Test harness to support testing of Amethyst types, including:

• Bundle
• State
• System
• Resource loading.
• Arbitrary types that Systems use during processing.

The test harness minimizes boilerplate code to set up an Amethyst Application with common bundles, and can take in logic that is normally masked behind a number of layers through a thin interface.

Usage

The following shows a simple example of testing a State. More examples are in the Examples section.

# use std::marker::PhantomData;
#
# use amethyst_test::prelude::*;
# use amethyst::{
#     ecs::prelude::*,
#     prelude::*,
# };
#
# #[derive(Debug)]
# struct LoadResource;
#
# #[derive(Debug)]
# struct LoadingState;
#
# impl LoadingState {
#     fn new() -> Self {
#         LoadingState
#     }
# }
#
# impl<'a, 'b, E> State<GameData<'a, 'b>, E> for LoadingState
# where
#     E: Send + Sync + 'static,
# {
#     fn update(&mut self, data: StateData<'_, GameData<'_, '_>>) -> Trans<GameData<'a, 'b>, E> {
#         data.data.update(&data.world);
#
#         data.world.insert(LoadResource);
#
#         Trans::Pop
#     }
# }
#
// #[test]
fn loading_state_adds_load_resource() {
assert!(
AmethystApplication::blank()
.with_state(|| LoadingState::new())
.with_assertion(|world| {
world.read_resource::<LoadResource>();
})
.run()
.is_ok()
);
}
#
# fn main() {
#     loading_state_adds_load_resource();
# }

The Amethyst application is initialized with one of the following functions, each providing a different set of bundles:

use amethyst_test::prelude::*;

#[test]
fn test_name() {
// Start with no bundles
AmethystApplication::blank();

// Start with the following bundles:
//
// * `TransformBundle`
// * `InputBundle`
// * `UiBundle`
//
// The type parameters here are the Axis and Action types for the
// `InputBundle` and `UiBundle`.
use amethyst::input::StringBindings;
AmethystApplication::ui_base::<StringBindings>();

// If you need types from the rendering bundle, make sure you have
// the `"test-support"` feature enabled:
//
// ```toml
// # Cargo.toml
// amethyst = { version = "..", features = ["test-support"] }
// ```
//
// Then you can include the `RenderEmptyBundle`:
use amethyst::renderer::{types::DefaultBackend, RenderEmptyBundle};
AmethystApplication::blank()
.with_bundle(RenderEmptyBundle::<DefaultBackend>::new());
}

Next, attach the logic you wish to test using the various .with_*(..) methods:

# use amethyst::{
#     core::bundle::SystemBundle,
#     ecs::prelude::*,
#     prelude::*,
# };
#
# #[derive(Debug)]
# struct MySystem;
#
# impl<'s> System<'s> for MySystem {
#     type SystemData = ();
#     fn run(&mut self, _: Self::SystemData) {}
# }
#
#[test]
fn test_name() {
let visibility = false; // Whether the window should be shown
AmethystApplication::render_base::<String, String, _>("test_name", visibility)
.with_bundle(MyBundle::new())                // Registers a bundle.
.with_bundle_fn(|| MyNonSendBundle::new())   // Registers a `!Send` bundle.
.with_resource(MyResource::new())            // Adds a resource to the world.
.with_system(MySystem, "my_sys", &[])        // Registers a system with the main
// dispatcher.

// These are run in the order they are invoked.
// You may invoke them multiple times.
.with_setup(|world| { /* do something */ })
.with_state(|| MyState::new())
.with_effect(|world| { /* do something */ })
.with_assertion(|world| { /* do something */ })
// ...
}

Finally, call .run() to run the application. This returns amethyst::Result<()>, so you can wrap it in an assert!(..);:

#[test]
fn test_name() {
let visibility = false; // Whether the window should be shown
assert!(
AmethystApplication::render_base("test_name", visibility)
// ...
.run()
.is_ok()
);
}

Examples

Testing a bundle:

# use amethyst_test::prelude::*;
# use amethyst::{
#     core::bundle::SystemBundle,
#     ecs::prelude::*,
#     prelude::*,
# };
#
# #[derive(Debug)]
# struct ApplicationResource;
#
# #[derive(Debug)]
# struct MySystem;
#
# impl<'s> System<'s> for MySystem {
#     type SystemData = ReadExpect<'s, ApplicationResource>;
#
#     fn run(&mut self, _: Self::SystemData) {}
# }
#
# #[derive(Debug)]
# struct MyBundle;
# impl<'a, 'b> SystemBundle<'a, 'b> for MyBundle {
#     fn build(self, world: &mut World, builder: &mut DispatcherBuilder<'a, 'b>)
#     -> amethyst::Result<()> {
#         world.insert(ApplicationResource);
#         builder.add(MySystem, "my_system", &[]);
#         Ok(())
#     }
# }
#
// #[test]
fn bundle_registers_system_with_resource() {
assert!(
AmethystApplication::blank()
.with_bundle(MyBundle)
.with_assertion(|world| { world.read_resource::<ApplicationResource>(); })
.run()
.is_ok()
);
}
#
# fn main() {
#     bundle_registers_system_with_resource();
# }

Testing a system:

# use amethyst_test::prelude::*;
# use amethyst::{
#     ecs::prelude::*,
#     prelude::*,
# };
#
# struct MyComponent(pub i32);
#
# impl Component for MyComponent {
#     type Storage = DenseVecStorage<Self>;
# }
#
# #[derive(Debug)]
# struct MySystem;
#
# impl<'s> System<'s> for MySystem {
#     type SystemData = WriteStorage<'s, MyComponent>;
#
#     fn run(&mut self, mut my_component_storage: Self::SystemData) {
#         for mut my_component in (&mut my_component_storage).join() {
#             my_component.0 += 1
#         }
#     }
# }
#
// #[test]
fn system_increases_component_value_by_one() {
assert!(
AmethystApplication::blank()
.with_system(MySystem, "my_system", &[])
.with_effect(|world| {
let entity = world.create_entity().with(MyComponent(0)).build();
world.insert(EffectReturn(entity));
})
.with_assertion(|world| {
let entity = world.read_resource::<EffectReturn<Entity>>().0.clone();

let my_component_storage = world.read_storage::<MyComponent>();
let my_component = my_component_storage
.get(entity)
.expect("Entity should have a `MyComponent` component.");

// If the system ran, the value in the `MyComponent` should be 1.
assert_eq!(1, my_component.0);
})
.run()
.is_ok()
);
}
#
# fn main() {
#     system_increases_component_value_by_one();
# }

Testing a System in a custom dispatcher. This is useful when your system must run after some setup has been done:

# use amethyst_test::prelude::*;
# use amethyst::{
#     ecs::prelude::*,
#     prelude::*,
# };
#
# // !Default
# struct MyResource(pub i32);
#
# #[derive(Debug)]
# struct MySystem;
#
# impl<'s> System<'s> for MySystem {
#     type SystemData = WriteExpect<'s, MyResource>;
#
#     fn run(&mut self, mut my_resource: Self::SystemData) {
#         my_resource.0 += 1
#     }
# }
#
// #[test]
fn system_increases_resource_value_by_one() {
assert!(
AmethystApplication::blank()
.with_setup(|world| {
world.insert(MyResource(0));
})
.with_system_single(MySystem, "my_system", &[])
.with_assertion(|world| {
let my_resource = world.read_resource::<MyResource>();

// If the system ran, the value in the `MyResource` should be 1.
assert_eq!(1, my_resource.0);
})
.run()
.is_ok()
);
}
#
# fn main() {
#     system_increases_resource_value_by_one();
# }