Introduce a gpui2::test macro

Co-Authored-By: Conrad Irwin <conrad.irwin@gmail.com>
Co-Authored-By: Max Brunsfeld <max@zed.dev>
Co-Authored-By: Kyle <kyle@zed.dev>

crates/gpui2/src/gpui2.rs

@@ -17,6 +17,8 @@ mod styled;
 mod subscription;
 mod svg_renderer;
 mod taffy;
+#[cfg(any(test, feature = "test-support"))]
+mod test;
 mod text_system;
 mod util;
 mod view;
@@ -48,6 +50,8 @@ pub use styled::*;
 pub use subscription::*;
 pub use svg_renderer::*;
 pub use taffy::{AvailableSpace, LayoutId};
+#[cfg(any(test, feature = "test-support"))]
+pub use test::*;
 pub use text_system::*;
 pub use util::arc_cow::ArcCow;
 pub use view::*;

crates/gpui2/src/platform/test/dispatcher.rs

@@ -75,6 +75,10 @@ impl TestDispatcher {
             count: self.state.lock().random.gen_range(0..10),
         }
     }
+
+    pub fn run_until_parked(&self) {
+        while self.poll() {}
+    }
 }
 
 impl Clone for TestDispatcher {

crates/gpui2/src/test.rs

@@ -0,0 +1,51 @@
+use crate::TestDispatcher;
+use rand::prelude::*;
+use std::{
+    env,
+    panic::{self, RefUnwindSafe},
+};
+
+pub fn run_test(
+    mut num_iterations: u64,
+    max_retries: usize,
+    test_fn: &mut (dyn RefUnwindSafe + Fn(TestDispatcher)),
+    on_fail_fn: Option<fn()>,
+    _fn_name: String, // todo!("re-enable fn_name")
+) {
+    let starting_seed = env::var("SEED")
+        .map(|seed| seed.parse().expect("invalid SEED variable"))
+        .unwrap_or(0);
+    let is_randomized = num_iterations > 1;
+    if let Ok(iterations) = env::var("ITERATIONS") {
+        num_iterations = iterations.parse().expect("invalid ITERATIONS variable");
+    }
+
+    for seed in starting_seed..starting_seed + num_iterations {
+        let mut retry = 0;
+        loop {
+            if is_randomized {
+                eprintln!("seed = {seed}");
+            }
+            let result = panic::catch_unwind(|| {
+                let dispatcher = TestDispatcher::new(StdRng::seed_from_u64(seed));
+                test_fn(dispatcher);
+            });
+
+            match result {
+                Ok(_) => break,
+                Err(error) => {
+                    if retry < max_retries {
+                        println!("retrying: attempt {}", retry);
+                        retry += 1;
+                    } else {
+                        if is_randomized {
+                            eprintln!("failing seed: {}", seed);
+                        }
+                        on_fail_fn.map(|f| f());
+                        panic::resume_unwind(error);
+                    }
+                }
+            }
+        }
+    }
+}