docs: polish expect api (#576)

Author: 9aoy

website/docs/en/api/test-api/expect.mdx

@@ -7,6 +7,28 @@ overviewHeaders: [2, 3]
 
 `expect` is used to assert values in tests. It provides a rich set of matchers, supports chainable modifiers, soft assertions, polling, and snapshot testing.
 
+You can import the `expect` API from the `@rstest/core` package:
+
+```ts
+import { expect, test } from '@rstest/core';
+
+test('should add two numbers correctly', () => {
+  expect(1 + 1).toBe(2);
+  expect(1 + 2).toBe(3);
+});
+```
+
+You can also get the `expect` API from the [test context](/api/test-api/test#testcontext), which is helpful for tracing assertion belonging in concurrent tests.
+
+```ts
+import { test } from '@rstest/core';
+
+test('should add two numbers correctly', ({ expect }) => {
+  expect(1 + 1).toBe(2);
+  expect(1 + 2).toBe(3);
+});
+```
+
 ## expect
 
 - **Type:** `<T>(actual: T, message?: string) => Assertion<T>`

website/docs/en/api/test-api/test.mdx

@@ -188,7 +188,9 @@ export interface TestContext {
   expect: Expect;
   /** The `onTestFinished` hook bound to the current test */
   onTestFinished: OnTestFinished;
+  /** The `onTestFailed` hook bound to the current test */
+  onTestFailed: OnTestFailed;
 }
 ```
 
-You can extend `TestContext` with custom fixtures using `test.extend`.
+You can also extend `TestContext` with custom fixtures using `test.extend`.

website/docs/zh/api/test-api/expect.mdx

@@ -7,6 +7,28 @@ overviewHeaders: [2, 3]
 
 `expect` 用于在测试中创建断言。Rstest 提供了丰富的 API 及匹配器，支持轮询、快照断言等。
 
+你可以从 `@rstest/core` 包中导入 `expect` API：
+
+```ts
+import { expect, test } from '@rstest/core';
+
+test('should add two numbers correctly', () => {
+  expect(1 + 1).toBe(2);
+  expect(1 + 2).toBe(3);
+});
+```
+
+你也可以从 [测试上下文](/api/test-api/test#testcontext) 中获取 `expect` API，这有助于在并行测试中准确追踪断言的来源。
+
+```ts
+import { test } from '@rstest/core';
+
+test('should add two numbers correctly', ({ expect }) => {
+  expect(1 + 1).toBe(2);
+  expect(1 + 2).toBe(3);
+});
+```
+
 ## expect
 
 - **类型：** `<T>(actual: T, message?: string) => Assertion<T>`

website/docs/zh/api/test-api/test.mdx

@@ -177,7 +177,9 @@ export interface TestContext {
   expect: Expect;
   /** The `onTestFinished` hook bound to the current test */
   onTestFinished: OnTestFinished;
+  /** The `onTestFailed` hook bound to the current test */
+  onTestFailed: OnTestFailed;
 }
 ```
 
-你可以通过 `test.extend` 方法通过自定义 fixture 的方式来扩展测试上下文。
+你也可以通过 `test.extend` 方法通过自定义 fixture 的方式来扩展测试上下文。