esphome/tests/components/README.md

How to write C++ ESPHome unit tests

1. Locate the folder with your component or create a new one with the same name as the component.
2. Write the tests. You can add as many .cpp and .h files as you need to organize your tests.

IMPORTANT: wrap all your testing code in a unique namespace to avoid linker collisions when compiling testing binaries that combine many components. By convention, this unique namespace is esphome::component::testing (where "component" is the component under test), for example: esphome::uart::testing.

Running component unit tests

(from the repository root)

./script/cpp_unit_test.py component1 component2 ...

The above will compile and run the provided components and their tests.

To run all tests, you can invoke cpp_unit_test.py with the special --all flag:

./script/cpp_unit_test.py --all

To run a specific test suite, you can provide a Google Test filter:

GTEST_FILTER='UART*' ./script/cpp_unit_test.py uart modbus

The process will return 0 for success or nonzero for failure. In case of failure, the errors will be printed out to the console.