diff --git a/packages/core/test/utils.test.ts b/packages/core/test/utils.test.ts
new file mode 100644
index 0000000000..a822f8851d
--- /dev/null
+++ b/packages/core/test/utils.test.ts
@@ -0,0 +1,88 @@
+import { assertExhaustive, tryCatch, promiseWithResolvers } from "../src/utils.js";
+
+describe("assertExhaustive", () => {
+  it("should throw an error when called", () => {
+    expect(() => assertExhaustive("unexpected" as never)).toThrow(Error);
+  });
+});
+
+describe("tryCatch", () => {
+  it("should resolve with [null, value] when promise resolves", async () => {
+    const promise = Promise.resolve(42);
+    const result = await tryCatch(promise);
+    expect(result).toEqual([null, 42]);
+  });
+
+  it("should resolve with [error, null] when promise rejects", async () => {
+    const error = new Error("fail");
+    const promise = Promise.reject(error);
+    const result = await tryCatch(promise);
+    expect(result[0]).toBe(error);
+    expect(result[1]).toBeNull();
+  });
+
+  it("should resolve with [error, null] when promise throws non-Error", async () => {
+    const promise = Promise.reject("fail");
+    const result = await tryCatch(promise);
+    expect(result[0]).toBe("fail");
+    expect(result[1]).toBeNull();
+  });
+
+  it("should resolve with [null, undefined] when promise resolves to undefined", async () => {
+    const promise = Promise.resolve(undefined);
+    const result = await tryCatch(promise);
+    expect(result).toEqual([null, undefined]);
+  });
+
+  it("should resolve with [null, value] when promise is already resolved", async () => {
+    const resolved = Promise.resolve("done");
+    const result = await tryCatch(resolved);
+    expect(result).toEqual([null, "done"]);
+  });
+
+  it("should resolve with [null, undefined] when promise is undefined", async () => {
+    const result = await tryCatch(undefined);
+    expect(result).toEqual([null, undefined]);
+  });
+});
+
+describe("promiseWithResolvers", () => {
+  it("should return a deferred promise with resolve and reject", async () => {
+    const deferred = promiseWithResolvers<number>();
+    expect(typeof deferred.promise.then).toBe("function");
+    expect(typeof deferred.resolve).toBe("function");
+    expect(typeof deferred.reject).toBe("function");
+    let resolved = false;
+    deferred.promise.then((value: number) => {
+      expect(value).toBe(123);
+      resolved = true;
+    });
+    deferred.resolve(123);
+    await deferred.promise;
+    expect(resolved).toBe(true);
+  });
+
+  it("should reject the promise when reject is called", async () => {
+    const deferred = promiseWithResolvers<string>();
+    const error = new Error("fail");
+    let caught: Error | null = null;
+    deferred.promise.catch((e: Error) => {
+      caught = e;
+    });
+    deferred.reject(error);
+    await expect(deferred.promise).rejects.toBe(error);
+    expect(caught).toBe(error);
+  });
+
+  it("should allow resolving with undefined", async () => {
+    const deferred = promiseWithResolvers<void>();
+    let resolved = false;
+    deferred.promise.then((value: void) => {
+      expect(value).toBeUndefined();
+      resolved = true;
+    });
+    deferred.resolve();
+    await deferred.promise;
+    expect(resolved).toBe(true);
+  });
+});