With fast fallback, OkHttp attempts to connect to multiple web servers concurrently. It keeps whichever route connects first and cancels all of the others. Its rules are:

 * Prefer to alternate IP addresses from different address families, (IPv6 / IPv4), starting with IPv6.

}

@AfterClass
public static void afterClass() {
    runner.close();
    runner.clean();
}
```

### Testing Best Practices

- Minimize `Thread.sleep()` - use only when absolutely necessary
- For timestamp tests: use minimal delays (50-100ms)
- Clean only test-specific indices (not `_all` unless needed)
- Use `runner.refresh()` after index operations

            try {
                // Wait before retry (except first attempt)
                if (attempt > 0) {
                    long delay = retryDelay * (1L << attempt); // Exponential backoff
                    Thread.sleep(delay);
                    log.debug("Reconnection attempt {} for {}", attempt + 1, info.getPath());
                }

                // Perform the actual reconnection

    assertThat(server.takeRequest().exchangeIndex).isEqualTo(0)

    // Give the socket a chance to become stale.
    connection!!.idleAtNs -= IDLE_CONNECTION_HEALTHY_NS
    Thread.sleep(250)

    val requestB =
      Request(
        url = server.url("/"),
        body = "b".toRequestBody("text/plain".toMediaType()),
      )
    val responseB = client.newCall(requestB).execute()

        entry.setMaxAge(100); // 100ms

        assertFalse(entry.isExpired());
        assertFalse(entry.needsRefresh());

        // Wait for expiration
        try {
            Thread.sleep(150);
        } catch (InterruptedException e) {
            // Ignore
        }

        assertTrue(entry.isExpired());
        assertTrue(entry.needsRefresh());
    }

    @Test

    }
  }

  @Test
  fun fullCallTimeoutDoesNotApplyOnceConnected() {
    enableProtocol(Protocol.HTTP_2)
    val body =
      MockSocketHandler()
        .sendResponse("response A\n")
        .sleep(750, TimeUnit.MILLISECONDS)
        .sendResponse("response B\n")
        .receiveRequest("request C\n")
        .exhaustResponse()
        .exhaustRequest()
    server.enqueue(
      MockResponse

for HTTPS:

```java
HeldCertificate localhostCertificate = new HeldCertificate.Builder()
    .addSubjectAlternativeName("localhost")
    .build();
```

[`HandshakeCertificates`][handshake_certificates] keeps the certificates for a TLS handshake.
Use its [builder][handshake_certificates_builder] to define which certificates the HTTPS server
returns to its clients. The returned instance can create an `SSLSocketFactory` that implements this

        // Some number of tests will report here, but not fail due to this delay.
        println("Delaying to avoid flakes")
        Thread.sleep(500L)
        println("After delay: " + connectionPool.connectionCount())
      }

      connectionPool.evictAll()
      assertEquals(0, connectionPool.connectionCount()) {

    assertThat(recordedRequest.url.encodedQuery).isEqualTo(
      "ct&dns=AAABAAABAAAAAAAABmdvb2dsZQNjb20AAAEAAQ",
    )

    assertThat(cacheEvents()).containsExactly(CacheMiss::class)

    Thread.sleep(2000)
    server.enqueue(
      dnsResponse(
        "0000818000010003000000000567726170680866616365626f6f6b03636f6d0000010001c00c000500010" +

    override fun contentType(): MediaType? = null

    override fun writeTo(sink: BufferedSink) {
      for (i in 0 until 50) {
        sink.writeUtf8("abc")
        sink.flush()
        Thread.sleep(100)
      }
      fail("")
    }
  }