diff --git a/testing/marionette/test_error.js b/testing/marionette/test_error.js
new file mode 100644
index 000000000000..5d9dbca532e2
--- /dev/null
+++ b/testing/marionette/test_error.js
@@ -0,0 +1,278 @@
+/* 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/. */
+
+const {utils: Cu} = Components;
+
+Cu.import("chrome://marionette/content/error.js");
+
+function run_test() {
+  run_next_test();
+}
+
+function notok(condition) {
+  ok(!(condition));
+}
+
+add_test(function test_isError() {
+  notok(error.isError(null));
+  notok(error.isError([]));
+  notok(error.isError(new Date()));
+
+  ok(error.isError(new Components.Exception()));
+  ok(error.isError(new Error()));
+  ok(error.isError(new WebDriverError()));
+  ok(error.isError(new InvalidArgumentError()));
+
+  run_next_test();
+});
+
+add_test(function test_isWebDriverError() {
+  notok(error.isWebDriverError(new Components.Exception()));
+  notok(error.isWebDriverError(new Error()));
+
+  ok(error.isWebDriverError(new WebDriverError()));
+  ok(error.isWebDriverError(new InvalidArgumentError()));
+
+  run_next_test();
+});
+
+add_test(function test_stringify() {
+  equal("<unprintable error>", error.stringify());
+  equal("<unprintable error>", error.stringify("foo"));
+  equal("[object Object]", error.stringify({}));
+  equal("[object Object]\nfoo", error.stringify({stack: "foo"}));
+  equal("Error: foo", error.stringify(new Error("foo")).split("\n")[0]);
+  equal("WebDriverError: foo",
+      error.stringify(new WebDriverError("foo")).split("\n")[0]);
+  equal("InvalidArgumentError: foo",
+      error.stringify(new InvalidArgumentError("foo")).split("\n")[0]);
+
+  run_next_test();
+});
+
+add_test(function test_toJson() {
+  deepEqual({error: "a", message: null, stacktrace: null},
+      error.toJson({status: "a"}));
+  deepEqual({error: "a", message: "b", stacktrace: null},
+      error.toJson({status: "a", message: "b"}));
+  deepEqual({error: "a", message: "b", stacktrace: "c"},
+      error.toJson({status: "a", message: "b", stack: "c"}));
+
+  let e1 = new Error("b");
+  deepEqual({error: undefined, message: "b", stacktrace: e1.stack},
+      error.toJson(e1));
+  let e2 = new WebDriverError("b");
+  deepEqual({error: e2.status, message: "b", stacktrace: null},
+      error.toJson(e2));
+
+  run_next_test();
+});
+
+add_test(function test_WebDriverError() {
+  let err = new WebDriverError("foo");
+  equal("WebDriverError", err.name);
+  equal("foo", err.message);
+  equal("webdriver error", err.status);
+  equal(Error.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_ElementNotAccessibleError() {
+  let err = new ElementNotAccessibleError("foo");
+  equal("ElementNotAccessibleError", err.name);
+  equal("foo", err.message);
+  equal("element not accessible", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_ElementNotVisibleError() {
+  let err = new ElementNotVisibleError("foo");
+  equal("ElementNotVisibleError", err.name);
+  equal("foo", err.message);
+  equal("element not visible", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_InvalidArgumentError() {
+  let err = new InvalidArgumentError("foo");
+  equal("InvalidArgumentError", err.name);
+  equal("foo", err.message);
+  equal("invalid argument", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_InvalidElementStateError() {
+  let err = new InvalidElementStateError("foo");
+  equal("InvalidElementStateError", err.name);
+  equal("foo", err.message);
+  equal("invalid element state", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_InvalidSelectorError() {
+  let err = new InvalidSelectorError("foo");
+  equal("InvalidSelectorError", err.name);
+  equal("foo", err.message);
+  equal("invalid selector", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_InvalidSessionIdError() {
+  let err = new InvalidSessionIdError("foo");
+  equal("InvalidSessionIdError", err.name);
+  equal("foo", err.message);
+  equal("invalid session id", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_JavaScriptError() {
+  let err = new JavaScriptError("foo");
+  equal("JavaScriptError", err.name);
+  equal("foo", err.message);
+  equal("javascript error", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  equal("undefined", new JavaScriptError(undefined).message);
+  // TODO(ato): Bug 1240550
+  //equal("funcname @file", new JavaScriptError("message", "funcname", "file").stack);
+  equal("funcname @file, line line",
+      new JavaScriptError("message", "funcname", "file", "line").stack);
+
+  // TODO(ato): More exhaustive tests for JS stack computation
+
+  run_next_test();
+});
+
+add_test(function test_NoAlertOpenError() {
+  let err = new NoAlertOpenError("foo");
+  equal("NoAlertOpenError", err.name);
+  equal("foo", err.message);
+  equal("no such alert", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_NoSuchElementError() {
+  let err = new NoSuchElementError("foo");
+  equal("NoSuchElementError", err.name);
+  equal("foo", err.message);
+  equal("no such element", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_NoSuchFrameError() {
+  let err = new NoSuchFrameError("foo");
+  equal("NoSuchFrameError", err.name);
+  equal("foo", err.message);
+  equal("no such frame", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_NoSuchWindowError() {
+  let err = new NoSuchWindowError("foo");
+  equal("NoSuchWindowError", err.name);
+  equal("foo", err.message);
+  equal("no such window", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_ScriptTimeoutError() {
+  let err = new ScriptTimeoutError("foo");
+  equal("ScriptTimeoutError", err.name);
+  equal("foo", err.message);
+  equal("script timeout", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_SessionNotCreatedError() {
+  let err = new SessionNotCreatedError("foo");
+  equal("SessionNotCreatedError", err.name);
+  equal("foo", err.message);
+  equal("session not created", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_StaleElementReferenceError() {
+  let err = new StaleElementReferenceError("foo");
+  equal("StaleElementReferenceError", err.name);
+  equal("foo", err.message);
+  equal("stale element reference", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_TimeoutError() {
+  let err = new TimeoutError("foo");
+  equal("TimeoutError", err.name);
+  equal("foo", err.message);
+  equal("timeout", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_UnableToSetCookieError() {
+  let err = new UnableToSetCookieError("foo");
+  equal("UnableToSetCookieError", err.name);
+  equal("foo", err.message);
+  equal("unable to set cookie", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_UnknownCommandError() {
+  let err = new UnknownCommandError("foo");
+  equal("UnknownCommandError", err.name);
+  equal("foo", err.message);
+  equal("unknown command", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_UnknownError() {
+  let err = new UnknownError("foo");
+  equal("UnknownError", err.name);
+  equal("foo", err.message);
+  equal("unknown error", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});
+
+add_test(function test_UnsupportedOperationError() {
+  let err = new UnsupportedOperationError("foo");
+  equal("UnsupportedOperationError", err.name);
+  equal("foo", err.message);
+  equal("unsupported operation", err.status);
+  equal(WebDriverError.prototype.toString(), Object.getPrototypeOf(err).toString());
+
+  run_next_test();
+});