move unit testing documentation for mbed cli to cli-test-debug.md

Author: lorjala

docs/tools/offline/cli-test-debug.md

@@ -1,5 +1,7 @@
 ## Test and debug
 
+### Testing
+
 Use the `mbed test` command to compile and run tests.
 
 The arguments to `test` are:
@@ -158,6 +160,65 @@ As shown above, tests exist inside `TESTS\testgroup\testcase\` directories. Plea
 
 <span class="notes">**Note:** `mbed test` does not work in applications that contain a  `main` function that is outside of a `TESTS` directory.</span>
 
+### Unit testing
+
+Use the `mbed unittest` command to build and run unit tests, or to generate files for new unit tests.
+
+Build and run unit tests with `mbed unittest`. The arguments are:
+
+* `--compile` to only compile unit tests.
+* `--run` to only run unit tests.
+* `-c` or `--clean` to clean build directory.
+* `-d` or `--debug` to prepare debug build.
+* `--coverage <TYPE>` to generate code coverage report where TYPE can be "html", "xml" or "both".
+* `-m <NAME>` or `--make-program <NAME>` to select which make build tool to use where NAME can be "make", "gmake", "mingw32-make" or "ninja".
+* `-g <NAME>` or `--generator <NAME>` to select which CMake generator to use where NAME can be "Unix Makefiles", "MinGW Makefiles" or "Ninja".
+* `-r <EXPRESSION>` or `--regex <EXPRESSION>` to run tests matching the regular expression.
+* `--build <PATH>` to specify build directory.
+* `-v` or `--verbose` for verbose diagnostic output.
+
+Generate files for a new unit test with `mbed unittest --new <FILE>`.
+
+### Building and running unit tests
+
+You can specify to only **build** the unit tests by using the `--compile option:
+
+```
+$ mbed unittest --compile
+```
+
+You can specify to only **run** the unit tests by using the `--run` option:
+
+```
+$ mbed unittest --run
+```
+
+If you do not specify any of these, `mbed unittest` will build all available unit tests and run them.
+
+### Running a subset of tests
+
+You can run a **limited set** of unit tests by using the `-r` or `--regex` option. This takes a regular expression, which it compares against the test names. For example to run all cellular unit tests you can specify:
+
+```
+$ mbed unittest -r cellular
+```
+
+### Getting code coverage
+
+You can generate a code coverage report by using the `--coverage` option. For example to create an html report you can specify:
+
+```
+$ mbed unittest --coverage html
+```
+
+### Creating new unit tests
+
+All unit tests are under `mbed-os/UNITTESTS` directory. You can **generate** the necessary files for a unit test by using the `--new` option. For example to create the files for `rtos/Semaphore.cpp` you can specify:
+
+```
+$ mbed unittest --new rtos/Semaphore.cpp
+```
+
 ### Troubleshooting
 
 #### Unable to import Mercurial (mbed.org) programs or libraries.