diff --git a/crates/wiggle/test-helpers/examples/tracing.rs b/crates/wiggle/test-helpers/examples/tracing.rs
index fe2dd51d8e..1e1517d8d9 100644
--- a/crates/wiggle/test-helpers/examples/tracing.rs
+++ b/crates/wiggle/test-helpers/examples/tracing.rs
@@ -24,7 +24,6 @@ witx_literal: "
      (param $s $s)
      (result $err (expected $t (error $errno)))))
     ",
-    ctx: WasiCtx,
     errors: { errno => RichError },
 });
 
diff --git a/crates/wiggle/tests/atoms.rs b/crates/wiggle/tests/atoms.rs
index b39bec5b15..9aabbc74c5 100644
--- a/crates/wiggle/tests/atoms.rs
+++ b/crates/wiggle/tests/atoms.rs
@@ -4,7 +4,6 @@ use wiggle_test::{impl_errno, HostMemory, MemArea, WasiCtx};
 
 wiggle::from_witx!({
     witx: ["$CARGO_MANIFEST_DIR/tests/atoms.witx"],
-    ctx: WasiCtx,
 });
 
 impl_errno!(types::Errno, types::GuestErrorConversion);
diff --git a/crates/wiggle/tests/atoms_async.rs b/crates/wiggle/tests/atoms_async.rs
new file mode 100644
index 0000000000..5fe20b326b
--- /dev/null
+++ b/crates/wiggle/tests/atoms_async.rs
@@ -0,0 +1,139 @@
+use proptest::prelude::*;
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
+use wiggle::GuestMemory;
+use wiggle_test::{impl_errno, HostMemory, MemArea, WasiCtx};
+
+wiggle::from_witx!({
+    witx: ["$CARGO_MANIFEST_DIR/tests/atoms.witx"],
+    async_: {
+        atoms::{int_float_args, double_int_return_float}
+    }
+});
+
+impl_errno!(types::Errno, types::GuestErrorConversion);
+
+#[wiggle::async_trait(?Send)]
+impl<'a> atoms::Atoms for WasiCtx<'a> {
+    async fn int_float_args(&self, an_int: u32, an_float: f32) -> Result<(), types::Errno> {
+        println!("INT FLOAT ARGS: {} {}", an_int, an_float);
+        Ok(())
+    }
+    async fn double_int_return_float(
+        &self,
+        an_int: u32,
+    ) -> Result<types::AliasToFloat, types::Errno> {
+        Ok((an_int as f32) * 2.0)
+    }
+}
+
+// There's nothing meaningful to test here - this just demonstrates the test machinery
+
+#[derive(Debug)]
+struct IntFloatExercise {
+    pub an_int: u32,
+    pub an_float: f32,
+}
+
+impl IntFloatExercise {
+    pub fn test(&self) {
+        let ctx = WasiCtx::new();
+        let host_memory = HostMemory::new();
+
+        let e = run(atoms::int_float_args(
+            &ctx,
+            &host_memory,
+            self.an_int as i32,
+            self.an_float,
+        ));
+
+        assert_eq!(e, Ok(types::Errno::Ok as i32), "int_float_args error");
+    }
+
+    pub fn strat() -> BoxedStrategy<Self> {
+        (prop::num::u32::ANY, prop::num::f32::ANY)
+            .prop_map(|(an_int, an_float)| IntFloatExercise { an_int, an_float })
+            .boxed()
+    }
+}
+
+proptest! {
+    #[test]
+    fn int_float_exercise(e in IntFloatExercise::strat()) {
+        e.test()
+    }
+}
+#[derive(Debug)]
+struct DoubleIntExercise {
+    pub input: u32,
+    pub return_loc: MemArea,
+}
+
+impl DoubleIntExercise {
+    pub fn test(&self) {
+        let ctx = WasiCtx::new();
+        let host_memory = HostMemory::new();
+
+        let e = run(atoms::double_int_return_float(
+            &ctx,
+            &host_memory,
+            self.input as i32,
+            self.return_loc.ptr as i32,
+        ));
+
+        let return_val = host_memory
+            .ptr::<types::AliasToFloat>(self.return_loc.ptr)
+            .read()
+            .expect("failed to read return");
+        assert_eq!(e, Ok(types::Errno::Ok as i32), "errno");
+        assert_eq!(return_val, (self.input as f32) * 2.0, "return val");
+    }
+
+    pub fn strat() -> BoxedStrategy<Self> {
+        (prop::num::u32::ANY, HostMemory::mem_area_strat(4))
+            .prop_map(|(input, return_loc)| DoubleIntExercise { input, return_loc })
+            .boxed()
+    }
+}
+
+proptest! {
+    #[test]
+    fn double_int_return_float(e in DoubleIntExercise::strat()) {
+        e.test()
+    }
+}
+
+fn run<F: Future>(future: F) -> F::Output {
+    let mut f = Pin::from(Box::new(future));
+    let waker = dummy_waker();
+    let mut cx = Context::from_waker(&waker);
+    loop {
+        match f.as_mut().poll(&mut cx) {
+            Poll::Ready(val) => break val,
+            Poll::Pending => {}
+        }
+    }
+}
+
+fn dummy_waker() -> Waker {
+    return unsafe { Waker::from_raw(clone(5 as *const _)) };
+
+    unsafe fn clone(ptr: *const ()) -> RawWaker {
+        assert_eq!(ptr as usize, 5);
+        const VTABLE: RawWakerVTable = RawWakerVTable::new(clone, wake, wake_by_ref, drop);
+        RawWaker::new(ptr, &VTABLE)
+    }
+
+    unsafe fn wake(ptr: *const ()) {
+        assert_eq!(ptr as usize, 5);
+    }
+
+    unsafe fn wake_by_ref(ptr: *const ()) {
+        assert_eq!(ptr as usize, 5);
+    }
+
+    unsafe fn drop(ptr: *const ()) {
+        assert_eq!(ptr as usize, 5);
+    }
+}
diff --git a/crates/wiggle/tests/errors.rs b/crates/wiggle/tests/errors.rs
index 53d39a233d..ec9291ff53 100644
--- a/crates/wiggle/tests/errors.rs
+++ b/crates/wiggle/tests/errors.rs
@@ -23,7 +23,6 @@ mod convert_just_errno {
      (param $strike u32)
      (result $err (expected (error $errno)))))
     ",
-        ctx: WasiCtx,
         errors: { errno => RichError },
     });
 
@@ -133,7 +132,6 @@ mod convert_multiple_error_types {
      (param $drink u32)
      (@witx noreturn)))
     ",
-        ctx: WasiCtx,
         errors: { errno => RichError, errno2 => AnotherRichError },
     });
 
diff --git a/crates/wiggle/tests/flags.rs b/crates/wiggle/tests/flags.rs
index b97285a94a..1a1f98c6c5 100644
--- a/crates/wiggle/tests/flags.rs
+++ b/crates/wiggle/tests/flags.rs
@@ -5,7 +5,6 @@ use wiggle_test::{impl_errno, HostMemory, MemArea, WasiCtx};
 
 wiggle::from_witx!({
     witx: ["$CARGO_MANIFEST_DIR/tests/flags.witx"],
-    ctx: WasiCtx,
 });
 
 impl_errno!(types::Errno, types::GuestErrorConversion);
diff --git a/crates/wiggle/tests/handles.rs b/crates/wiggle/tests/handles.rs
index d562e0bb14..15fb0d36be 100644
--- a/crates/wiggle/tests/handles.rs
+++ b/crates/wiggle/tests/handles.rs
@@ -6,7 +6,6 @@ const FD_VAL: u32 = 123;
 
 wiggle::from_witx!({
     witx: ["$CARGO_MANIFEST_DIR/tests/handles.witx"],
-    ctx: WasiCtx,
 });
 
 impl_errno!(types::Errno, types::GuestErrorConversion);
diff --git a/crates/wiggle/tests/ints.rs b/crates/wiggle/tests/ints.rs
index d09615cca6..23310ee561 100644
--- a/crates/wiggle/tests/ints.rs
+++ b/crates/wiggle/tests/ints.rs
@@ -5,7 +5,6 @@ use wiggle_test::{impl_errno, HostMemory, MemArea, WasiCtx};
 
 wiggle::from_witx!({
     witx: ["$CARGO_MANIFEST_DIR/tests/ints.witx"],
-    ctx: WasiCtx,
 });
 
 impl_errno!(types::Errno, types::GuestErrorConversion);
diff --git a/crates/wiggle/tests/keywords.rs b/crates/wiggle/tests/keywords.rs
index 1aa84e188a..fb93d7b3b3 100644
--- a/crates/wiggle/tests/keywords.rs
+++ b/crates/wiggle/tests/keywords.rs
@@ -13,7 +13,6 @@ mod enum_test {
                      $2big
                  )
              )",
-        ctx: DummyCtx,
     });
 }
 
@@ -31,7 +30,6 @@ mod module_trait_fn_and_arg_test {
                      (param $virtual u32)
                  )
              )",
-        ctx: WasiCtx,
     });
     impl<'a> self_::Self_ for WasiCtx<'a> {
         #[allow(unused_variables)]
@@ -51,7 +49,6 @@ mod struct_test {
                      (field $mut s32)
                  )
              )",
-        ctx: DummyCtx,
     });
 }
 
@@ -59,6 +56,5 @@ mod struct_test {
 mod union_test {
     wiggle::from_witx!({
         witx: ["$CARGO_MANIFEST_DIR/tests/keywords_union.witx"],
-        ctx: DummyCtx,
     });
 }
diff --git a/crates/wiggle/tests/lists.rs b/crates/wiggle/tests/lists.rs
index dd6f92c5d3..d2f76fd152 100644
--- a/crates/wiggle/tests/lists.rs
+++ b/crates/wiggle/tests/lists.rs
@@ -4,7 +4,6 @@ use wiggle_test::{impl_errno, HostMemory, MemArea, MemAreas, WasiCtx};
 
 wiggle::from_witx!({
     witx: ["$CARGO_MANIFEST_DIR/tests/lists.witx"],
-    ctx: WasiCtx,
 });
 
 impl_errno!(types::Errno, types::GuestErrorConversion);
diff --git a/crates/wiggle/tests/pointers.rs b/crates/wiggle/tests/pointers.rs
index ebae550fc3..96e33a734d 100644
--- a/crates/wiggle/tests/pointers.rs
+++ b/crates/wiggle/tests/pointers.rs
@@ -4,7 +4,6 @@ use wiggle_test::{impl_errno, HostMemory, MemArea, WasiCtx};
 
 wiggle::from_witx!({
     witx: ["$CARGO_MANIFEST_DIR/tests/pointers.witx"],
-    ctx: WasiCtx,
 });
 
 impl_errno!(types::Errno, types::GuestErrorConversion);
diff --git a/crates/wiggle/tests/records.rs b/crates/wiggle/tests/records.rs
index be44a44afc..fa448c3dc3 100644
--- a/crates/wiggle/tests/records.rs
+++ b/crates/wiggle/tests/records.rs
@@ -4,7 +4,6 @@ use wiggle_test::{impl_errno, HostMemory, MemArea, MemAreas, WasiCtx};
 
 wiggle::from_witx!({
     witx: ["$CARGO_MANIFEST_DIR/tests/records.witx"],
-    ctx: WasiCtx,
 });
 
 impl_errno!(types::Errno, types::GuestErrorConversion);
diff --git a/crates/wiggle/tests/strings.rs b/crates/wiggle/tests/strings.rs
index 0caeb73782..420a5c0a62 100644
--- a/crates/wiggle/tests/strings.rs
+++ b/crates/wiggle/tests/strings.rs
@@ -4,7 +4,6 @@ use wiggle_test::{impl_errno, HostMemory, MemArea, MemAreas, WasiCtx};
 
 wiggle::from_witx!({
     witx: ["$CARGO_MANIFEST_DIR/tests/strings.witx"],
-    ctx: WasiCtx,
 });
 
 impl_errno!(types::Errno, types::GuestErrorConversion);
diff --git a/crates/wiggle/tests/variant.rs b/crates/wiggle/tests/variant.rs
index 364fbbf7cf..5bddfb6aab 100644
--- a/crates/wiggle/tests/variant.rs
+++ b/crates/wiggle/tests/variant.rs
@@ -4,7 +4,6 @@ use wiggle_test::{impl_errno, HostMemory, MemArea, WasiCtx};
 
 wiggle::from_witx!({
     witx: ["$CARGO_MANIFEST_DIR/tests/variant.witx"],
-    ctx: WasiCtx,
 });
 
 impl_errno!(types::Errno, types::GuestErrorConversion);
diff --git a/crates/wiggle/tests/wasi.rs b/crates/wiggle/tests/wasi.rs
index 95c1461526..6dc6d84ea5 100644
--- a/crates/wiggle/tests/wasi.rs
+++ b/crates/wiggle/tests/wasi.rs
@@ -8,7 +8,6 @@ use wiggle_test::WasiCtx;
 
 wiggle::from_witx!({
     witx: ["$CARGO_MANIFEST_DIR/tests/wasi.witx"],
-    ctx: WasiCtx,
 });
 
 // The only test in this file is to verify that the witx document provided by the