test: test useAccessor hook

src/hooks/useAccessor.ts

@@ -12,9 +12,13 @@ export function useAccessor<R>(
         ref.current = value;
     }, []);
 
-    if (value) setValue(value);
-    return [
-        getValue,
-        React.useMemo(() => (value ? undefined : setValue), [setValue, value]),
-    ];
+    // If a value was initially provided then no setter is returned
+    const maybeSetValue = React.useMemo(function getSetValue() {
+        return value === undefined ? setValue : undefined;
+        // eslint-disable-next-line react-hooks/exhaustive-deps
+    }, []);
+    // If a value was initially provided then keep the ref updated
+    if (!maybeSetValue) setValue(value);
+
+    return [getValue, maybeSetValue];
 }

tests/hooks.test.ts

@@ -1,8 +1,36 @@
 import { act, renderHook } from "@testing-library/react-hooks";
 import { useDispatch } from "src";
 import { createContextWithValue } from "src/createContext";
+import { useAccessor } from "src/hooks/useAccessor";
 import { useObservable } from "src/hooks/useObservable";
 
+describe("useAccessor", () => {
+    const renderAccessorHook = <V>(initialValue?: V) =>
+        renderHook((value = initialValue) => useAccessor(value));
+
+    it("returns a getter and setter if no initial value provided", () => {
+        const { result, rerender } = renderAccessorHook();
+        const [getter, setter] = result.current;
+        expect(getter()).toBeUndefined();
+        expect(setter).toBeDefined();
+        setter?.("some value");
+        expect(getter()).toBe("some value");
+        rerender("other value");
+        expect(getter()).toBe("some value");
+    });
+
+    it("returns a getter only if an initial value is provided", () => {
+        const { result, rerender } = renderAccessorHook("initial value");
+        const [getter, setter] = result.current;
+        expect(getter()).toBe("initial value");
+        expect(setter).toBeUndefined();
+        setter?.("some value");
+        expect(getter()).toBe("initial value");
+        rerender("other value");
+        expect(getter()).toBe("other value");
+    });
+});
+
 describe("useDispatch", () => {
     const mockValue = {
         dispatch: async (a: Action<string, string>) => a,