Scopes tutorials - unit testing

In this tutorial you will learn how to write a unit test to strengthen the quality of your Ubuntu scope. It builds upon the scopes development tutorials.


  • Ubuntu 14.10 or later
    Get Ubuntu
  • The scopes development tutorial
    If you haven't already, complete the scopes tutorials.
  • googletest
    Since you need to build the library from source, you'll notice we install make and cmake. Open a terminal with Ctrl+Alt+T and run these commands to install all required packages:
$ sudo apt-get install libgtest-dev google-mock make cmake

What are unit tests?

To help ensure your application performs as expected it’s important to have a nice suite of unit tests. Unit tests are the foundation of a good testing story for your application. Let’s learn more about them.

A unit test should generally test a specific unit of code. It should be able to pass or fail in only one way. This means you should generally have one and only one assertion or assert for short. An assertion is a statement about the expected outcome of a series of actions. By limiting yourself to a single statement about the expected outcome, it is clear why a test fails.

Unit tests are the base of the . The testing pyramid describes the three levels of testing an application, going from low level tests at the bottom and increasing to high level tests at the top. As unit tests are the lowest level, they should represent the largest number of tests for your project.

In Ubuntu, unit tests for your scope:

  • Are written in C++, just like the scope
  • Utilize googletest and googlemock

Testing with googletest and googlemock

Before we can begin writing tests we need to build the googletest library and copy it for usage. Run the following commands one line at a time from the terminal:

$ mkdir /tmp/build && cd /tmp/build
$ cmake -DCMAKE_BUILD_TYPE=RELEASE /usr/src/gtest/
$ make
$ sudo cp libg*.a /usr/lib/

This will take a minute to build on your machine and should complete without error.

An example testcase

A basic testcase is very simple.

  • Declare a TEST() function. It shouldn't return a value.
  • Add some C++ code to perform actions
  • Use assertions to check the values
TEST(testcase, test) {
    ACTION . . .
    EXPECT . . .

The list of valid assertions includes asserting for true or false, equals or not equals, etc. Googletest has the full list ofassertions.

For example, here's a simple test suite for a function which reverses a string:

void reverse(std::string &string) {
    std::reverse(string.begin(), string.end());
TEST(test_reverse, reverse_single_character) {
    EXPECT_EQ('t', 't');
TEST(test_reverse, reverse_word) {
    EXPECT_EQ('at', 'ta');

Test Helpers

The testing helper classes are in the unity::scopes::testing namespace. The most important ones are:

  • unity::scopes::testing::TypedScopeFixture
    • A template class that takes your scope class name as a template argument and creates a test fixture that can be used in tests.
  • unity::scopes::testing::MockSearchReply
    • A mock of unity::scopes::SearchReply that makes it possible to intercept responses to search request sent from the scope to a client, so you can test if your scope returns the expected data.
  • unity::scopes::testing::MockPreviewReply
    • A mock of unity::scopes::PreviewReply that makes it possible to intercept and test responses to preview request sent from the scope to a client.
  • unity::scopes::testing::Result
    • A simple Result class derived from unity::scopes::Result that provides a default constructor, so you can create dummy results (without attributes) for testing purposes.
  • unity::scopes::testing::category
    • A simple class derived from unity::scopes::Category that makes it possible to create dummy categories (which otherwise would require an instance of SearchReply and a call to register_category()).

Test Template

For scope unit tests, most will share a basic structure, as follows:

TEST_F(TestScope, empty_search_string) {
   const unity::scopes::CategoryRenderer renderer;
   NiceMock reply;

   // Build a query with an empty search string
   unity::scopes::CannedQuery query(SCOPE_NAME, "", "");

   // Tests will typically go here //
   unity::scopes::SearchReplyProxy reply_proxy(&reply, [](sc::SearchReply*) {});     
   unity::scopes::SearchMetadata meta_data("en_US", "phone");

   // Create a query object
   auto search_query = scope->search(query, meta_data);
   ASSERT_NE(nullptr, search_query);

   // Run the search

   // Google Mock will make assertions when the mocks are destructed.

This template sets up a mocked SearchReply object which will be our primary way of getting test results (see below). It then creates and runs a query using our scope and query code. Test assertions will be evaluated once everything is finished.


The first thing to do when writing a unit test is to decide what conditions describe success. When testing scopes using the Google Test framework this is most commonly done using the EXPECT_CALL assertion.

EXPECT_CALL is a macro which returns success or a nonfatal failure (meaning the test will continue and potentially multiple failures can be reported in a single run) depending on whether a certain function call is made.

Typically, an EXPECT_CALL invocation will look like the following:

EXPECT_CALL(reply, register_category("A", "", "", _)).Times(1)
.WillOnce(Return(make_shared("A", "", "", renderer)));

Here we are saying that our mocked reply (see above) should receive a call to register_category once (Times(1)) with the first parameter "A", the second and third empty strings, and a fourth with any value ('_' in this case means the value doesn't matter, don't consider it when determining whether this test passes or fails).

The second line is necessary because the scope will expect a return value from this call so we need to specify something for the MockSearchReply to return (in this case a mock Category). WillOnce is used because we expect only one call to this function with these parameters. You can also use WillRepeatedly if you expect that this function will be called multiple times (with the same unignored parameters).

Advanced Usage

Mocked classes

When writing a scope unit test you will want to exercise as much actual code in a scope as you can while mocking outside code to set up the conditions of the test. Google Mock provides a framework to do so easily and quickly. Additionally, the Unity Scopes API provides some very useful mock classes in the unity::scopes::testing namespace. In there you will find mock classes for Scope, Registry, SearchReply, and many others.

There is also a convenient scope test fixture class (TypedScopeFixture) which accepts your scope class as a template parameter and does much of the test setup for you:

typedef unity::scopes::testing::TypedScopeFixture<MyScope> TestScopeFixture;

If you need to do any additional setup, such as setting the scope directory to allow data files to be read, you can inherit from this class and override the SetUp() method:

class TestScope: public TypedScopeFixture {
   void SetUp() override

Note: Be sure to call the parent class SetUp() method as well!

Using Test Fixtures

Once your test fixture is set up you can begin writing tests that make use of it. There are two macros to use when writing tests, one for normal tests using the fixture (TEST_F) and one for parameterized tests (TEST_P).

Defining either one is simple, just specify the name of your fixture class and a name for the test:

TEST_F(TestScope, empty_search_string) { }

For a parameterized test, the definition is similar:

TEST_P(TestScope, all_the_things) { }

with the addition that you can run that test repeatedly with different parameters. To run the above example with every integer between 0 and 1023 you would use the following:

INSTANTIATE_TEST_CASE_P(all_the_things, TestScope,
                        ::testing::Range((unsigned int)0,
                        (unsigned int)(pow(2, 10))));

from within your test, use GetParam() to access the current value of the parameter for that run.

More examples of the types of parameters you can pass can be found in the Google Test documentation.

Custom Matchers

In order to facilitate checking that results and departments contain the data they should you can define custom “matchers” which can verify result properties or department structures.

A result matcher might look like the following:

MATCHER_P2(ResultProp, prop, value, "") {
   if (arg.contains(prop)) {
       *result_listener << "result[" << prop << "] is " << arg[prop].serialize_json();
   } else {
       *result_listener << "result[" << prop << "] is not set";
   return arg.contains(prop) && arg[prop] == Variant(value);

You can make use of this matcher as part of an EXPECT_CALL invocation:

EXPECT_CALL(reply, push(Matcher(AllOf(
       ResultProp("title", "Super awesome title"),
       ResultProp("uri", "")

This call will match the “title” and “uri” fields of a result against the supplied values. A department matcher could be defined like so:

MATCHER_P(IsDepartment, department, "") {
   return arg->serialize() == department->serialize();

To use this you would define a department structure using Department::create and add_subdepartment to match what you expect from your scope and use EXPECT_CALL to verify the match:

EXPECT_CALL(reply, register_departments(IsDepartment(departments))).Times(1);

Special Scopes

Aggregator Scopes

Mock Registry

The test fixture provided by the scopes SDK conveniently includes a mock scope registry. It is empty, however, which makes it less useful when testing aggregator scopes.

Since the leaf scopes won’t actually be running in the test environment we have to create mock scopes for each of them. This can be done easily with a function using unity::scopes::testing::ScopeMetadataBuilder:

unity::scopes::ScopeMetadata build_scope_metadata(string id)
   unity::scopes::testing::ScopeMetadataBuilder builder;
   return builder();

To populate your mock registry you can create a member in your scope fixture class of type unity::scopes::MetadataMap and fill it using:


For each scope you want in the registry. Then in your test have the list() method return your “filled” registry:

EXPECT_CALL(registry, list()).Times(1)

You can respond similarly to a get_metadata() call:

EXPECT_CALL(registry, get_metadata(SCOPE_ID)).Times(1)

Code Modifications to Support Mock Settings

The Scopes SDK is not set up to allow overriding of settings in a testing environment, so a bit of cheating is necessary to allow testing against different combinations of settings.

One simple way to do so is to add a test settings variable to your query (or scope if that’s where you access them) along with a setter method:

void MyQuery::set_test_settings(VariantMap const& settings)
   this->test_settings_ = settings;

Then you can “override” the settings() function to return the mock settings if they exist (which should only be true in a test environment) or the real settings otherwise:

VariantMap MyQuery::settings()
   if (test_settings_.empty())
       return QueryBase::settings();
       return test_settings_;

Since SearchQueryBase doesn’t have a set_test_settings() method, you can simply cast the search_query pointer’s target to your query class.

// Tell the query to use our mock settings
MyQuery *qry = static_cast(search_query.get());

Testing Settings Combinations

The simplest way to test every combination of settings is to set up a bit mask containing each of your settings and use a parameterized test to verify the behavior of your scope.

You’ll need your test fixture class to inherit from ::testing::WithParamInterface. As a concrete example let’s look at the News scope settings test. In this case I have an existing fixture class which does most of the setup for me, so I can inherit from that as well as the parameter interface class.

class SettingsTestScope : public TestScope,
                          public ::testing::WithParamInterface {
   void SetUp() override
       settings_bits_[FUN_ID] = 1;
       settings_bits_[CHEESE_ID]       = 1<<1;
       settings_bits_[NEWS_ID]  = 1<<2;
       settings_bits_[CHANNEL_ID]   = 1<<3;
       settings_bits_[SPORTS_ID]    = 1<<4;
       settings_bits_[SCOPE_ID] = 1<<5;
       settings_bits_[HOROSCOPE_ID]  = 1<<6;
       settings_bits_[BUSINESS_ID]      = 1<<7;
       settings_bits_[CONTENT_ID] = 1<<8;
       settings_bits_[FINANCE_ID]  = 1<<9;

You can see the bitmap with each subscope ID (which corresponds to whether each subscope is activated), and notice that we’ve set the parameter type to unsigned int.

Writing tests is as before, only you will use the TEST_P macro when defining them, telling Google Test that an extra parameter needs to be added to each test.

To access that parameter you can unsurprisingly use the GetParam() call. In our settings tests we will bitwise-AND our parameter with the bitmap we set up earlier to determine whether a scope should be accessed during this run. For example:

if (GetParam() & settings_bits_[FINANCE_ID]) {
    settings[FINANCE_ID] = true;
    // … tests for FINANCE_ID go here
} else {
    settings[FINANCE_ID] = false;

Repeat for each setting bit value.

Now to actually run these tests with different parameter values you can use the INSTANTIATE_TEST_CASE_P call shown above.

Testing Special Behavior (Online/Offline)

Some scope behavior depends on whether or not the device is online. In a normal running environment the online/offline state is set in the SearchMetadata by the shell. In a test environment this is not the case, so if your scope behaves differently with or without internet connectivity you need to specify which state you are testing by calling SearchMetadata::set_internet_connectivity before running your search.

You can set the connectivity state to connected:


or disconnected:


Generic Leaf Scopes

Mock Data Store

If your scope consumes data from some local storage you can use a similar technique to mock this data as in the settings. Add a field to your query along with a setter method, and conditionally use the mock data if it exists.


You've just learned how to write unit tests for a Ubuntu scope for the phone. But there is more information to be learned about how to write scope testing. Check out the links below for more documentation and help.