Unit tests: improve unit testing documentation

UNITTESTS/README.md

@@ -1,6 +1,6 @@
 ## Unit testing
 
-This document describes how to write and test unit tests for Mbed OS. To prevent and solve problems, please see the [troubleshooting](#troubleshooting) section.
+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.
 
 ### Introduction
 
@@ -16,7 +16,7 @@ Please install the following dependencies to use Mbed OS unit testing.
 - Python 2.7.x, 3.5 or newer.
 - Pip 10.0 or newer.
 - Gcovr 4.1 or newer.
-- Mbed CLI 1.8.0 or newer.
+- Arm Mbed CLI 1.8.0 or newer.
 
 Detailed instructions for supported operating systems are below.
 
@@ -30,7 +30,7 @@ Detailed instructions for supported operating systems are below.
    sudo easy_install pip
    ```
 
-1. Install Gcovr and [Mbed CLI](https://os.mbed.com/docs/latest/tools/arm-mbed-cli.html) with `pip install "gcovr>=4.1" mbed-cli`.
+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`.
 
 #### Installing dependencies on macOS
 
@@ -43,15 +43,15 @@ Detailed instructions for supported operating systems are below.
    sudo easy_install pip
    ```
 
-1. Install Gcovr and [Mbed CLI](https://os.mbed.com/docs/latest/tools/arm-mbed-cli.html) with `pip install "gcovr>=4.1" mbed-cli`.
+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`.
 
 #### Installing dependencies on Windows
 
 1. Download and install [MinGW-W64](http://mingw-w64.org/).
 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/arm-mbed-cli.html) with `pip install "gcovr>=4.1" mbed-cli`.
+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
 
@@ -69,7 +69,7 @@ The build system automatically generates names of test suites. The name is const
 
 ### 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 in handbook](https://os.mbed.com/docs/latest/tools/arm-mbed-cli.html).
+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).
 
 ### Writing unit tests
 
@@ -154,17 +154,19 @@ TEST_F(TestSemaphore, constructor)
 
 ### Building and running unit tests
 
-Use Mbed CLI to build and run unit tests. For advanced use, you can run CMake and a make program directly.
+Use Mbed CLI to build and run unit tests. For advanced use, you can run CMake and a Make program directly.
 
 #### Build tests directly with CMake
 
 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 `-DCOVERAGE:True` to add coverage compiler flags.
+   - 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 (Make, Gmake, Mingw32-make and so on) to build the tests.
+1. Run a Make program to build the tests.
 
 #### Run tests directly with CTest
 
@@ -177,14 +179,24 @@ Run a test binary in the build directory to run a unit test suite. To run multip
 1. Add test executables into the list.
 1. Run them.
 
+### 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.
+
 ### Get code coverage
 
-Use Mbed CLI to generate code coverage reports. For advanced use, you can run Gcovr or any other code coverage tool directly in the build directory.
+Use Mbed CLI to generate code coverage reports. For advanced use, follow these steps:
+
+1. Run CMake with both `-DCMAKE_BUILD_TYPE=Debug` and `-DCOVERAGE=True`.
+1. Run a Make program to build the tests.
+1. Run the tests.
+1. Run Gcovr or any other code coverage tool directly in the build directory.
 
 ### Troubleshooting
 
 **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.
+* **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.