feat(mock): add onceReturnValue mock method

mock/fn.ts

@@ -59,7 +59,19 @@ function fn(
   const onceImplementation = (
     implementation: (...args: unknown[]) => unknown,
   ): MockObject => {
-    mockFnStore["onceImplementations"].unshift(implementation);
+    mockFnStore["onceImplementations"].push(implementation);
+    return call as MockObject;
+  };
+
+  /** Sets a mock function what return specific value to be called only once.
+   * This takes precedence over the default mock function.
+   * Follow the FIFO.
+   *
+   * @param value
+   * @returns
+   */
+  const onceReturnValue = (value: unknown): MockObject => {
+    mockFnStore["onceImplementations"].push(() => value);
     return call as MockObject;
   };
 
@@ -81,6 +93,7 @@ function fn(
     defaultImplementation,
     defaultReturnValue,
     onceImplementation,
+    onceReturnValue,
   }).reduce(
     (acc, [key, value]) => ({
       ...acc,

mock/fn_test.ts

@@ -90,6 +90,12 @@ Deno.test("onceImplementation should call only one time", () => {
   assertEquals(onceImplementation.mock.calls.length, 1);
   mockObject();
   assertEquals(onceImplementation.mock.calls.length, 1);
+
+  const mock = fn().onceImplementation(() => 1).onceImplementation(() => 2);
+
+  assertEquals(mock(), 1);
+  assertEquals(mock(), 2);
+  assertEquals(mock(), undefined);
 });
 
 Deno.test("onceImplementation should be called in preference to default implementation", () => {
@@ -162,8 +168,22 @@ Deno.test("defaultReturnValue", () => {
   const mockObject = fn();
   mockObject.defaultImplementation(() => 2).defaultReturnValue(1);
 
-  mockObject();
+  mockObject(1, 2, 3);
 
-  assertEquals(mockObject.mock.calls, [[]]);
+  assertEquals(mockObject.mock.calls, [[1, 2, 3]]);
   assertEquals(mockObject.mock.results, [{ type: "return", value: 1 }]);
 });
+
+Deno.test("onceReturnValue", () => {
+  assertExists(fn().onceReturnValue);
+  assertEquals(fn().onceReturnValue(1)(), 1);
+
+  const mockObject = fn();
+
+  mockObject.onceReturnValue(1).onceReturnValue(2).onceImplementation(() => 3);
+
+  assertEquals(mockObject(), 1);
+  assertEquals(mockObject(), 2);
+  assertEquals(mockObject(), 3);
+  assertEquals(mockObject(), undefined);
+});

mock/mock.ts

@@ -42,6 +42,7 @@ interface MockObject<A extends readonly unknown[] = any[], R = unknown> {
   onceImplementation(
     implementation: (...args: A) => R,
   ): MockObject<A, R>;
+  onceReturnValue(value: R): MockObject<A, R>;
 }
 
 /** mock result store */