* Factory for [calls][Call], which can be used to send HTTP requests and read their responses.
 *
 * ## OkHttpClients Should Be Shared
 *
 * OkHttp performs best when you create a single `OkHttpClient` instance and reuse it for all of
 * your HTTP calls. This is because each client holds its own connection pool and thread pools.
 * Reusing connections and threads reduces latency and saves memory. Conversely, creating a client

    val call3 = client.newCall(Request(server.url("/")))
    call3.execute().use { response ->
      assertThat(
        response.body.string(),
      ).isEqualTo("c")
    }

    // All calls share a connection.
    assertThat(server.takeRequest().sequenceNumber).isEqualTo(0)
    assertThat(server.takeRequest().sequenceNumber).isEqualTo(1)
    assertThat(server.takeRequest().sequenceNumber).isEqualTo(2)

      snapshot1.assertValue(0, "a")
      assertThat(readFileOrNull(getCleanFile("k1", 0))).isEqualTo(afterRemoveFileContents)
      assertThat(readFileOrNull(getDirtyFile("k1", 0))).isNull()

      // On all platforms files are deleted when all sources are closed.
      snapshot1.assertValue(1, "a")
      assertThat(readFileOrNull(getCleanFile("k1", 0))).isNull()
      assertThat(readFileOrNull(getDirtyFile("k1", 0))).isNull()
    }
  }

    expected: String?,
    source: Source?,
  ) {
    val actual = source!!.buffer().readUtf8()
    assertThat(actual).isEqualTo(expected)
  }

  /**
   * Returns true when all work currently in progress by the watchdog have completed. This method
   * creates more work for the watchdog and waits for that work to be executed. When it is, we know
   * work that preceded this call is complete.
   */