while (!source.exhausted()) {
          var rule: ByteString = source.readUtf8LineStrict().toRule() ?: continue

          if (rule.startsWith(EXCEPTION_RULE_MARKER)) {
            rule = rule.substring(1)
            // We use '\n' for end of value.
            totalExceptionRuleBytes += rule.size + 1
            sortedExceptionRules.add(rule)
          } else {
            totalRuleBytes += rule.size + 1 // We use '\n' for end of value.

Similarly, the reader thread must never block on writing because this can deadlock the connection. Consider a client and server that both violate this rule. If you get unlucky, they could fill up their TCP buffers (so that writes block) and then use their reader threads to write a frame. Nobody is reading on either end, and the buffers are never drained.

#### Do-stuff-later pool

```
@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()

 *
 * In Java JUnit 4 tests (ie. tests annotated `@org.junit.Test`), use this by defining a field with
 * 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()
 * ```
 */
@ExperimentalOkHttpApi

import org.junit.AssumptionViolatedException
import org.junit.Before
import org.junit.Ignore
import org.junit.Rule
import org.junit.Test

/**
 * Run with "./gradlew :android-test:connectedCheck -PandroidBuild=true" and make sure ANDROID_SDK_ROOT is set.
 */
class AndroidAsyncDnsTest {
  @JvmField @Rule
  val serverRule = MockWebServerRule()
  private lateinit var client: OkHttpClient

class MockWebServerRuleTest {
  @Test fun statementStartsAndStops() {
    val rule = MockWebServerRule()
    val called = AtomicBoolean()
    val statement: Statement =
      rule.apply(
        object : Statement() {
          override fun evaluate() {
            called.set(true)
            rule.server.url("/").toUrl().openConnection().connect()
          }
        },
        Description.EMPTY,
      )