Testing Stdin Stdout

I needed to test the input and output of a cli program I was writing.

I needed to capture what was happening in a goroutine safe way so I ended up with the struct below.

Anywhere that did logging was passed this struct as their io.Writer

It has a lock as testing with -race complained (rightly) at multiple routines trying to access at once. This would also help ensure that messages were output in full, without interference from other write calls E The only other concern was that as it was a buffered output, you need to call flush before getting a string of the output to compare.

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type StdIO struct {  
   in        bytes.Buffer  
   out       bytes.Buffer  
   inReader  *bufio.Reader  
   outWriter *bufio.Writer  
   rMutex    sync.Mutex  
   wMutex    sync.Mutex  
}  
  
func (s *StdIO) Flush() {  
   s.wMutex.Lock()  
   defer s.wMutex.Unlock()  
   s.outWriter.Flush()  
}  
  
func (s *StdIO) Read(p []byte) (n int, err error) {  
   s.rMutex.Lock()  
   defer s.rMutex.Unlock()  
   return s.inReader.Read(p)  
}  
  
func (s *StdIO) Write(p []byte) (n int, err error) {  
   s.wMutex.Lock()  
   defer s.wMutex.Unlock()  
   return s.outWriter.Write(p)  
}  
  
func NewStdIO() *StdIO {  
   s := &StdIO{  
      in:  bytes.Buffer{},  
      out: bytes.Buffer{},  
   }  
   s.inReader = bufio.NewReader(&s.in)  
   s.outWriter = bufio.NewWriter(&s.out)  
   return s  
}