--- a/testing/marionette/driver.js
+++ b/testing/marionette/driver.js
@@ -133,18 +133,17 @@ this.GeckoDriver = function(appId, serve
   // topmost chrome frame
   this.mainFrame = null;
   // chrome iframe that currently has focus
   this.curFrame = null;
   this.currentFrameElement = null;
   this.observing = null;
   this._browserIds = new WeakMap();
 
-  // The curent context decides if commands should affect chrome- or
-  // content space.
+  // Use content context by default
   this.context = Context.Content;
 
   this.sandboxes = new Sandboxes(() => this.getCurrentWindow());
   this.legacyactions = new legacyaction.Chain();
 
   this.capabilities = new session.Capabilities();
 
   this.mm = globalMessageManager;
@@ -158,16 +157,30 @@ this.GeckoDriver = function(appId, serve
 
 Object.defineProperty(GeckoDriver.prototype, "a11yChecks", {
   get() {
     return this.capabilities.get("moz:accessibilityChecks");
   },
 });
 
 /**
+ * The current context decides if commands are executed in chrome- or
+ * content space.
+ */
+Object.defineProperty(GeckoDriver.prototype, "context", {
+  get() {
+    return this._context;
+  },
+
+  set(context) {
+    this._context = Context.fromString(context);
+  },
+});
+
+/**
  * Returns the current URL of the ChromeWindow or content browser,
  * depending on context.
  *
  * @return {URL}
  *     Read-only property containing the currently loaded URL.
  */
 Object.defineProperty(GeckoDriver.prototype, "currentURL", {
   get() {
@@ -795,17 +808,18 @@ GeckoDriver.prototype.getSessionCapabili
  *
  * @throws {InvalidArgumentError}
  *     If <var>value</var> is not a string.
  * @throws {WebDriverError}
  *     If <var>value</var> is not a valid browsing context.
  */
 GeckoDriver.prototype.setContext = function(cmd) {
   let value = assert.string(cmd.parameters.value);
-  this.context = Context.fromString(value);
+
+  this.context = value;
 };
 
 /**
  * Gets the context type that is Marionette's current target for
  * browsing context scoped commands.
  *
  * You may choose a context through the {@link #setContext} command.
  *

rename from testing/marionette/harness/marionette_harness/tests/unit/test_with_using_context.py
rename to testing/marionette/harness/marionette_harness/tests/unit/test_context.py
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_with_using_context.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_context.py
@@ -1,35 +1,52 @@
 # 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/.
 
 from __future__ import absolute_import
 
 from marionette_driver.decorators import using_context
 from marionette_driver.errors import MarionetteException
-
 from marionette_harness import MarionetteTestCase
 
 
-class TestSetContext(MarionetteTestCase):
+class ContextTestCase(MarionetteTestCase):
+
     def setUp(self):
-        MarionetteTestCase.setUp(self)
+        super(ContextTestCase, self).setUp()
 
         # shortcuts to improve readability of these tests
         self.chrome = self.marionette.CONTEXT_CHROME
         self.content = self.marionette.CONTEXT_CONTENT
 
+        self.assertEquals(self.get_context(), self.content)
+
         test_url = self.marionette.absolute_url("empty.html")
         self.marionette.navigate(test_url)
+
+    def get_context(self):
+        return self.marionette._send_message("getContext", key="value")
+
+
+class TestSetContext(ContextTestCase):
+
+    def test_switch_context(self):
+        self.marionette.set_context(self.chrome)
+        self.assertEquals(self.get_context(), self.chrome)
+
         self.marionette.set_context(self.content)
         self.assertEquals(self.get_context(), self.content)
 
-    def get_context(self):
-        return self.marionette._send_message("getContext", key="value")
+    def test_invalid_context(self):
+        with self.assertRaises(ValueError):
+            self.marionette.set_context("foobar")
+
+
+class TestUsingContext(ContextTestCase):
 
     def test_set_different_context_using_with_block(self):
         with self.marionette.using_context(self.chrome):
             self.assertEquals(self.get_context(), self.chrome)
         self.assertEquals(self.get_context(), self.content)
 
     def test_set_same_context_using_with_block(self):
         with self.marionette.using_context(self.content):
@@ -56,13 +73,15 @@ class TestSetContext(MarionetteTestCase)
             with self.marionette.using_context(self.chrome):
                 raise MarionetteException
         self.assertEquals(self.get_context(), self.content)
 
     def test_with_using_context_decorator(self):
         @using_context('content')
         def inner_content(m):
             self.assertEquals(self.get_context(), 'content')
+
         @using_context('chrome')
         def inner_chrome(m):
             self.assertEquals(self.get_context(), 'chrome')
+
         inner_content(self.marionette)
         inner_chrome(self.marionette)

--- a/testing/marionette/harness/marionette_harness/tests/unit/unit-tests.ini
+++ b/testing/marionette/harness/marionette_harness/tests/unit/unit-tests.ini
@@ -90,17 +90,17 @@ skip-if = true # Bug 925688
 [test_errors.py]
 
 [test_execute_isolate.py]
 [test_click_scrolling.py]
 [test_profile_management.py]
 skip-if = manage_instance == false || appname == 'fennec' # Bug 1298921
 [test_quit_restart.py]
 skip-if = manage_instance == false || appname == 'fennec' # Bug 1298921
-[test_with_using_context.py]
+[test_context.py]
 
 [test_modal_dialogs.py]
 skip-if = appname == 'fennec' # Bug 1325738
 [test_key_actions.py]
 [test_legacy_mouse_action.py]
 skip-if = appname == 'fennec'
 [test_mouse_action.py]
 skip-if = appname == 'fennec'