Mockery: generate Google Mock class from C++ interfaces

Building the project

1. Make sure libclang is installed in the library search path:

• On Ubuntu, install it using sudo apt install libclang-dev
• On macOS, install Xcode development tools and set DYLD_LIBRARY_PATH=/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib in your environment.

2. cargo build

Creating a mock class for the example C++ project

The example directory contains a simple CMake project which itself deal in some sort of fictional Project class which might represent an IDE project for instance. Projects are persisted to disk through an interface called ProjectStorage. A implementation FilesystemProjectStorage exists and is injected into the Project in production but is unsuitable for testing the Project unit as filesystem operations quickly cause tests to become flakey. Thanks to the dependency injection, we can test Project by mocking ProjectStorage.

To create the mock implementation using Mockery, we first configure the CMake project using

$ cmake -G Ninja -S example -B example/cmake-build-debug

The example is already set up to create a compile commands database. To do in your own projects, pass -DCMAKE_EXPORT_COMPILE_COMMANDS=ON as an additional argument.

Mockery will try to locate the compile commands database in relation to the project sources automatically. You only need to specify the name of the interface that should be mocked, in this case ProjectStorage. The definition of the mock class will be written to standard out for now:

$ cargo run -- create example/src/project/Project.cpp -i ProjectStorage

struct ProjectStorageMock : ProjectStorage {
    MOCK_METHOD(bool, Open, (std::string_view), (override));
    MOCK_METHOD(bool, Close, (), (override));
    MOCK_METHOD(bool, IsOpen, (), (const, noexcept, override));
    MOCK_METHOD((std::map<std::string, Type>), List, (), (const, override));
    MOCK_METHOD(std::string, ReadFile, (std::string_view), (const, override));
    MOCK_METHOD(void, SaveFile, (std::string_view, std::string const&), (override));
};