在mockito中使用apacheflink和scala。尝试在模拟数据流中注入一个字符串来测试两个测试用例。我不知道如何用一些数据来模拟flink的datastream对象。有什么想法吗？

import org.apache.commons.lang3.StringUtils
import org.apache.flink.streaming.api.scala.DataStream
import org.scalatest.FunSuite
import org.scalatest.mockito.MockitoSugar

class MockTest extends FunSuite with MockitoSugar {

  test ("Test DataStream with valid string") {
    var mockDataStream = mock[DataStream[String]]
    // inject "hello" to this datastream

    filterOutBlanks(mockDataStream)

    // verify mockDataStream is not empty
  }

  test ("Test DataStream with empty string") {
    var mockDataStream = mock[DataStream[String]]
    // inject "  " to this datastream

    filterOutBlank(mockDataStream)

    // verify mockDataStream is empty
  }

  def filterOutBlank(source: DataStream[String]): DataStream[String] = {
    source.filter(x => {
      StringUtils.isNotBlank(x)
    })
  }

}