docs/development/testing/cts/contributing_tests.md - fuchsia - Git at Google

 # Contributing Tests to CTS

 This guide provides instructions on how to contribute a test to CTS.

 ## How to write an ABI test

 An ABI test is a test that verifies the ABI or runtime behavior of an API in
 the SDK. These tests are distributed as Fuchsia packages containing test
 components and run entirely on the target device.

 ### Prerequisites

 * Your test must be written in C, C++, or Rust.
 * This guide assumes the reader is familiar with Fuchsia [Packages],
 [Components] and [Component Manifests].


 ### Step 1: Create a test directory

 The structure of the `//sdk/cts` directory mirrors the structure of SDK
 artifacts. Your test should go in the same directory as the interface under test
 is found in an SDK. For example:

 | Tests for... | Should go in... |
 |--------------|-----------------|
 | Host tools   | //sdk/cts/tests/tools |
 | FIDL interfaces | //sdk/cts/tests/fidl |
 | Libraries    | //sdk/cts/tests/pkg |

 See existing tests under `//sdk/cts/tests` for examples.

 ### Step 2: Create your test executable

 Note: The CTS build templates verify that dependencies are released in an SDK.
 If your test needs an exception, [file a bug] in `DeveloperExperience>CTS`. The
 allow list can be found [here](/sdk/cts/build/allowed_cts_deps.gni).

 In your test directory's `BUILD.gn` file, create a test executable using CTS
 build templates.

   * {C/C++}

     ```gn
     import("//sdk/cts/build/cts.gni")

     cts_executable("my_test_binary") {
       deps = [ "//zircon/system/ulib/zxtest" ]
       sources = [ "my_test.cc" ]
       testonly = true
     }
     ```

   * {Rust}

   ```gn
   import("//sdk/cts/build/cts.gni")

   cts_rustc_test("my_test_binary") {
     edition = "2018"
     source_root = "src/my_test.rs"
     sources = [ "src/my_test.rs" ]
   }
   ```

 ### Step 3: Create your test component

 Note: This section assumes familiarity with the concept of [Test Components].

 ```json5
 // my_test_component.cml
 {
     include: [
         // Select the appropriate test runner shard here:
         // rust, elf, etc.
         "//src/sys/test_runners/rust/default.shard.cml",
     ],
     program: {
         binary: "bin/my_test_binary",
     },
     facets: {
         // mark your test type "cts".
         "fuchsia.test": { type: "cts" },
     },
     ...
 }
 ```

 Wrap your executable as a Fuchsia component. CTS provides a special GN template
 for creating a component:

 ```gn
 cts_fuchsia_component("my_test_component") {
   testonly = true
   manifest = "meta/my_test_component.cml",
   deps = [ ":my_test_binary" ]
 }
 ```

 ### Step 4: Create your test package

 CTS also provides a special GN template for creating a test package:

 ```gn
 cts_fuchsia_test_package("my_test") {
   package_name = "my_test"
   test_components = [ ":my_test_component" ]
 }
 ```

 ### Step 5: Run the test

 These instructions require you to open several terminal tabs.

 #### Tab 1: Start the Fuchsia package server

 ```
 fx serve
 ```

 #### Tab 2: Start the Fuchsia emulator

 ```
 ffx emu start --headless
 ```

 * `--headless` disables graphical output.

 For more information on configuring the emulator, see [Start the Fuchsia Emulator].

 #### Tab 3: Stream the device logs

 This step is useful for debugging your test.

 ```
 ffx log
 ```

 #### Tab 4: Run the test

 <pre class="prettyprint">
 <code class="devsite-terminal">fx set core.x64 --with <var>TARGET_LABEL</var> </code>
 <code class="devsite-terminal">fx test <var>TARGET_LABEL</var> # or fx test <var>TEST_NAME</var> </code>
 </pre>

 * `-v` enables verbose output.

 See the section about "Debugging tips" below.

 ### Step 6. Verify your test passes as part of the CTS release

 This step involves building the CTS in the same way that our CI does when it is
 released, then running those CTS tests in your local checkout. It is necessary
 because upon release, we automatically rewrite each CTS test package's name to
 deduplicate it from the same package's name at HEAD (the build does not allow
 duplicate names) and we must verify that the test still passes after this
 rewrite.

 Follow the instructions in Step 4 to start an emulator and a package server,
 then launch a new terminal and run the following command:

 ```
 $FUCHSIA_DIR/sdk/cts/build/scripts/verify_release/verify_release.py
 ```

 This command will build the CTS archive, release it to your
 `//prebuilt/cts/test/*` directory, and run the tests contained therein. After
 a brief pause, the test results will be printed to the terminal window.

 To learn more about that script, or to run the commands manually, please see
 [//sdk/cts/build/scripts/verify_release/README.md](https://fuchsia.googlesource.com/fuchsia/+/refs/heads/main/sdk/cts/build/scripts/verify_release/README.md).

 Some common causes of test failure at this stage include:

 * The test launches one of its child components using an absolute component URL.
   * **Explanation**: The URL is no longer correct because the test's package was
   renamed.
   * **Solution**: Use a [relative component URL] instead.
 * The test is missing a dependency.
   * **Explanation**: It's possible that the Fuchsia system contained a different
   set of packages when you built and ran your test at HEAD vs as part of the CTS
   and that your test depended on some of those packages.
   * **Solution**: Make sure your test's GN target explicitly lists all of its
   direct dependencies as `deps`.

 If you need additional help debugging at this step, please reach out to the CTS
 team by filing a bug in the [CTS bug component].

 ### Step 7. Make the test run on presubmit

 This step causes the version of your test from Fuchsia's HEAD commit to run as
 part of Fuchsia's presumbit queue. It *does not* include your test in the CTS
 release (See the next section).

 Add a "tests" group to your BUILD file:

 ```
 group("tests") {
   testonly = true
   deps = [ ":my_test" ]
 }
 ```

 Next add this target as a dependency to the closest ancestor `group("tests")`
 target.

 ### Step 8. Make the test run as part of the CTS release

 This step includes your test in the CTS release, which guarantees that your test
 cannot be broken between Fuchsia milestone releases (typically made every six
 weeks).

 Add an `sdk_molecule` target and use it to mark all of your test packages for
 inclusion in CTS. Each `cts_*` template declares an `sdk_atom` or `sdk_molecule`
 target with the name `${target_name}_sdk`. List each of the test packages as
 dependencies:

 ```
 sdk_molecule("test_sdks") {
   testonly = true
   deps = [ ":my_test_sdk" ]
 }
 ```

 Next add this target as a dependency to the closest ancestor
 `sdk_molecule("test_sdks")`.

 Once these steps are complete, submit your change and you should see your test run
 as part of the next CTS release.

 ### Debugging Tips

 * If your test hangs, use `ffx component list -v` to inspect its current state.

 ## How to write a test for experimental FIDL

 The CTS supports writing tests for FIDL interfaces that are not yet released in
 the SDK. This allows you to write CTS tests for your API while you are still
 developing it. Writing tests using the CTS framework while you develop your API
 ensures that your tests do not depend on any non-SDK targets.

 ### Step 1. Ensure your FIDL is marked as experimental
 Your FIDL interface should be marked with `sdk_category = "experimental"`. If
 your interface is marked as `public` or `partner`, follow the steps above to
 write a CTS test.

 ```
 fidl("fuchsia.interface") {
   sdk_category = "experimental"
   name = "fuchsia.interface"
   sources = [ "interface.fidl" ]
 }
 ```

 ### Step 2. Add your FIDL to the CTS allow list
 The CTS verifies that its dependencies are in the SDK. To avoid build time
 errors, your FIDL must be added to the CTS [allow list].

 ```
 # //sdk/cts/build/allowed_cts_deps.gni
 ALLOWED_EXPERIMENTAL_FIDL = [
   ...,
   "//absolute/path/to/experimental:fidl"
 ]
 ```

 ### Step 3. Follow the steps above to write an ABI test
 Follow the steps in the [How to write an ABI test](#how_to_write_an_abi_test)
 section to write an ABI test for your experimental FIDL.

 ### Step 4. Mark your test package as experimental
 The CTS includes tests based on metadata generated by
 `cts_fuchsia_test_package`. To avoid generating this metadata (and including
 your test in the CTS), mark your test package with `uses_experimental_fidl`.

 ```
 cts_fuchsia_test_package("my_experimental_test") {
   uses_experimental_fidl = true
   test_components = [ ":my_experimental_component" ]
 }
 ```

 ### Step 5. Release your CTS test
 When your FIDL interface is no longer experimental, release your CTS test!
 To release your CTS test, follow the steps in the
 [How to write an ABI test](#how_to_write_an_abi_test) section and delete the
 `uses_experimental_fidl` line from your `cts_fuchsia_test_package`.

 ## How to remove an ABI test

 Please see the FAQ section about [retiring tests].

 ## How to disable your test

 Please see the FAQ section about [disabling tests].

 [Component Manifests]: /docs/concepts/components/v2/component_manifests.md
 [Components]: /docs/concepts/components/v2
 [Fuchsia language policy]: /docs/contribute/governance/policy/programming_languages.md
 [Packages]: /docs/concepts/packages/package.md
 [Start the Fuchsia Emulator]: /docs/get-started/set_up_femu.md
 [Test Components]: /docs/development/testing/components/test_component.md
 [file a bug]: https://bugs.fuchsia.dev/p/fuchsia/issues/list?q=component%3ADeveloperExperience%3ECTS
 [relative component URL]: /docs/reference/components/url.md#relative
 [CTS bug component]: https://bugs.fuchsia.dev/p/fuchsia/templates/detail?saved=1&template=Fuchsia%20Compatibility%20Test%20Suite%20%28CTS%29&ts=1627669234
 [disabling tests]: /docs/development/testing/cts/faq.md#disable-a-test
 [retiring tests]: /docs/development/testing/cts/faq.md#retire-a-test
 [allow list]: /sdk/cts/build/allowed_cts_deps.gni
	# Contributing Tests to CTS

	This guide provides instructions on how to contribute a test to CTS.

	## How to write an ABI test

	An ABI test is a test that verifies the ABI or runtime behavior of an API in
	the SDK. These tests are distributed as Fuchsia packages containing test
	components and run entirely on the target device.

	### Prerequisites

	* Your test must be written in C, C++, or Rust.
	* This guide assumes the reader is familiar with Fuchsia [Packages],
	[Components] and [Component Manifests].


	### Step 1: Create a test directory

	The structure of the `//sdk/cts` directory mirrors the structure of SDK
	artifacts. Your test should go in the same directory as the interface under test
	is found in an SDK. For example:

	\| Tests for... \| Should go in... \|
	\|--------------\|-----------------\|
	\| Host tools \| //sdk/cts/tests/tools \|
	\| FIDL interfaces \| //sdk/cts/tests/fidl \|
	\| Libraries \| //sdk/cts/tests/pkg \|

	See existing tests under `//sdk/cts/tests` for examples.

	### Step 2: Create your test executable

	Note: The CTS build templates verify that dependencies are released in an SDK.
	If your test needs an exception, [file a bug] in `DeveloperExperience>CTS`. The
	allow list can be found [here](/sdk/cts/build/allowed_cts_deps.gni).

	In your test directory's `BUILD.gn` file, create a test executable using CTS
	build templates.

	* {C/C++}

	```gn
	import("//sdk/cts/build/cts.gni")

	cts_executable("my_test_binary") {
	deps = [ "//zircon/system/ulib/zxtest" ]
	sources = [ "my_test.cc" ]
	testonly = true
	}
	```

	* {Rust}

	```gn
	import("//sdk/cts/build/cts.gni")

	cts_rustc_test("my_test_binary") {
	edition = "2018"
	source_root = "src/my_test.rs"
	sources = [ "src/my_test.rs" ]
	}
	```

	### Step 3: Create your test component

	Note: This section assumes familiarity with the concept of [Test Components].

	```json5
	// my_test_component.cml
	{
	include: [
	// Select the appropriate test runner shard here:
	// rust, elf, etc.
	"//src/sys/test_runners/rust/default.shard.cml",
	],
	program: {
	binary: "bin/my_test_binary",
	},
	facets: {
	// mark your test type "cts".
	"fuchsia.test": { type: "cts" },
	},
	...
	}
	```

	Wrap your executable as a Fuchsia component. CTS provides a special GN template
	for creating a component:

	```gn
	cts_fuchsia_component("my_test_component") {
	testonly = true
	manifest = "meta/my_test_component.cml",
	deps = [ ":my_test_binary" ]
	}
	```

	### Step 4: Create your test package

	CTS also provides a special GN template for creating a test package:

	```gn
	cts_fuchsia_test_package("my_test") {
	package_name = "my_test"
	test_components = [ ":my_test_component" ]
	}
	```

	### Step 5: Run the test

	These instructions require you to open several terminal tabs.

	#### Tab 1: Start the Fuchsia package server

	```
	fx serve
	```

	#### Tab 2: Start the Fuchsia emulator

	```
	ffx emu start --headless
	```

	* `--headless` disables graphical output.

	For more information on configuring the emulator, see [Start the Fuchsia Emulator].

	#### Tab 3: Stream the device logs

	This step is useful for debugging your test.

	```
	ffx log
	```

	#### Tab 4: Run the test

	<pre class="prettyprint">
	<code class="devsite-terminal">fx set core.x64 --with <var>TARGET_LABEL</var> </code>
	<code class="devsite-terminal">fx test <var>TARGET_LABEL</var> # or fx test <var>TEST_NAME</var> </code>
	</pre>

	* `-v` enables verbose output.

	See the section about "Debugging tips" below.

	### Step 6. Verify your test passes as part of the CTS release

	This step involves building the CTS in the same way that our CI does when it is
	released, then running those CTS tests in your local checkout. It is necessary
	because upon release, we automatically rewrite each CTS test package's name to
	deduplicate it from the same package's name at HEAD (the build does not allow
	duplicate names) and we must verify that the test still passes after this
	rewrite.

	Follow the instructions in Step 4 to start an emulator and a package server,
	then launch a new terminal and run the following command:

	```
	$FUCHSIA_DIR/sdk/cts/build/scripts/verify_release/verify_release.py
	```

	This command will build the CTS archive, release it to your
	`//prebuilt/cts/test/*` directory, and run the tests contained therein. After
	a brief pause, the test results will be printed to the terminal window.

	To learn more about that script, or to run the commands manually, please see
	[//sdk/cts/build/scripts/verify_release/README.md](https://fuchsia.googlesource.com/fuchsia/+/refs/heads/main/sdk/cts/build/scripts/verify_release/README.md).

	Some common causes of test failure at this stage include:

	* The test launches one of its child components using an absolute component URL.
	* Explanation: The URL is no longer correct because the test's package was
	renamed.
	* Solution: Use a [relative component URL] instead.
	* The test is missing a dependency.
	* Explanation: It's possible that the Fuchsia system contained a different
	set of packages when you built and ran your test at HEAD vs as part of the CTS
	and that your test depended on some of those packages.
	* Solution: Make sure your test's GN target explicitly lists all of its
	direct dependencies as `deps`.

	If you need additional help debugging at this step, please reach out to the CTS
	team by filing a bug in the [CTS bug component].

	### Step 7. Make the test run on presubmit

	This step causes the version of your test from Fuchsia's HEAD commit to run as
	part of Fuchsia's presumbit queue. It does not include your test in the CTS
	release (See the next section).

	Add a "tests" group to your BUILD file:

	```
	group("tests") {
	testonly = true
	deps = [ ":my_test" ]
	}
	```

	Next add this target as a dependency to the closest ancestor `group("tests")`
	target.

	### Step 8. Make the test run as part of the CTS release

	This step includes your test in the CTS release, which guarantees that your test
	cannot be broken between Fuchsia milestone releases (typically made every six
	weeks).

	Add an `sdk_molecule` target and use it to mark all of your test packages for
	inclusion in CTS. Each `cts_*` template declares an `sdk_atom` or `sdk_molecule`
	target with the name `${target_name}_sdk`. List each of the test packages as
	dependencies:

	```
	sdk_molecule("test_sdks") {
	testonly = true
	deps = [ ":my_test_sdk" ]
	}
	```

	Next add this target as a dependency to the closest ancestor
	`sdk_molecule("test_sdks")`.

	Once these steps are complete, submit your change and you should see your test run
	as part of the next CTS release.

	### Debugging Tips

	* If your test hangs, use `ffx component list -v` to inspect its current state.

	## How to write a test for experimental FIDL

	The CTS supports writing tests for FIDL interfaces that are not yet released in
	the SDK. This allows you to write CTS tests for your API while you are still
	developing it. Writing tests using the CTS framework while you develop your API
	ensures that your tests do not depend on any non-SDK targets.

	### Step 1. Ensure your FIDL is marked as experimental
	Your FIDL interface should be marked with `sdk_category = "experimental"`. If
	your interface is marked as `public` or `partner`, follow the steps above to
	write a CTS test.

	```
	fidl("fuchsia.interface") {
	sdk_category = "experimental"
	name = "fuchsia.interface"
	sources = [ "interface.fidl" ]
	}
	```

	### Step 2. Add your FIDL to the CTS allow list
	The CTS verifies that its dependencies are in the SDK. To avoid build time
	errors, your FIDL must be added to the CTS [allow list].

	```
	# //sdk/cts/build/allowed_cts_deps.gni
	ALLOWED_EXPERIMENTAL_FIDL = [
	...,
	"//absolute/path/to/experimental:fidl"
	]
	```

	### Step 3. Follow the steps above to write an ABI test
	Follow the steps in the [How to write an ABI test](#how_to_write_an_abi_test)
	section to write an ABI test for your experimental FIDL.

	### Step 4. Mark your test package as experimental
	The CTS includes tests based on metadata generated by
	`cts_fuchsia_test_package`. To avoid generating this metadata (and including
	your test in the CTS), mark your test package with `uses_experimental_fidl`.

	```
	cts_fuchsia_test_package("my_experimental_test") {
	uses_experimental_fidl = true
	test_components = [ ":my_experimental_component" ]
	}
	```

	### Step 5. Release your CTS test
	When your FIDL interface is no longer experimental, release your CTS test!
	To release your CTS test, follow the steps in the
	[How to write an ABI test](#how_to_write_an_abi_test) section and delete the
	`uses_experimental_fidl` line from your `cts_fuchsia_test_package`.

	## How to remove an ABI test

	Please see the FAQ section about [retiring tests].

	## How to disable your test

	Please see the FAQ section about [disabling tests].

	[Component Manifests]: /docs/concepts/components/v2/component_manifests.md
	[Components]: /docs/concepts/components/v2
	[Fuchsia language policy]: /docs/contribute/governance/policy/programming_languages.md
	[Packages]: /docs/concepts/packages/package.md
	[Start the Fuchsia Emulator]: /docs/get-started/set_up_femu.md
	[Test Components]: /docs/development/testing/components/test_component.md
	[file a bug]: https://bugs.fuchsia.dev/p/fuchsia/issues/list?q=component%3ADeveloperExperience%3ECTS
	[relative component URL]: /docs/reference/components/url.md#relative
	[CTS bug component]: https://bugs.fuchsia.dev/p/fuchsia/templates/detail?saved=1&template=Fuchsia%20Compatibility%20Test%20Suite%20%28CTS%29&ts=1627669234
	[disabling tests]: /docs/development/testing/cts/faq.md#disable-a-test
	[retiring tests]: /docs/development/testing/cts/faq.md#retire-a-test
	[allow list]: /sdk/cts/build/allowed_cts_deps.gni