ccmock (Work in Progress)

Automatic mock creation for unit tests in C and C++.

Contents

• About
  • Motivation
  • Advantages
  • Disadvantages
• Features
• Installation
  • Supported Platforms
  • Required Programs
  • Dependencies
  • Procedure
• Usage
  • General Idea
  • Commands
    • Help Message
    • Write Mock Function to Standard Output
    • Write Mock Function to File
    • Using Compile Flags
    • Using a Compilation Database
    • Specifying Configuration Files
    • Dump Effective Configuration Settings
    • Pass Additional Compiler Flags to the Clang Frontend
  • Best Practices
• Examples
• Implementation Details
• Open Points

About

Motivation

Advantages

Disadvantages

ccmock either needs a compilation database or a compile_flags.txt to be able to parse a project's source files.

Features

• Automatic detection which functions need to be mocked.
• Blacklist entries
• Supported frameworks: * gmock * fff

Installation

Supported Platforms

• Arch Linux
• Fedora
• Ubuntu

Required Programs

Depending on which compiler you prefer, chose either * gcc 12.1.0 or * clang 14.0.0.

Also depending on what you prefer, chose either * make or * ninja 1.10.

In any case, you'll also need to following programs to build ccmock from source:

• bash
• cmake 3.24
• git

Dependencies

• llvm >= 14.0.0
• clang >= 14.0.0

Procedure

Install all required tools and libraries (chosing the most conservative options):

pacman -Syu llvm clang bash gcc git cmake make

apt-get install llvm llvm-dev clang libclang-dev bash gcc g++ git cmake make

Configure the build system:

cmake -B build -DCMAKE_BUILD_TYPE=release

Build the project with clang:

cmake --build build

Install the built program to /usr/local/bin:

cmake --install build --strip

Usage

General Idea

1. Generate a compilation database compile_commands.json for your project.

2. Feed the source file and the compilation database into ccmock to create mocks for your unit test code.

   ccmock --compile-commands=compile_commands.json -o <output> <input>

3. Use the preprocessor to include the generated output file in your unit test source file.

4. Focus on writing unit test code.

Commands

Help Message

ccmock

ccmock --help

ccmock -h

Write Mock Function to Standard Output

ccmock <input-file>

Write Mock Function to File

ccmock -o <output-file> <input-file>

Using Compile Flags

ccmock --compile-commands=compile_flags.txt <input-file>

Using a Compilation Database

ccmock --compile-commands=compile_commands.json <input-file>

Specifying Configuration Files

ccmock --config=<config>.yaml

ccmock --config=<config>.yaml,<config>.yaml <input-file>

CCMOCK_CONFIG=<config>.yaml ccmock --config=<config>.yaml,<config>.yaml <input-file>

Dump Effective Configuration Settings

ccmock --dump-config

ccmock --dump-config -o <output-file>

ccmock --config=<config>.yaml,<config>.yaml --blacklist=<name> --dump-config

Pass Additional Compiler Flags to the Clang Frontend

ccmock --extra-args=-DNDEBUG,-Wall,-Werror <input-file>

Best Practices

• Always name your parameters in function declarations.
• Don't mock very fundamental functions like malloc(), open(), etc... as doing so will very likey break your unit test library in unpredictable ways.

Examples

Explore the test/system directory to see how ccmock can be integrated into a build system for automatic mock generation.

Implementation Details

• C++ * Mock function calls are not associated to any specific object instance. * The constructors and destructors of global objects cannot be checked with

  mock calls.

  • Global objects can only be automatically instantiated if they have a default constructor.

Open Points

• Mocking C++ is not implemented
• Fake Function Framework generator not implemented
• Generate global variable definitions
• Restructure test tree
• Automatic include handling
• Provide multiple test runners (gtest, unity?, ctest?)
• Add support for another mock library (cpputest?)
• Implement own mocking functionality
• --backend None to just print prototypes