build/config/fuchsia/test/README.md

## Manifest Fragments

This directory contains the manifest fragments that are required for running
Fuchsia tests hermetically. Tests start from `minimum.shard.test-cml` and add
additional capabilities as necessary by providing the
`additional_manifest_fragments` argument. Some fragments are explained in detail
below:

### General Purpose Fragments

#### archivist.shard.test-cml
Runs an `archivist-for-embedding` with custom protocol routing for tests
that want to intercept events written to a `LogSink` by a component.

#### chromium_test_facet.shard.test-cml
Runs tests in the `chromium` test realm, which is mostly hermetic but has
access to specific system services that cannot (currently) be faked. For more
information, see https://fxbug.dev/91934. This is generally required for all
Chromium tests not using the
[`chromium_system_test_facet`](#chromium_system_test_facetshardtest-cml).

#### fonts.shard.test-cml
For tests that need `fuchsia.fonts.Provider` to provide a basic set of fonts.
This shard runs an isolated font provider with fonts bundled into the fonts
package.

#### test_fonts.shard.test-cml
For tests that need `fuchsia.fonts.Provider` to provide a specific set of fonts
(beyond that provided by `fonts.shard.test-cml`). This shard requires fonts to
be provided as a directory. The directory must be named `config-data`, must
contain the file named `all_font_manifest.json`, and all the font files named
in it. For details see the [font manifest][fm] in Fuchsia documentation.

[fm]: https://fuchsia.dev/fuchsia-src/development/internationalization/fonts/build?hl=en#:font_collection-outputs

The user of this shard must provide a directory `/pkg/test_fonts`, which must
contain all the files described above.

Within Chromium, these fonts are usually provided via the target
`//skia:test_fonts`.

#### mark_vmo_executable.shard.test-cml
Required by tests that execute JavaScript. Should only be required in a small
number of tests.

#### minimum.shard.test-cml
Capabilities required by anything that uses `//base/test` when running in the
(default) `chromium` test realm. It is the default base fragment for most
`test()` Components.

#### logger.shard.test-cml
For tests that test logging functionality by providing `fuchsia.logger.Log`.

#### sysmem.shard.test-cml
For tests that depend on the sysmem service (e.g. to allocate image buffers to
share with Vulkan and Scenic).

#### system_test_minimum.shard.test-cml
Capabilities required by anything that uses `//base/test` when running as a
system test in the `chromium-system` test realm. It is the base fragment for
`test()` Components that use the
[`chromium_system_test_facet`](#chromium_system_test_facetshardtest-cml).

Most tests use the [`minimum`](#minimumshardtest-cml) shard.

#### chromium_system_test_facet.shard.test-cml
Runs tests in the `chromium-system` test realm. This is required for Chromium
tests that are intended to run against the actual system and its real system
services. This is required for, for example, performance tests intended to
measure system performance. Another overlapping use case is tests that need to
be run in environments without access to the packages containing fake
implementations of required protocols that other tests use.
(https://crbug.com/1408597 should make that use case obsolete.)

Most tests should use the
[`chromium_test_facet`](#chromium_test_facetshardtest-cml).

#### test_ui_stack.shard.test-cml
For tests that need an isolated UI subsystem, that supports the Flatland
API set.  This allows tests to e.g. run with view-focus unaffected by any
other tests running concurrently on the device, as well as providing test-only
functionality such as input-injection support.

### WebEngine Fragments
The following fragments are specific to WebEngine functionality as documented
documentation at
https://fuchsia.dev/reference/fidl/fuchsia.web#CreateContextParams and
https://fuchsia.dev/reference/fidl/fuchsia.web#ContextFeatureFlags.
Any test-specific exceptions are documented for each file.

#### audio_output.shard.test-cml
Required by tests that need to enable audio output.

#### platform_video_codecs.shard.test-cml
Required by tests that need accelerated (e.g., hardware) video codecs. A private
(semi-isolated) instance of codec_factory is run for tests using this shard in
support of running on system images that don't run it.

#### network.shard.test-cml
For tests that need access to network services, including those that access a
local HTTP server.

#### network.shard.test-cml
Corresponds to the `NETWORK` flag. Required for enabling network access. Note
that access to the root SSL certificates is not needed if ContextProvider is
used to launch the `Context`. The `fuchsia.device.NameProvider` dependency comes
from fdio.

#### present_view.shard.test-cml
Services that are needed to render web content in a Scenic view and present it.
Most services are required per the FIDL documentation.

#### web_instance.shard.test-cml
Contains services that need to be present when creating a `fuchsia.web.Context`.
Note that the `fuchsia.scheduler.ProfileProvider` service is only used in tests
that encounter memory pressure code.