* the `@Rule` annotation:
 *
 * ```java
 * @Rule public final MockWebServerRule serverRule = new MockWebServerRule();
 * ```
 *
 * For Kotlin the `@JvmField` annotation is also necessary:
 *
 * ```kotlin
 * @JvmField @Rule val serverRule = MockWebServerRule()
 * ```
 */
class MockWebServerRule : ExternalResource() {
  val server: MockWebServer = MockWebServer()

  override fun before() {

```
@Rule public final MockWebServerRule serverRule = new MockWebServerRule();
```

The `serverRule` field has a `server` field. It is an instance of `MockWebServer`. That instance
will be shut down automatically after the test runs.

For Kotlin, the `@JvmField` annotation is also necessary:

```
@JvmField @Rule val serverRule = MockWebServerRule()

       <version>1.6.0</version>
     </dependency>
     ```

 *  New: `Cache.initialize()`. Call this on a background thread to eagerly
    initialize the response cache.
 *  New: Fold `MockWebServerRule` into `MockWebServer`. This makes it easier to
    write JUnit tests with `MockWebServer`. The `MockWebServer` library now
    depends on JUnit, though it continues to work with all testing frameworks.