Add pico_async_context_test

Currently just one regression test.

test/CMakeLists.txt

@@ -13,4 +13,5 @@ if (PICO_ON_DEVICE)
     add_subdirectory(cmsis_test)
     add_subdirectory(pico_sem_test)
     add_subdirectory(pico_sha256_test)
+    add_subdirectory(pico_async_context_test)
 endif()

test/pico_async_context_test/BUILD.bazel

@@ -0,0 +1,15 @@
+load("//bazel:defs.bzl", "compatible_with_rp2")
+
+package(default_visibility = ["//visibility:public"])
+
+cc_binary(
+    name = "pico_async_context_test",
+    testonly = True,
+    srcs = ["pico_async_context_test.c"],
+    target_compatible_with = compatible_with_rp2(),
+    deps = [
+        "//src/rp2_common/pico_stdlib",
+        "//src/rp2_common/pico_async_context:pico_async_context_threadsafe_background",
+        "//test/pico_test",
+    ],
+)

test/pico_async_context_test/CMakeLists.txt

@@ -0,0 +1,10 @@
+if (TARGET pico_async_context_threadsafe_background)
+    add_executable(pico_async_context_test
+        pico_async_context_test.c
+    )
+    target_link_libraries(pico_async_context_test PRIVATE
+        pico_test
+        pico_async_context_threadsafe_background
+    )
+    pico_add_extra_outputs(pico_async_context_test)
+endif()

test/pico_async_context_test/pico_async_context_test.c

@@ -0,0 +1,66 @@
+/**
+ * Copyright (c) 2026 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdio.h>
+
+#include "pico/stdlib.h"
+#include "pico/async_context_threadsafe_background.h"
+#include "pico/test.h"
+
+PICOTEST_MODULE_NAME("pico_async_context_test", "pico_async_context_test test harness");
+
+static void at_time_worker_fn(async_context_t *context, async_at_time_worker_t *worker) {
+    worker->user_data = (void*)true;
+}
+static async_at_time_worker_t at_time_worker = { .do_work = at_time_worker_fn };
+
+static void pending_worker_fn(async_context_t *async_context, async_when_pending_worker_t *worker) {
+    worker->user_data = (void*)true;
+    async_context_remove_at_time_worker(async_context, &at_time_worker); // remove at time worker
+}
+static async_when_pending_worker_t pending_worker = { .do_work = pending_worker_fn };
+
+static int issue_2836_test(void) {
+
+    async_context_threadsafe_background_t async_context;
+
+    // Set everything up
+    hard_assert(async_context_threadsafe_background_init_with_defaults(&async_context));
+    async_context_add_when_pending_worker(&async_context.core, &pending_worker);
+
+    // set an "at time" worker to run a long time in the future
+    hard_assert(!at_time_worker.user_data);
+    async_context_add_at_time_worker_at(&async_context.core, &at_time_worker, make_timeout_time_ms(100)); // .1s
+
+    // run a "pending" now, this will remove the "at time" worker we just setup above
+    hard_assert(!pending_worker.user_data);
+    async_context_set_work_pending(&async_context.core, &pending_worker);
+    busy_wait_us_32(500); // Pending worker should run pretty quickly
+    hard_assert(pending_worker.user_data);
+    hard_assert(!at_time_worker.user_data);
+
+    // Setup the "at time" worker again in .1s
+    async_context_add_at_time_worker_at(&async_context.core, &at_time_worker, make_timeout_time_ms(100)); // .1s
+
+    // Wait long enough that the "at time" worker to happen
+    busy_wait_us_32(200000); // .2s
+    if (!at_time_worker.user_data) { // this should be set by the "at time" worker, it's a bug if it doesn't!
+        panic("test fail: async at time worker did not run");
+    }
+    return 0;
+}
+
+int main() {
+    setup_default_uart();
+
+    PICOTEST_START();
+
+    PICOTEST_START_SECTION("Issue #2836 defect - async at time worker problem");
+    issue_2836_test();
+    PICOTEST_END_SECTION();
+
+    PICOTEST_END_TEST();
+}

tools/bazel_build.py

@@ -47,6 +47,7 @@ BUILD_CONFIGURATIONS = (
                 "//test/pico_sha256_test:pico_sha256_test",
                 "//test/pico_stdio_test:pico_stdio_test",
                 "//test/pico_time_test:pico_time_test",
+                "//test/pico_async_context_test:pico_async_context_test",
 
                 # Pretty much only Picotool and pioasm build on Windows.
                 "//..." if os.name == "nt" else "",