Module: Mutineer::ChildStdout

Defined in:
lib/mutineer/child_stdout.rb

Overview

Silences stdout in a forked child that runs tests. Every fork boundary calls ChildStdout.silence once, right after fork, so the test runners themselves do not touch stdout. The parent reads each child's result from a separate pipe or from the exit status, never from stdout.

Stderr stays open: it carries mutineer's own diagnostics from the child.

Stdlib-only, so the app-side daemon can load it.

Class Method Summary collapse

Class Method Details

.silence ⇒ void

This method returns an undefined value.

Points fd 1 at File::NULL and makes $stdout the real STDOUT again.

The reopen goes through STDOUT, not $stdout: the parent may have left $stdout as a StringIO, which cannot reopen. A test that calls $stdout.reopen (Minitest's capture_subprocess_io, RSpec's to_stdout_from_any_process) then gets a real IO. Child processes of the test inherit the silenced fd 1 too.

The reopen takes an open IO, not a path. A path reopen checks the access mode of STDOUT and raises ArgumentError when a parent left STDOUT on a file in another mode (for example the "w+x" Tempfile of Minitest's capture_subprocess_io).

Call it only in a child that exits after the tests run. Nothing restores the previous stdout.



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# File 'lib/mutineer/child_stdout.rb', line 30

def self.silence
  File.open(File::NULL, "w") { |null| STDOUT.reopen(null) }
  $stdout = STDOUT
end