The black box testing framework enables an integration test to observe or influence the behavior of component manager without depending on its internal libraries.
Creating dependencies on component manager's internal libraries is problematic for a number of reasons:
To test the behavior of a component or a component manager feature, you must be able to write a black box test that can:
Note: The black box testing framework covers all of these points.
The testing framework provides two Rust libraries for black box testing:
BlackBoxTest
BreakpointSystemClient
BlackBoxTest
is a Rust library provided by the testing framework. You can use the classes and methods in this library to automate large parts of the setup needed for a black box test.
For the BlackBoxTest
library to function correctly, the integration test component manifest must specify (at minimum) the following features and services:
"sandbox": { "features": [ "hub" ], "services": [ "fuchsia.process.Launcher", "fuchsia.sys.Launcher", "fuchsia.sys.Environment", "fuchsia.logger.LogSink" ] }
These services and features ensure that BlackBoxTest
can set up a hermetic environment and launch component manager.
In the simplest case, a black box test looks like the following:
let test = BlackBoxTest::default("fuchsia-pkg://fuchsia.com/foo#meta/root.cm").await?;
By the end of this statement:
root.cm
) has been resolved.$out/hub
.BreakpointSystem
FIDL service at $out/svc/fuchsia.test.breakpoints.BreakpointSystem
.exec
directories for any component.The BreakpointSystem
FIDL service is used to set breakpoints and unblock component manager. This code demonstrates using the BreakpointSystem
service:
let breakpoint_system = test.connect_to_breakpoint_system().await?; let receiver = breakpoint_system.set_breakpoints(vec![StopInstance::TYPE]).await?; breakpoint_system.start_component_tree().await?;
By the end of this code block:
StopInstance
events.In some cases, you may want to customize BlackBoxTest::default
. BlackBoxTest::custom
allows you to specify:
The component manager manifest to be used for the test.
Additional directories to be created in component manager's namespace.
A file descriptor to redirect output from components.
let test = BlackBoxTest::custom( "fuchsia-pkg://fuchsia.com/my_custom_cm#meta/component_manager.cmx", "fuchsia-pkg://fuchsia.com/foo#meta/root.cm", vec![("my_dir", my_dir_handle)], output_file_descriptor ).await?;
The BlackBoxTest
library also provides convenience methods for starting up component manager and expecting a particular output:
launch_component_and_expect_output( "fuchsia-pkg://fuchsia.com/echo#meta/echo.cm", "Hippos rule!", ).await?;
The breakpoint system addresses the problem of verifying state in component manager and is analogous to a debugger's breakpoint system.
Since the breakpoint system is built on top of system events:
Note: When component manager is in debug mode, the breakpoint system is installed at the root. Hence it receives events from all components.
For reliable state verification, a test must be able to:
The workflow for the BreakpointSystemClient
library looks something like this:
// Create a BreakpointSystemClient using ::new() or use the client // provided by BlackBoxTest let test = BlackBoxTest::default("fuchsia-pkg://fuchsia.com/foo#meta/root.cm").await?; // Get a receiver by setting breakpoints let breakpoint_system = test.connect_to_breakpoint_system().await?; let receiver = breakpoint_system.set_breakpoints(vec![BeforeStartInstance::TYPE]).await?; // Unblock component manager breakpoint_system.start_component_tree().await?; // Wait for an invocation let invocation = receiver.expect_type::<BeforeStartInstance>().await?; // Verify state ... // Resume from invocation invocation.resume().await?;
With complex component hierarchies, event propagation is hard to predict and may even be non-deterministic due to the asynchronous nature of component manager. To deal with these cases, breakpoints offer the following additional functionality:
It is possible to register multiple receivers, each listening to their own set of events:
// BeforeStartInstance and RouteCapability events can be interleaved, // so use different receivers. let start_receiver = breakpoint_system.set_breakpoints(vec![BeforeStartInstance::TYPE]).await?; let route_receiver = breakpoint_system.set_breakpoints(vec![RouteCapability::TYPE]).await?; // Expect 5 components to start for _ in 1..=5 { let invocation = start_receiver.expect_type::<BeforeStartInstance>().await?; invocation.resume().await?; } // Expect a RouteCapability event from /foo:0 let invocation = route_receiver.expect_exact::<RouteCapability>("/foo:0").await?; invocation.resume().await?;
It is possible to listen for specific invocations and then discard the receiver, causing future invocations to be ignored:
// Set a breakpoint on StopInstance events let stop_receiver = breakpoint_system.set_breakpoints(vec![StopInstance::TYPE]).await?; { // Temporarily set a breakpoint on RouteCapability events let use_receiver = breakpoint_system.set_breakpoints(vec![RouteCapability::TYPE]).await?; // Expect a RouteCapability event from /bar:0 let invocation = route_receiver.expect_exact::<RouteCapability>("/bar:0").await?; println!("/bar:0 used capability -> {}", invocation.capability_id); invocation.resume().await?; } // At this point, the test does not care about RouteCapability events, so the receiver // can be dropped. If the receiver were left instantiated, component manager would // halt on future RouteCapability events. // Expect a StopInstance event let invocation = stop_receiver.expect_type::<StopInstance>().await?; println!("{} was stopped!", invocation.target_moniker); invocation.resume().await?;
Several tests need to communicate with components directly. It is often also desirable to mock out capabilities that a component connects to in the test. The simplest way to do this is to implement an Injector
.
/// Client <---> EchoCapability /// EchoCapability implements the Echo protocol and responds to clients. struct EchoCapability; #[async_trait] impl Injector for EchoCapability { type Marker = fecho::EchoMarker; async fn serve(self: Arc<Self>, mut request_stream: fecho::EchoRequestStream) { // Start listening to requests from client while let Some(Ok(fecho::EchoRequest::EchoString { value: Some(input), responder })) = request_stream.next().await { // Respond to the client with the echo string. responder.send(Some(&input)).expect("failed to send echo response"); } } }
It is possible to listen for a RouteCapability
event and install the injector:
// Create the server end of EchoService let echo_capability = EchoCapability::new(); // Set a breakpoint on RouteCapability events let receiver = breakpoint_system.set_breakpoints(vec![RouteCapability::TYPE]).await?; // Wait until /foo:0 attempts to connect to the EchoService component capability let invocation = receiver.wait_until_component_capability( "/foo:0", "/svc/fuchsia.echo.EchoService", ).await?; invocation.inject(echo_capability).await?; // Resume from the invocation invocation.resume().await?;
Alternatively, the BreakpointSystem
can automatically install an injector matching the capability requested by any component in the test.
let echo_capability = EchoCapability::new(); breakpoint_system.install_injector(echo_capability).await?; // Set up other breakpoints. breakpoint_system.start_component_tree().await?;
Tests may want to silently observe or mutate messages between a client and service. It is possible to interpose a capability and manipulate the traffic over the channel. Consider an interposer for an Echo service that mutates the input from the client before sending it to the service:
/// Client <---> EchoInterposer <---> Echo service /// The EchoInterposer copies all echo responses from the service /// and sends them over an mpsc::Channel to the test. struct EchoInterposer; #[async_trait] impl Interposer for EchoInterposer { type Marker = fecho::EchoMarker; async fn interpose( self: Arc<Self>, mut from_client: fecho::EchoRequestStream, to_service: fecho::EchoProxy, ) { // Start listening to requests from client while let Some(Ok(fecho::EchoRequest::EchoString { value: Some(input), responder })) = from_client.next().await { // Copy the response from the service and send it to the test let modified_input = format!("{} Let there be chaos!", input); // Forward the request to the service and get a response let out = to_service .echo_string(Some(&modified_input)) .await .expect("echo_string failed") .expect("echo_string got empty result"); // Respond to the client with the response from the service responder.send(Some(out.as_str())).expect("failed to send echo response"); } } }
The test can use EchoInterposer
on any RouteCapability
event:
// Wait for echo_looper to attempt to connect to the Echo service let invocation = receiver .wait_until_component_capability("/echo_looper:0", "/svc/fidl.examples.routing.echo.Echo") .await?; // Setup the interposer let (interposer, mut rx) = EchoInterposer::new(); invocation.interpose(interposer).await?; invocation.resume().await?;
Alternatively, the BreakpointSystem
can automatically install an interposer matching the capability requested by any component in the test.
let (interposer, mut rx) = EchoInterposer::new(); breakpoint_system.install_interposer(interposer).await?; // Set up other breakpoints. breakpoint_system.start_component_tree().await?;
It is possible to soak up events of certain types and drain them at a later point in time:
let receiver = breakpoint_system.set_breakpoints(vec![PostDestroyInstance::TYPE]).await?; let sink = breakpoint_system.soak_events(vec![BeforeStartInstance::TYPE]).await?; // Wait for the root component to be destroyed let invocation = receiver.expect_exact::<PostDestroyInstance>("/").await?; invocation.resume().await?; // Drain events from the sink let events = sink.drain().await; // Verify that the 3 components were started in the correct order assert_eq!(events, vec![ DrainedEvent { event_type: BeforeStartInstance::TYPE, target_moniker: "/".to_string() }, DrainedEvent { event_type: BeforeStartInstance::TYPE, target_moniker: "/foo:0".to_string() }, DrainedEvent { event_type: BeforeStartInstance::TYPE, target_moniker: "/foo:0/bar:0".to_string() } ]);
Both BlackBoxTest
and BreakpointSystemClient
rely on component manager’s debug mode.
To start component manager in debug mode, pass in --debug
as an additional argument to the component_manager.cmx
component. In fact, this is exactly what BlackBoxTest::default
does when setting up a black box test.
When component manager is in debug mode, it does the following:
Creates the root realm and built-in services.
Creates the hub and the breakpoint system.
Serves the following from component manager's outgoing directory:
The hub of the root component at $out/hub
.
The BreakpointSystem
FIDL service at $out/svc/fuchsia.test.breakpoints.BreakpointSystem
.
Waits to be unblocked by the BreakpointSystem
FIDL service.
Starts up the root component (including any eager children).