Can a process read its own "standard out" stream?

Question

How would a process read its own output stream? I am writing automated tests which start a few application sub-processes (applications) in the same process as the test. Therefore, the standard out is a mix of test output and application output.

I want to read the output stream at runtime and fail the test if I see errors from the application. Is this possible/feasible? If so, how do I do it?

Note: I know I could start the applications as their own separate processes and then read their output streams. That's a lot of work from where I am now.

Also note, this is not a dupe of How to test a function's output (stdout/stderr) in Go unit tests, although that ticket is similar and helpful. The other ticket is about capturing output for a single function call. This ticket is about reading the entire stream, continuously. The correct answer is also a little different - it requires a pipe.

Answer 1

Yes, You may use os.Pipe() then process it yourself:

tmp := os.Stdout
r, w, err := os.Pipe()
if err != nil {
    panic(err)
}
os.Stdout = w

Or divert os.Stdout to a another file or strings.Builder.
Here is the detailed answer:
In Go, how do I capture stdout of a function into a string?