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Test and debug


Use the mbed test command to compile and run tests.

The testing framework is Greentea, which provides tests designed for driver porting and target verification.

The arguments to test are:

  • -m <MCU>: to select a target for the compilation. If the detect or auto parameter is passed, then Mbed CLI will attempt to detect the connected target and compile against it.
  • -t <TOOLCHAIN>: to select a toolchain from those defined in mbed_settings.py, where toolchain can either be ARM (Arm Compiler 6) or GCC_ARM (GNU Arm Embedded).
  • --compile-list: to list all the tests that can be built.
  • --run-list: to list all the tests that can be run, after they have been built.
  • --compile: to only compile the tests.
  • --run: to only run the tests.
  • -n <TESTS_BY_NAME>: to limit the tests built or run to a comma separated list, for example, test1, test2, test3.
  • --source <SOURCE>: to select the source directory. The default is . for the the current directory. You can specify multiple source locations, even outside the program tree. Find more details about the --source switch in the build rules documentation.
  • --build <BUILD>: to select the build directory. The default is BUILD/ inside your program.
  • --profile <PATH_TO_BUILD_PROFILE>: to select a path to a build profile configuration file, for example, mbed-os/tools/profiles/debug.json. See the dedicated build profile documentation for more detail.
  • -c or --clean: to clean the build directory before compiling.
  • --test-spec <TEST_SPEC>: to set the path for the test specification file used when building and running tests. The default path is the build directory.
  • --build-data <BUILD_DATA>: dumps build_data to this file.
  • --app-config <APP_CONFIG>: the path of an app configuration file. The default is to look for mbed_app.json.
  • --test-config <TEST_CONFIG>: the path or Mbed OS keyword of a test configuration file, for example, ethernet, odin_wifi or path/to/config.json.
  • --greentea: to run Greentea tests. As a default, it only runs Greentea tests.
  • -v or --verbose: for verbose diagnostic output.
  • -vv or --very_verbose: for very verbose diagnostic output.

To invoke the mbed test:

$ mbed test -m K64F -t GCC_ARM
Building library mbed-build (K64F, GCC_ARM)
Building project GCC_ARM to TESTS-unit-myclass (K64F, GCC_ARM)
Compile: main.cpp
Link: TESTS-unit-myclass
Elf2Bin: TESTS-unit-myclass
| Module    | .text | .data | .bss |
| Fill      |   74  |   0   | 2092 |
| Misc      | 47039 |  204  | 4272 |
| Subtotals | 47113 |  204  | 6364 |
Allocated Heap: 65540 bytes
Allocated Stack: 32768 bytes
Total Static RAM memory (data + bss): 6568 bytes
Total RAM memory (data + bss + heap + stack): 104876 bytes
Total Flash memory (text + data + misc): 48357 bytes
Image: BUILD/tests/K64F/GCC_ARM/rtos/tests/TESTS/mbed_rtos/mutex/TESTS-unit-myclass.bin
mbedgt: test suite report:
| target       | platform_name | test suite                      | result | elapsed_time (sec) | copy_method |
| K64F-GCC_ARM | K64F          | TESTS-unit-myclass              | OK     | 21.09              |    shell    |
mbedgt: test suite results: 1 OK
mbedgt: test case report:
| target       | platform_name | test suite         | test case           | passed | failed | result | elapsed_time (sec) |
| K64F-GCC_ARM | K64F          | TESTS-unit-myclass | TESTS-unit-myclass1 | 1      | 0      | OK     | 5.00               |
| K64F-GCC_ARM | K64F          | TESTS-unit-myclass | TESTS-unit-myclass2 | 1      | 0      | OK     | 5.00               |
| K64F-GCC_ARM | K64F          | TESTS-unit-myclass | TESTS-unit-myclass3 | 1      | 0      | OK     | 5.00               |
mbedgt: test case results: 3 OK
mbedgt: completed in 21.28 sec

You can find the compiled binaries and test artifacts in the BUILD/tests/<TARGET>/<TOOLCHAIN> directory of your program.

Finding available tests

You can find the tests that are available for building by using the --compile-list option:

$ mbed test --compile-list
Test Case:
    Name: TESTS-functional-test1
    Path: .\TESTS\functional\test1
Test Case:
    Name: TESTS-functional-test2
    Path: .\TESTS\functional\test2
Test Case:
    Name: TESTS-functional-test3
    Path: .\TESTS\functional\test3

You can find the tests that are available for running by using the --run-list option:

$ mbed test --run-list
mbedgt: test specification file '.\build\tests\K64F\ARM\test_spec.json' (specified with --test-spec option)
mbedgt: using '.\build\tests\K64F\ARM\test_spec.json' from current directory!
mbedgt: available tests for built 'K64F-ARM', location '.\build\tests\K64F\ARM'
        test 'TESTS-functional-test1'
        test 'TESTS-functional-test2'
        test 'TESTS-functional-test3'

Compiling and running tests

You can specify that the tests only build by using the --compile option:

$ mbed test -m K64F -t GCC_ARM --compile

You can specify that the tests only run by using the --run option:

$ mbed test -m K64F -t GCC_ARM --run

If you don't specify any of these, mbed test first compiles all available tests and then runs them.

Limiting the test scope

You can limit the scope of the tests built and run by using the -n option. This takes a comma-separated list of test names as an argument:

$ mbed test -m K64F -t GCC_ARM -n TESTS-functional-test1,TESTS-functional-test2

You can use the wildcard character * to run a group of tests that share a common prefix without specifying each test individually. For instance, if you only want to run the three tests, TESTS-functional-test1, TESTS-functional-test2 and TESTS-functional-test3, but you have other tests in your project, you can run:

$ mbed test -m NUCLEO_F429ZI -t GCC_ARM -n TESTS-functional*

Note: Some shells expand the wildcard character * into file names that exist in your working directory. To prevent this behavior, please see your shell's documentation.

Test directory structure

Test code must follow this directory structure:

 |- main.cpp            ## Optional main.cpp with main() if it is an application module.
 |- pqr.lib             ## Required libs
 |- xyz.lib
 |- mbed-os
 |  |- frameworks        ## Test dependencies
 |  |  `_greentea-client ## Greentea client required by tests.
 |  |...
 |  `- TESTS              ## Tests directory. Special name upper case TESTS is excluded during application build process
 |     |- TestGroup1      ## Test Group directory
 |     |  `- TestCase1    ## Test case source directory
 |     |      `- main.cpp ## Test source
 |     |- TestGroup2
 |     |   `- TestCase2
 |     |      `- main.cpp
 |     `- host_tests      ## Python host tests script directory
 |        |- host_test1.py
 |        `- host_test2.py
 `- build                 ## Build directory
     |- <TARGET>          ## Target directory
     | `- <TOOLCHAIN>     ## Toolchain directory
     |   |- TestCase1.bin ## Test binary
     |   `- TestCase2.bin
     | ....

As shown above, tests exist inside TESTS\testgroup\testcase\ directories. Please note that TESTS is a special upper-case directory that is excluded from module sources while compiling.

Note: mbed test does not work in applications that contain a main function that is outside of a TESTS directory.

Unit testing

Use the mbed test --unittests command to build and run unit tests, or to generate files for new unit tests.

Build and run unit tests with mbed test --unittests. 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 test --unittests --new <FILE>.

Building and running unit tests

You can specify to only build the unit tests by using the --compile option:

$ mbed test --unittests --compile

You can specify to only run the unit tests by using the --run option:

$ mbed test --unittests --run

If you do not specify any of these, mbed test --unittests builds all available unit tests and runs 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 test --unittests -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 test --unittests --coverage html

Creating new unit tests

All unit tests are under the 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 test --unittests --new rtos/Semaphore.cpp

Serial terminal

You can open a serial terminal to the serial port of a connected Mbed target (usually board) using the mbed sterm command. If no serial port is specified, Mbed CLI will attempt to detect the connected Mbed targets and their serial ports.

There are various options to mbed sterm:

  • --port <serial port> to specify a system serial port to connect to.
  • --baudrate <numeric> to select the communication baudrate; the default value is 9600.
  • --echo <on|off> to switch local echo (default is on).
  • --reset to reset the connected target by sending Break before opening the serial terminal.

You can also set default port, baudrate and echo mode using the TERM_PORT, TERM_BAUDRATE and TERM_ECHO Mbed CLI configuration options.

The following shortcuts are available within the serial terminal:

  • Ctrl+B - Send Break (reset target)
  • Ctrl+C - Exit terminal
  • Ctrl+E - Toggle local echo
  • Ctrl+H - Help
  • Ctrl+T - Menu escape key

You can view more shortcuts in the serial terminal's help menu (Ctrl+H).

You can also add the --sterm option to mbed compile -f to compile a new program, flash the program/firmware image to the connected target and then open the serial terminal to its serial port:

$ mbed compile -t GCC_ARM -m K64F -f --sterm


Import Mercurial (mbed.org) programs or libraries

  1. Check whether you have Mercurial installed in your system path by running hg in the command prompt. If you are receiving "command not found" or a similar message, then you need to install Mercurial and add it to your system path.
  2. Try to clone a Mercurial repository directly. For example, hg clone https://developer.mbed.org/teams/mbed/code/mbed_blinky/. If you receive an error similar to abort: error: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.:590), then your system certificates are out of date. You need to update your system certificates and possibly add the host certificate fingerprint of mbed.com and mbed.org. You can read more about Mercurial's certificate management.

Various issues when running Mbed CLI in the Cygwin environment

Mbed CLI is not currently compatible with the Cygwin environment and cannot be executed inside it.

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