalid_length(3, &self))?;
+                    Response::Result { id, result }
+                };
+
+                Message::Outgoing(response)
+            }
+        };
+
+        Ok(msg)
+    }
+}
+
+impl<'de> Deserialize<'de> for Message {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        deserializer.deserialize_seq(MessageVisitor)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use serde_json::json;
+
+    use super::*;
+
+    use crate::common::*;
+    use crate::error::{ErrorKind, MarionetteError};
+    use crate::test::assert_ser_de;
+
+    #[test]
+    fn test_incoming() {
+        let json =
+            json!([0, 42, "WebDriver:FindElement", {"using": "css selector", "value": "value"}]);
+        let find_element = webdriver::Command::FindElement(webdriver::Locator {
+            using: webdriver::Selector::Css,
+            value: "value".into(),
+        });
+        let req = Request(42, Command::WebDriver(find_element));
+        let msg = Message::Incoming(req);
+        assert_ser_de(&msg, json);
+    }
+
+    #[test]
+    fn test_incoming_empty_params() {
+        let json = json!([0, 42, "WebDriver:GetTimeouts", {}]);
+        let req = Request(42, Command::WebDriver(webdriver::Command::GetTimeouts));
+        let msg = Message::Incoming(req);
+        assert_ser_de(&msg, json);
+    }
+
+    #[test]
+    fn test_incoming_common_params() {
+        let json = json!([0, 42, "Marionette:AcceptConnections", {"value": false}]);
+        let params = BoolValue::new(false);
+        let req = Request(
+            42,
+            Command::Marionette(marionette::Command::AcceptConnections(params)),
+        );
+        let msg = Message::Incoming(req);
+        assert_ser_de(&msg, json);
+    }
+
+    #[test]
+    fn test_incoming_params_derived() {
+        assert!(serde_json::from_value::<Message>(
+            json!([0,42,"WebDriver:FindElement",{"using":"foo","value":"foo"}])
+        )
+        .is_err());
+        assert!(serde_json::from_value::<Message>(
+            json!([0,42,"Marionette:AcceptConnections",{"value":"foo"}])
+        )
+        .is_err());
+    }
+
+    #[test]
+    fn test_incoming_no_params() {
+        assert!(serde_json::from_value::<Message>(
+            json!([0,42,"WebDriver:GetTimeouts",{"value":true}])
+        )
+        .is_err());
+        assert!(serde_json::from_value::<Message>(
+            json!([0,42,"Marionette:Context",{"value":"foo"}])
+        )
+        .is_err());
+        assert!(serde_json::from_value::<Message>(
+            json!([0,42,"Marionette:GetScreenOrientation",{"value":true}])
+        )
+        .is_err());
+    }
+
+    #[test]
+    fn test_outgoing_result() {
+        let json = json!([1, 42, null, { "value": null }]);
+        let result = MarionetteResult::Null;
+        let msg = Message::Outgoing(Response::Result { id: 42, result });
+
+        assert_ser_de(&msg, json);
+    }
+
+    #[test]
+    fn test_outgoing_error() {
+        let json =
+            json!([1, 42, {"error": "no such element", "message": "", "stacktrace": ""}, null]);
+        let error = MarionetteError {
+            kind: ErrorKind::NoSuchElement,
+            message: "".into(),
+            stack: "".into(),
+        };
+        let msg = Message::Outgoing(Response::Error { id: 42, error });
+
+        assert_ser_de(&msg, json);
+    }
+
+    #[test]
+    fn test_invalid_type() {
+        assert!(
+            serde_json::from_value::<Message>(json!([2, 42, "WebDriver:GetTimeouts", {}])).is_err()
+        );
+        assert!(serde_json::from_value::<Message>(json!([3, 42, "no such element", {}])).is_err());
+    }
+
+    #[test]
+    fn test_missing_fields() {
+        // all fields are required
+        assert!(
+            serde_json::from_value::<Message>(json!([2, 42, "WebDriver:GetTimeouts"])).is_err()
+        );
+        assert!(serde_json::from_value::<Message>(json!([2, 42])).is_err());
+        assert!(serde_json::from_value::<Message>(json!([2])).is_err());
+        assert!(serde_json::from_value::<Message>(json!([])).is_err());
+    }
+
+    #[test]
+    fn test_unknown_command() {
+        assert!(serde_json::from_value::<Message>(json!([0, 42, "hooba", {}])).is_err());
+    }
+
+    #[test]
+    fn test_unknown_error() {
+        assert!(serde_json::from_value::<Message>(json!([1, 42, "flooba", {}])).is_err());
+    }
+
+    #[test]
+    fn test_message_id_bounds() {
+        let overflow = i64::from(std::u32::MAX) + 1;
+        let underflow = -1;
+
+        fn get_timeouts(message_id: i64) -> Value {
+            json!([0, message_id, "WebDriver:GetTimeouts", {}])
+        }
+
+        assert!(serde_json::from_value::<Message>(get_timeouts(overflow)).is_err());
+        assert!(serde_json::from_value::<Message>(get_timeouts(underflow)).is_err());
+    }
+}
diff --git a/testing/geckodriver/marionette/src/result.rs b/testing/geckodriver/marionette/src/result.rs
new file mode 100644
index 0000000000..95817c15f0
--- /dev/null
+++ b/testing/geckodriver/marionette/src/result.rs
@@ -0,0 +1,223 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use serde::de;
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use serde_json::Value;
+
+use crate::common::{Cookie, Timeouts, WebElement};
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct NewWindow {
+    handle: String,
+    #[serde(rename = "type")]
+    type_hint: String,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct WindowRect {
+    pub x: i32,
+    pub y: i32,
+    pub width: i32,
+    pub height: i32,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct ElementRect {
+    pub x: f64,
+    pub y: f64,
+    pub width: f64,
+    pub height: f64,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum MarionetteResult {
+    #[serde(deserialize_with = "from_value", serialize_with = "to_value")]
+    Bool(bool),
+    #[serde(deserialize_with = "from_value", serialize_with = "to_empty_value")]
+    Null,
+    NewWindow(NewWindow),
+    WindowRect(WindowRect),
+    ElementRect(ElementRect),
+    #[serde(deserialize_with = "from_value", serialize_with = "to_value")]
+    String(String),
+    Strings(Vec<String>),
+    #[serde(deserialize_with = "from_value", serialize_with = "to_value")]
+    WebElement(WebElement),
+    WebElements(Vec<WebElement>),
+    Cookies(Vec<Cookie>),
+    Timeouts(Timeouts),
+}
+
+fn to_value<T, S>(data: T, serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+    T: Serialize,
+{
+    #[derive(Serialize)]
+    struct Wrapper<T> {
+        value: T,
+    }
+
+    Wrapper { value: data }.serialize(serializer)
+}
+
+fn to_empty_value<S>(serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+{
+    #[derive(Serialize)]
+    struct Wrapper {
+        value: Value,
+    }
+
+    Wrapper { value: Value::Null }.serialize(serializer)
+}
+
+fn from_value<'de, D, T>(deserializer: D) -> Result<T, D::Error>
+where
+    D: Deserializer<'de>,
+    T: serde::de::DeserializeOwned,
+    T: std::fmt::Debug,
+{
+    #[derive(Debug, Deserialize)]
+    struct Wrapper<T> {
+        value: T,
+    }
+
+    let v = Value::deserialize(deserializer)?;
+    if v.is_object() {
+        let w = serde_json::from_value::<Wrapper<T>>(v).map_err(de::Error::custom)?;
+        Ok(w.value)
+    } else {
+        Err(de::Error::custom("Cannot be deserialized to struct"))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::test::{assert_de, assert_ser_de, ELEMENT_KEY};
+    use serde_json::json;
+
+    #[test]
+    fn test_boolean_response() {
+        assert_ser_de(&MarionetteResult::Bool(true), json!({"value": true}));
+    }
+
+    #[test]
+    fn test_cookies_response() {
+        let mut data = Vec::new();
+        data.push(Cookie {
+            name: "foo".into(),
+            value: "bar".into(),
+            path: Some("/common".into()),
+            domain: Some("web-platform.test".into()),
+            secure: false,
+            http_only: false,
+            expiry: None,
+            same_site: Some("Strict".into()),
+        });
+        assert_ser_de(
+            &MarionetteResult::Cookies(data),
+            json!([{"name":"foo","value":"bar","path":"/common","domain":"web-platform.test","secure":false,"httpOnly":false,"sameSite":"Strict"}]),
+        );
+    }
+
+    #[test]
+    fn test_new_window_response() {
+        let data = NewWindow {
+            handle: "6442450945".into(),
+            type_hint: "tab".into(),
+        };
+        let json = json!({"handle": "6442450945", "type": "tab"});
+        assert_ser_de(&MarionetteResult::NewWindow(data), json);
+    }
+
+    #[test]
+    fn test_web_element_response() {
+        let data = WebElement {
+            element: "foo".into(),
+        };
+        assert_ser_de(
+            &MarionetteResult::WebElement(data),
+            json!({"value": {ELEMENT_KEY: "foo"}}),
+        );
+    }
+
+    #[test]
+    fn test_web_elements_response() {
+        let data = vec![
+            WebElement {
+                element: "foo".into(),
+            },
+            WebElement {
+                element: "bar".into(),
+            },
+        ];
+        assert_ser_de(
+            &MarionetteResult::WebElements(data),
+            json!([{ELEMENT_KEY: "foo"}, {ELEMENT_KEY: "bar"}]),
+        );
+    }
+
+    #[test]
+    fn test_timeouts_response() {
+        let data = Timeouts {
+            implicit: Some(1000),
+            page_load: Some(200000),
+            script: Some(Some(60000)),
+        };
+        assert_ser_de(
+            &MarionetteResult::Timeouts(data),
+            json!({"implicit":1000,"pageLoad":200000,"script":60000}),
+        );
+    }
+
+    #[test]
+    fn test_string_response() {
+        assert_ser_de(
+            &MarionetteResult::String("foo".into()),
+            json!({"value": "foo"}),
+        );
+    }
+
+    #[test]
+    fn test_strings_response() {
+        assert_ser_de(
+            &MarionetteResult::Strings(vec!["2147483649".to_string()]),
+            json!(["2147483649"]),
+        );
+    }
+
+    #[test]
+    fn test_null_response() {
+        assert_ser_de(&MarionetteResult::Null, json!({ "value": null }));
+    }
+
+    #[test]
+    fn test_window_rect_response() {
+        let data = WindowRect {
+            x: 100,
+            y: 100,
+            width: 800,
+            height: 600,
+        };
+        let json = json!({"x": 100, "y": 100, "width": 800, "height": 600});
+        assert_ser_de(&MarionetteResult::WindowRect(data), json);
+    }
+
+    #[test]
+    fn test_element_rect_response() {
+        let data = ElementRect {
+            x: 8.0,
+            y: 8.0,
+            width: 148.6666717529297,
+            height: 22.0,
+        };
+        let json = json!({"x": 8, "y": 8, "width": 148.6666717529297, "height": 22});
+        assert_de(&MarionetteResult::ElementRect(data), json);
+    }
+}
diff --git a/testing/geckodriver/marionette/src/test.rs b/testing/geckodriver/marionette/src/test.rs
new file mode 100644
index 0000000000..3b20bb0917
--- /dev/null
+++ b/testing/geckodriver/marionette/src/test.rs
@@ -0,0 +1,35 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+pub static ELEMENT_KEY: &'static str = "element-6066-11e4-a52e-4f735466cecf";
+
+pub fn assert_ser_de<T>(data: &T, json: serde_json::Value)
+where
+    T: std::fmt::Debug,
+    T: std::cmp::PartialEq,
+    T: serde::de::DeserializeOwned,
+    T: serde::Serialize,
+{
+    assert_eq!(serde_json::to_value(data).unwrap(), json);
+    assert_eq!(data, &serde_json::from_value::<T>(json).unwrap());
+}
+
+#[allow(dead_code)]
+pub fn assert_ser<T>(data: &T, json: serde_json::Value)
+where
+    T: std::fmt::Debug,
+    T: std::cmp::PartialEq,
+    T: serde::Serialize,
+{
+    assert_eq!(serde_json::to_value(data).unwrap(), json);
+}
+
+pub fn assert_de<T>(data: &T, json: serde_json::Value)
+where
+    T: std::fmt::Debug,
+    T: std::cmp::PartialEq,
+    T: serde::de::DeserializeOwned,
+{
+    assert_eq!(data, &serde_json::from_value::<T>(json).unwrap());
+}
diff --git a/testing/geckodriver/marionette/src/webdriver.rs b/testing/geckodriver/marionette/src/webdriver.rs
new file mode 100644
index 0000000000..a795701198
--- /dev/null
+++ b/testing/geckodriver/marionette/src/webdriver.rs
@@ -0,0 +1,459 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+
+use crate::common::{from_cookie, from_name, to_cookie, to_name, Cookie, Frame, Timeouts, Window};
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct Url {
+    pub url: String,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct LegacyWebElement {
+    pub id: String,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct Locator {
+    pub using: Selector,
+    pub value: String,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub enum Selector {
+    #[serde(rename = "css selector")]
+    Css,
+    #[serde(rename = "link text")]
+    LinkText,
+    #[serde(rename = "partial link text")]
+    PartialLinkText,
+    #[serde(rename = "tag name")]
+    TagName,
+    #[serde(rename = "xpath")]
+    XPath,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct NewWindow {
+    #[serde(rename = "type", skip_serializing_if = "Option::is_none")]
+    pub type_hint: Option<String>,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct WindowRect {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub x: Option<i32>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub y: Option<i32>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub width: Option<i32>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub height: Option<i32>,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct Keys {
+    pub text: String,
+    pub value: Vec<String>,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(default, rename_all = "camelCase")]
+pub struct PrintParameters {
+    pub orientation: PrintOrientation,
+    pub scale: f64,
+    pub background: bool,
+    pub page: PrintPage,
+    pub margin: PrintMargins,
+    pub page_ranges: Vec<String>,
+    pub shrink_to_fit: bool,
+}
+
+impl Default for PrintParameters {
+    fn default() -> Self {
+        PrintParameters {
+            orientation: PrintOrientation::default(),
+            scale: 1.0,
+            background: false,
+            page: PrintPage::default(),
+            margin: PrintMargins::default(),
+            page_ranges: Vec::new(),
+            shrink_to_fit: true,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum PrintOrientation {
+    Landscape,
+    Portrait,
+}
+
+impl Default for PrintOrientation {
+    fn default() -> Self {
+        PrintOrientation::Portrait
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct PrintPage {
+    pub width: f64,
+    pub height: f64,
+}
+
+impl Default for PrintPage {
+    fn default() -> Self {
+        PrintPage {
+            width: 21.59,
+            height: 27.94,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct PrintMargins {
+    pub top: f64,
+    pub bottom: f64,
+    pub left: f64,
+    pub right: f64,
+}
+
+impl Default for PrintMargins {
+    fn default() -> Self {
+        PrintMargins {
+            top: 1.0,
+            bottom: 1.0,
+            left: 1.0,
+            right: 1.0,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct ScreenshotOptions {
+    pub id: Option<String>,
+    pub highlights: Vec<Option<String>>,
+    pub full: bool,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct Script {
+    pub script: String,
+    pub args: Option<Vec<Value>>,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub enum Command {
+    #[serde(rename = "WebDriver:AcceptAlert")]
+    AcceptAlert,
+    #[serde(
+        rename = "WebDriver:AddCookie",
+        serialize_with = "to_cookie",
+        deserialize_with = "from_cookie"
+    )]
+    AddCookie(Cookie),
+    #[serde(rename = "WebDriver:CloseWindow")]
+    CloseWindow,
+    #[serde(
+        rename = "WebDriver:DeleteCookie",
+        serialize_with = "to_name",
+        deserialize_with = "from_name"
+    )]
+    DeleteCookie(String),
+    #[serde(rename = "WebDriver:DeleteAllCookies")]
+    DeleteCookies,
+    #[serde(rename = "WebDriver:DeleteSession")]
+    DeleteSession,
+    #[serde(rename = "WebDriver:DismissAlert")]
+    DismissAlert,
+    #[serde(rename = "WebDriver:ElementClear")]
+    ElementClear(LegacyWebElement),
+    #[serde(rename = "WebDriver:ElementClick")]
+    ElementClick(LegacyWebElement),
+    #[serde(rename = "WebDriver:ElementSendKeys")]
+    ElementSendKeys {
+        id: String,
+        text: String,
+        value: Vec<String>,
+    },
+    #[serde(rename = "WebDriver:ExecuteAsyncScript")]
+    ExecuteAsyncScript(Script),
+    #[serde(rename = "WebDriver:ExecuteScript")]
+    ExecuteScript(Script),
+    #[serde(rename = "WebDriver:FindElement")]
+    FindElement(Locator),
+    #[serde(rename = "WebDriver:FindElements")]
+    FindElements(Locator),
+    #[serde(rename = "WebDriver:FindElement")]
+    FindElementElement {
+        element: String,
+        using: Selector,
+        value: String,
+    },
+    #[serde(rename = "WebDriver:FindElements")]
+    FindElementElements {
+        element: String,
+        using: Selector,
+        value: String,
+    },
+    #[serde(rename = "WebDriver:FullscreenWindow")]
+    FullscreenWindow,
+    #[serde(rename = "WebDriver:Navigate")]
+    Get(Url),
+    #[serde(rename = "WebDriver:GetActiveElement")]
+    GetActiveElement,
+    #[serde(rename = "WebDriver:GetAlertText")]
+    GetAlertText,
+    #[serde(rename = "WebDriver:GetCookies")]
+    GetCookies,
+    #[serde(rename = "WebDriver:GetElementCSSValue")]
+    GetCSSValue {
+        id: String,
+        #[serde(rename = "propertyName")]
+        property: String,
+    },
+    #[serde(rename = "WebDriver:GetCurrentURL")]
+    GetCurrentUrl,
+    #[serde(rename = "WebDriver:GetElementAttribute")]
+    GetElementAttribute { id: String, name: String },
+    #[serde(rename = "WebDriver:GetElementProperty")]
+    GetElementProperty { id: String, name: String },
+    #[serde(rename = "WebDriver:GetElementRect")]
+    GetElementRect(LegacyWebElement),
+    #[serde(rename = "WebDriver:GetElementTagName")]
+    GetElementTagName(LegacyWebElement),
+    #[serde(rename = "WebDriver:GetElementText")]
+    GetElementText(LegacyWebElement),
+    #[serde(rename = "WebDriver:GetPageSource")]
+    GetPageSource,
+    #[serde(rename = "WebDriver:GetShadowRoot")]
+    GetShadowRoot { id: String },
+    #[serde(rename = "WebDriver:GetTimeouts")]
+    GetTimeouts,
+    #[serde(rename = "WebDriver:GetTitle")]
+    GetTitle,
+    #[serde(rename = "WebDriver:GetWindowHandle")]
+    GetWindowHandle,
+    #[serde(rename = "WebDriver:GetWindowHandles")]
+    GetWindowHandles,
+    #[serde(rename = "WebDriver:GetWindowRect")]
+    GetWindowRect,
+    #[serde(rename = "WebDriver:Back")]
+    GoBack,
+    #[serde(rename = "WebDriver:Forward")]
+    GoForward,
+    #[serde(rename = "WebDriver:IsElementDisplayed")]
+    IsDisplayed(LegacyWebElement),
+    #[serde(rename = "WebDriver:IsElementEnabled")]
+    IsEnabled(LegacyWebElement),
+    #[serde(rename = "WebDriver:IsElementSelected")]
+    IsSelected(LegacyWebElement),
+    #[serde(rename = "WebDriver:MaximizeWindow")]
+    MaximizeWindow,
+    #[serde(rename = "WebDriver:MinimizeWindow")]
+    MinimizeWindow,
+    #[serde(rename = "WebDriver:NewWindow")]
+    NewWindow(NewWindow),
+    #[serde(rename = "WebDriver:Print")]
+    Print(PrintParameters),
+    #[serde(rename = "WebDriver:Refresh")]
+    Refresh,
+    #[serde(rename = "WebDriver:ReleaseActions")]
+    ReleaseActions,
+    #[serde(rename = "WebDriver:SendAlertText")]
+    SendAlertText(Keys),
+    #[serde(rename = "WebDriver:SetTimeouts")]
+    SetTimeouts(Timeouts),
+    #[serde(rename = "WebDriver:SetWindowRect")]
+    SetWindowRect(WindowRect),
+    #[serde(rename = "WebDriver:SwitchToFrame")]
+    SwitchToFrame(Frame),
+    #[serde(rename = "WebDriver:SwitchToParentFrame")]
+    SwitchToParentFrame,
+    #[serde(rename = "WebDriver:SwitchToWindow")]
+    SwitchToWindow(Window),
+    #[serde(rename = "WebDriver:TakeScreenshot")]
+    TakeElementScreenshot(ScreenshotOptions),
+    #[serde(rename = "WebDriver:TakeScreenshot")]
+    TakeFullScreenshot(ScreenshotOptions),
+    #[serde(rename = "WebDriver:TakeScreenshot")]
+    TakeScreenshot(ScreenshotOptions),
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::common::Date;
+    use crate::test::{assert_ser, assert_ser_de};
+    use serde_json::json;
+
+    #[test]
+    fn test_json_screenshot() {
+        let data = ScreenshotOptions {
+            id: None,
+            highlights: vec![],
+            full: false,
+        };
+        let json = json!({"full":false,"highlights":[],"id":null});
+        assert_ser_de(&data, json);
+    }
+
+    #[test]
+    fn test_json_selector_css() {
+        assert_ser_de(&Selector::Css, json!("css selector"));
+    }
+
+    #[test]
+    fn test_json_selector_link_text() {
+        assert_ser_de(&Selector::LinkText, json!("link text"));
+    }
+
+    #[test]
+    fn test_json_selector_partial_link_text() {
+        assert_ser_de(&Selector::PartialLinkText, json!("partial link text"));
+    }
+
+    #[test]
+    fn test_json_selector_tag_name() {
+        assert_ser_de(&Selector::TagName, json!("tag name"));
+    }
+
+    #[test]
+    fn test_json_selector_xpath() {
+        assert_ser_de(&Selector::XPath, json!("xpath"));
+    }
+
+    #[test]
+    fn test_json_selector_invalid() {
+        assert!(serde_json::from_value::<Selector>(json!("foo")).is_err());
+    }
+
+    #[test]
+    fn test_json_locator() {
+        let json = json!({
+            "using": "partial link text",
+            "value": "link text",
+        });
+        let data = Locator {
+            using: Selector::PartialLinkText,
+            value: "link text".into(),
+        };
+
+        assert_ser_de(&data, json);
+    }
+
+    #[test]
+    fn test_json_keys() {
+        let data = Keys {
+            text: "Foo".into(),
+            value: vec!["F".into(), "o".into(), "o".into()],
+        };
+        let json = json!({"text": "Foo", "value": ["F", "o", "o"]});
+        assert_ser_de(&data, json);
+    }
+
+    #[test]
+    fn test_json_new_window() {
+        let data = NewWindow {
+            type_hint: Some("foo".into()),
+        };
+        assert_ser_de(&data, json!({ "type": "foo" }));
+    }
+
+    #[test]
+    fn test_json_window_rect() {
+        let data = WindowRect {
+            x: Some(123),
+            y: None,
+            width: None,
+            height: None,
+        };
+        assert_ser_de(&data, json!({"x": 123}));
+    }
+
+    #[test]
+    fn test_command_with_params() {
+        let locator = Locator {
+            using: Selector::Css,
+            value: "value".into(),
+        };
+        let json = json!({"WebDriver:FindElement": {"using": "css selector", "value": "value"}});
+        assert_ser_de(&Command::FindElement(locator), json);
+    }
+
+    #[test]
+    fn test_command_with_wrapper_params() {
+        let cookie = Cookie {
+            name: "hello".into(),
+            value: "world".into(),
+            path: None,
+            domain: None,
+            secure: false,
+            http_only: false,
+            expiry: Some(Date(1564488092)),
+            same_site: None,
+        };
+        let json = json!({"WebDriver:AddCookie": {"cookie": {"name": "hello", "value": "world", "secure": false, "httpOnly": false, "expiry": 1564488092}}});
+        assert_ser_de(&Command::AddCookie(cookie), json);
+    }
+
+    #[test]
+    fn test_empty_commands() {
+        assert_ser_de(&Command::GetTimeouts, json!("WebDriver:GetTimeouts"));
+    }
+
+    #[test]
+    fn test_json_command_invalid() {
+        assert!(serde_json::from_value::<Command>(json!("foo")).is_err());
+    }
+
+    #[test]
+    fn test_json_delete_cookie_command() {
+        let json = json!({"WebDriver:DeleteCookie": {"name": "foo"}});
+        assert_ser_de(&Command::DeleteCookie("foo".into()), json);
+    }
+
+    #[test]
+    fn test_json_new_window_command() {
+        let data = NewWindow {
+            type_hint: Some("foo".into()),
+        };
+        let json = json!({"WebDriver:NewWindow": {"type": "foo"}});
+        assert_ser_de(&Command::NewWindow(data), json);
+    }
+
+    #[test]
+    fn test_json_new_window_command_with_none_value() {
+        let data = NewWindow { type_hint: None };
+        let json = json!({"WebDriver:NewWindow": {}});
+        assert_ser_de(&Command::NewWindow(data), json);
+    }
+
+    #[test]
+    fn test_json_command_as_struct() {
+        assert_ser(
+            &Command::FindElementElement {
+                element: "foo".into(),
+                using: Selector::XPath,
+                value: "bar".into(),
+            },
+            json!({"WebDriver:FindElement": {"element": "foo", "using": "xpath", "value": "bar" }}),
+        );
+    }
+
+    #[test]
+    fn test_json_get_css_value() {
+        assert_ser_de(
+            &Command::GetCSSValue {
+                id: "foo".into(),
+                property: "bar".into(),
+            },
+            json!({"WebDriver:GetElementCSSValue": {"id": "foo", "propertyName": "bar"}}),
+        );
+    }
+}