Merge pull request #8819 from lorjala/unittests-docs

Improve the unit testing documentation

Author: Cruz Monrreal

UNITTESTS/README.md

@@ -1,27 +1,29 @@
 ## Unit testing
 
-This document describes how to write and test unit tests for Arm Mbed OS. To prevent and solve problems, please see the [troubleshooting](#troubleshooting) section.
+This document describes how to write and use unit tests for Arm Mbed OS. 
 
 ### Introduction
 
-Unit tests test code in small sections on a host machine. Unlike other testing tools, unit testing doesn't require embedded hardware, and it doesn't need to build the full operating system. Because of this, unit testing can result in faster tests than other testing tools. Unit testing takes place in a build environment where we test each C or C++ class or module in isolation. This means we build test suites into separate test binaries and stub all access outside to remove dependencies on any specific embedded hardware or software combination. This allows us to complete the testing using native compilers on the build machine.
+Unit tests test code in small sections on a host machine. Unlike other testing tools, unit testing doesn't require embedded hardware or need to build a full operating system. Because of this, unit testing can result in faster tests than other tools. Unit testing happens in a build environment where you test each C or C++ class or module in isolation. Build test suites into separate test binaries and stub all access outside to remove dependencies on any specific embedded hardware or software combination. This allows you to complete tests using native compilers on the build machine.
 
 ### Prerequisites
 
-Please install the following dependencies to use Mbed OS unit testing. 
+Please install the following dependencies to use Mbed OS unit testing:
 
-- GNU toolchains.
-   - GCC 6 or later. We recommend you use MinGW-W64 on Windows, but any Windows port of the above GCC versions works. Default compilers can be used on Mac OS instead of GCC to shorten build times, but code coverage results can then differ.
-- CMake 3.0 or newer.
-- Python 2.7.x, 3.5 or newer.
-- Pip 10.0 or newer.
-- Gcovr 4.1 or newer.
-- Arm Mbed CLI 1.8.0 or newer.
+* GNU toolchains.
+   * GCC 6 or later. We recommend you use MinGW-W64 on Windows, but any Windows port of the above GCC versions works. Default compilers can be used on Mac OS instead of GCC to shorten build times, but code coverage results can differ.
+* CMake 3.0 or newer.
+* Python 2.7.x, 3.5 or newer.
+* Pip 10.0 or newer.
+* Gcovr 4.1 or newer.
+* Arm Mbed CLI 1.8.0 or newer.
 
 Detailed instructions for supported operating systems are below.
 
 #### Installing dependencies on Debian or Ubuntu
 
+In a terminal window:
+
 1. `sudo apt-get -y install build-essential cmake`
 1. Install Python and Pip with:
 
@@ -34,6 +36,8 @@ Detailed instructions for supported operating systems are below.
 
 #### Installing dependencies on macOS
 
+In a terminal window:
+
 1. Install [Homebrew](https://brew.sh/).
 1. Install Xcode Command Line Tools with `xcode-select --install`.
 1. Install CMake with: `brew install cmake`.
@@ -49,42 +53,56 @@ Detailed instructions for supported operating systems are below.
 
 #### Installing dependencies on Windows
 
-1. Download and install [MinGW-W64](http://mingw-w64.org/).
+In a terminal window:
+
+1. Download and install MinGW-W64 from [SourceForge](https://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win64/Personal%20Builds/mingw-builds/).
 1. Download CMake binaries from https://cmake.org/download/, and run the installer.
 1. Download Python 2.7 or Python 3 from https://www.python.org/getit/, and run the installer.
 1. Add MinGW, CMake and Python into system PATH.
 1. Install Gcovr and [Mbed CLI](https://os.mbed.com/docs/latest/tools/developing-arm-mbed-cli.html) with `pip install "gcovr>=4.1" mbed-cli`.
 
 ### Test code structure
 
-Unit tests are located in the Mbed OS repository under the `UNITTESTS` folder. We recommend unit test files use an identical directory path to the file under test. This makes it easier to find unit tests for a particular class or a module. For example, if the file under test is `some/example/path/ClassName.cpp`, then all the test files are in the `UNITTESTS/some/example/path/ClassName` directory. Each test suite needs to have its own `unittest.cmake` file for test configuration.
+Find unit tests in the Mbed OS repository under the `UNITTESTS` folder. We recommend unit test files use an identical directory path as the file under test. This makes it easier to find unit tests for a particular class or a module. For example, if the file you're testing is `some/example/path/ClassName.cpp`, then all the test files are in the `UNITTESTS/some/example/path/ClassName` directory. Each test suite needs to have its own `unittest.cmake` file for test configuration.
+
+All the class stubs should be located in the `UNITTESTS/stubs` directory. A single stub class can be used by multiple test suites and should follow the naming convention `ClassName_stub.cpp` for the source file, and `ClassName_stub.h` for the header file. Use the actual header files for the unit tests, and don't stub headers if possible. The stubbed headers reside in the `UNITTESTS/target_h` directory.
 
 #### Test discovery
 
-Registering unit tests for running is automatic, and the test runner handles registration. However, test files are not automatically assigned to be built. We build unit tests by using a separate build system, which searches for unit tests under the `UNITTESTS` directory.
+Registering unit tests to run happens automatically, and the test runner handles registration. However, test files do not automatically  build. Build unit tests with a separate system that searches for unit tests under the `UNITTESTS` directory.
 
-For the build system to find and build any test suite automatically, you must include a unit test configuration file named `unittest.cmake` for each unit test suite. This configuration file contains all the source files required for the build.
+For the build system to find and build any test suite automatically, include a unit test configuration file named `unittest.cmake` for each unit test suite. This configuration file lists all the source files required for the test build.
 
 #### Test names
 
 The build system automatically generates names of test suites. The name is constructed by taking a relative file path from the UNITTESTS directory to the test directory and replacing path separators with dashes. For example, the test suite name for `some/example/path/ClassName.cpp` is `some-example-path-ClassName`. Suite names are used when deciding which test suites to run.
 
 ### Unit testing with Mbed CLI
 
-Mbed CLI supports unit tests through `mbed test --unittests` command. For information on using Mbed CLI, please see the [CLI documentation](https://os.mbed.com/docs/latest/tools/developing-arm-mbed-cli.html).
+Mbed CLI supports unit tests through the `mbed test --unittests` command. For information on using Mbed CLI, please see the [CLI documentation](https://os.mbed.com/docs/latest/tools/developing-arm-mbed-cli.html).
 
 ### Writing unit tests
 
+A unit tests suite consists of one or more test cases. The test cases should cover all the functions in a class under test. All the external dependencies are stubbed including the other classes in the same module. Avoid stubbing header files. Finally, analyze code coverage to ensure all code is tested, and no dead code is found.
+
+Please see the [documentation for Google Test](https://github.com/google/googletest/blob/master/googletest/docs/primer.md) to learn how to write unit tests using its framework. See the [documentation for Google Mock](https://github.com/google/googletest/blob/master/googlemock/docs/Documentation.md) if you want to write and use C++ mock classes instead of stubs.
+
+#### Test suite configuration
+
 Create two files in the test directory for each test suite:
 
-- Unit test source file (`test_ClassName.cpp`).
-- Unit test configuration file (`unittest.cmake`).
+* Unit test source file (`test_ClassName.cpp`).
+* Unit test configuration file (`unittest.cmake`).
+
+List all the required files for the build in the `unittest.cmake` file with paths relative to the `UNITTESTS` folder. Use the following variables to list the source files and include paths:
+
+* **unittest-includes**: List of header include paths. You can use this to extend or overwrite default paths listed in `UNITTESTS/CMakeLists.txt`.
+* **unittest-sources**: List of files under test.
+* **unittest-test-sources**: List of test sources and stubs.
 
-List all the files required for the build in the `unittest.cmake` file. We recommend you list the file paths relative to the `UNITTESTS` folder. Use the following variables to list the source files and include paths:
+You can also set custom compiler flags and other configurations supported by CMake in `unittest.cmake`.
 
-- **unittest-includes** - List of header include paths. You can use this to extend or overwrite default paths listed in CMakeLists.txt.
-- **unittest-sources** - List of files under test.
-- **unittest-test-sources** - List of test sources and stubs.
+#### Example
 
 With the following steps, you can write a simple unit test. In this example, `rtos/Semaphore.cpp` is a class under test.
 
@@ -97,11 +115,13 @@ With the following steps, you can write a simple unit test. In this example, `rt
    )
    
    set(unittest-test-sources
-       stubs/mbed_assert.c
+       stubs/mbed_assert_stub.c
+       stubs/Kernel_stub.cpp
        rtos/Semaphore/test_Semaphore.cpp
    )
    ```
-
+1. Stub all external dependencies. Create stubs `UNITTESTS/stubs/mbed_assert_stub.c` and `UNITTESTS/stubs/Kernel_stub.cpp` if they don't already exist.
+1. Update header stubs with any missing type or function declarations.
 1. Create a test source file `UNITTESTS/rtos/Semaphore/test_Semaphore.cpp` with the following content:
 
 ```
@@ -163,28 +183,28 @@ Use Mbed CLI to build and run unit tests. For advanced use, you can run CMake an
 1. Create a build directory `mkdir UNITTESTS/build`.
 1. Move to the build directory `cd UNITTESTS/build`.
 1. Run CMake using a relative path to `UNITTESTS` folder as the argument. So from `UNITTESTS/build` use `cmake ..`:
-   - Add `-g [generator]` if generating other than Unix Makefiles such in case of MinGW use `-g "MinGW Makefiles"`.
-   - Add `-DCMAKE_MAKE_PROGRAM=<value>`, `-DCMAKE_CXX_COMPILER=<value>` and `-DCMAKE_C_COMPILER=<value>` to use a specific Make program and compilers.
-   - Add `-DCMAKE_BUILD_TYPE=Debug` to build a debug build.
-   - Add `-DCOVERAGE=True` to add coverage compiler flags.
-   - See the [CMake manual](https://cmake.org/cmake/help/v3.0/manual/cmake.1.html) for more information.
-1. Run a Make program to build the tests.
+   * Add `-g [generator]` if generating other than Unix Makefiles such in case of MinGW use `-g "MinGW Makefiles"`.
+   * Add `-DCMAKE_MAKE_PROGRAM=<value>`, `-DCMAKE_CXX_COMPILER=<value>` and `-DCMAKE_C_COMPILER=<value>` to use a specific Make program and compilers.
+   * Add `-DCMAKE_BUILD_TYPE=Debug` for a debug build.
+   * Add `-DCOVERAGE=True` to add coverage compiler flags.
+   * See the [CMake manual](https://cmake.org/cmake/help/v3.0/manual/cmake.1.html) for more information.
+1. Run a Make program to build tests.
 
 #### Run tests directly with CTest
 
-Run a test binary in the build directory to run a unit test suite. To run multiple test suites at once, use CTest test runner. Run CTest with `ctest`. Add `-v` to get results for each test case. See the [CTest manual](https://cmake.org/cmake/help/v3.0/manual/ctest.1.html) for more information.
+Run a test binary in the build directory to run a unit test suite. To run multiple test suites at once, use the CTest test runner. Run CTest with `ctest`. Add `-v` to get results for each test case. See the [CTest manual](https://cmake.org/cmake/help/v3.0/manual/ctest.1.html) for more information.
 
 #### Run tests with GUI test runner
 
-1. Install *gtest-runner* using the [documentation](https://github.com/nholthaus/gtest-runner).
-1. Run *gtest-runner*
-1. Add test executables into the list.
-1. Run them.
+1. Install `gtest-runner` according to the [documentation](https://github.com/nholthaus/gtest-runner).
+1. Run `gtest-runner`.
+1. Add test executables into the list and run.
 
 ### Debugging
 
 1. Use Mbed CLI to build a debug build. For advanced use, run CMake directly with `-DCMAKE_BUILD_TYPE=Debug`, and then run a Make program.
 1. Run GDB with a test executable as an argument to debug unit tests.
+1. Run tests with Valgrind to analyze the test memory profile.
 
 ### Get code coverage
 
@@ -200,8 +220,11 @@ Use Mbed CLI to generate code coverage reports. For advanced use, follow these s
 **Problem:** Generic problems with CMake or with the build process.
 * **Solution**: Delete the build directory. Make sure that CMake, g++, GCC and a Make program can be found in the path and are correct versions.
 
-**Problem:** Virus protection identifies files generated by CMake as malicious and quarantines the files on Windows.
-* **Solution**: Restore the false positive files from the quarantine.
+**Problem:** (Windows) Virus protection identifies files generated by CMake as malicious and quarantines the files.
+* **Solution**: Restore false-positive files from the quarantine.
+
+**Problem:** (Windows) Git with shell installation adds sh.exe to the path and then CMake throws an error: sh.exe was found in your PATH. For MinGW make to work correctly, sh.exe must NOT be in your path.
+* **Solution**:  Remove sh.exe from the system path.
 
-**Problem:** CMake compiler check fails on Mac OS Mojave when using GCC-8.
+**Problem:** (Mac OS) CMake compiler check fails on Mac OS Mojave when using GCC-8.
 * **Solution**: Make sure gnm (binutils) is not installed. Uninstall binutils with `brew uninstall binutils`.