如何编写测试用例readFile方法（返回类型为void）

Question

I am new in writing test cases, Please help me for writing test case for below methods . Thanks in advance!!

public void readFile() throws IOException{
  linesProcessed = 0;
  FileInputStream fileInStream = new FileInputStream(filePath);
  DataInputStream dataInStream = new DataInputStream(fileInStream);
  BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(dataInStream));
  String strLine;

  fileData.clear();
  while(StringUtils.isNotBlank((strLine = bufferedReader.readLine()))) {
    ++linesProcessed;
    processLine(strLine);
  }
  bufferedReader.close();
  dataInStream.close();
  fileInStream.close();         
}

Answer 1

Many things to say here.

First of all, to answer your question. When a method doesn't return something, you can still can check whether some "other state" gets updated accordingly.

In your case, one meaningful point of observation could be that call

processLine(strLine);

In other words: you could see what that method is doing, and somehow verify that the other method was called as you would expect it.

Then: you actually wrote hard-to-test code. One reason for that is because this method starts its work on a string (that points to a file). Instead, you could pass a reader object to that method already. Then there wouldn't be a need to use PowerMock for example. You simply prepare a reader object that has known content, and then you can verify that actions follow that match that prepared content!

Beyond that, you should learn about try-with-resources, and you should also study more how to do IO. There is no point in closing all 3 streams. When you create a reader on some other stream, and you close the outer reader, that "base" stream gets closed automatically along the way.