fix potential test case failure

src/test/assertions.ts

@@ -1,22 +1,25 @@
 /** custom assertions that do a nicer job of type narrowing */
 
-import { Ok, Result, Error } from "../utils";
+import { Error, Ok, Result } from "../utils";
 
-export const assertOk = <T1, T2>(
+// note that using our preferred func-style actually changes behavior here for some reason and causes test failures (ts(2775))
+/* eslint-disable func-style */
+
+export function assertOk<T1, T2>(
   result: Result<T1, T2>
-): asserts result is Ok<T1, T2> => {
+): asserts result is Ok<T1, T2> {
   expect(result.isOk()).toEqual(true);
-};
+}
 
-export const assertError = <T1, T2>(
+export function assertError<T1, T2>(
   result: Result<T1, T2>
-): asserts result is Error<T1, T2> => {
+): asserts result is Error<T1, T2> {
   expect(result.isError()).toEqual(true);
-};
+}
 
-export const assertInstanceOf = <T1>(
+export function assertInstanceOf<T1>(
   value: unknown,
   type: T1
-): asserts value is T1 => {
+): asserts value is T1 {
   expect(value).toBeInstanceOf(type);
-};
+}