examples/components/echo/README.md

# Echo Example

This directory contains a simple example using program arguments and environment
variables in [Component Framework](/docs/concepts/components/introduction.md).

## Building

If these components are not present in your build, they can be added by
appending `--with //examples` to your `fx set` command. For example:

```bash
$ fx set core.x64 --with //examples --with //examples:tests
$ fx build
```

## Running

Use `ffx component run` to launch this component into a restricted realm
for development purposes:

-  **C++**

    ```bash
    $ ffx component run /core/ffx-laboratory:echo_cpp fuchsia-pkg://fuchsia.com/echo-example#meta/echo_cpp.cm
    ```

-  **Rust**

    ```bash
    $ ffx component run /core/ffx-laboratory:echo_rust fuchsia-pkg://fuchsia.com/echo-example#meta/echo_rust.cm
    ```

When the above command is run, you can see the following output with `fx log`:

```
[echo] INFO: Hello, Alice, Bob, Spot!
```

## Testing

Unit tests for echo are available in the `echo-unittests` package.
Use the `ffx test run` command to run the tests on a target device:

-  **C++**

    ```bash
    $ ffx test run fuchsia-pkg://fuchsia.com/echo-cpp-unittests#meta/echo-cpp-unittests.cm
    ```

    You should see each of the unit tests execute and pass:

    ```
    [RUNNING]       EchoTest.TestGreetOne
    [PASSED]        EchoTest.TestGreetOne
    [RUNNING]       EchoTest.TestGreetTwo
    [PASSED]        EchoTest.TestGreetTwo
    [RUNNING]       EchoTest.TestGreetThree
    [PASSED]        EchoTest.TestGreetThree

    3 out of 3 tests passed...
    fuchsia-pkg://fuchsia.com/echo-cpp-unittests#meta/echo-cpp-unittests.cm completed with result: PASSED
    ```

-  **Rust**

    ```bash
    $ ffx test run fuchsia-pkg://fuchsia.com/echo-rust-unittests#meta/echo-rust-unittests.cm
    ```

    You should see each of the unit tests execute and pass:

    ```
    Running test 'fuchsia-pkg://fuchsia.com/echo-rust-unittests#meta/echo-rust-unittests.cm'
    [RUNNING]	tests::test_greet_one
    [RUNNING]	tests::test_greet_two
    [RUNNING]	tests::test_greet_three
    [PASSED]	tests::test_greet_one
    [PASSED]	tests::test_greet_two
    [PASSED]	tests::test_greet_three

    3 out of 3 tests passed...
    ```