diff --git a/tests/output_checker.py b/tests/output_checker.py
new file mode 100644
index 0000000..50d40bc
--- /dev/null
+++ b/tests/output_checker.py
@@ -0,0 +1,148 @@
+#! /usr/bin/env python3
+# Copyright © 2020, RedHat Inc.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library. If not, see <http://www.gnu.org/licenses/>.
+# Authors:
+#       Benjamin Berg <bberg@redhat.com>
+
+import os
+import sys
+import fcntl
+import io
+import re
+import time
+import threading
+
+class OutputChecker(object):
+
+    def __init__(self, out=sys.stdout):
+        self._output = out
+        self._pipe_fd_r, self._pipe_fd_w = os.pipe()
+        self._partial_buf = b''
+        self._lines_sem = threading.Semaphore()
+        self._lines = []
+        self._reader_io = io.StringIO()
+
+        # Just to be sure, shouldn't be a problem even if we didn't set it
+        fcntl.fcntl(self._pipe_fd_r, fcntl.F_SETFL,
+                    fcntl.fcntl(self._pipe_fd_r, fcntl.F_GETFL) | os.O_CLOEXEC)
+        fcntl.fcntl(self._pipe_fd_w, fcntl.F_SETFL,
+                    fcntl.fcntl(self._pipe_fd_w, fcntl.F_GETFL) | os.O_CLOEXEC)
+
+        # Start copier thread
+        self._thread = threading.Thread(target=self._copy)
+        self._thread.start()
+
+    def _copy(self):
+        while True:
+            r = os.read(self._pipe_fd_r, 1024)
+            if not r:
+                return
+
+            l = r.split(b'\n')
+            l[0] = self._partial_buf + l[0]
+            self._lines.extend(l[:-1])
+            self._partial_buf = l[-1]
+
+            self._lines_sem.release()
+
+            os.write(self._output.fileno(), r)
+
+    def check_line_re(self, needle_re, timeout=0, failmsg=None):
+        deadline = time.time() + timeout
+
+        if isinstance(needle_re, str):
+            needle_re = needle_re.encode('ascii')
+
+        r = re.compile(needle_re)
+        ret = []
+
+        while True:
+            try:
+                l = self._lines.pop(0)
+            except IndexError:
+                # Check if should wake up
+                if not self._lines_sem.acquire(timeout = deadline - time.time()):
+                    if failmsg:
+                        raise AssertionError(failmsg)
+                    else:
+                        raise AssertionError('Timed out waiting for needle %s (timeout: %0.2f)' % (str(needle_re), timeout))
+                continue
+
+            ret.append(l)
+            if r.search(l):
+                return ret
+
+    def check_line(self, needle, timeout=0, failmsg=None):
+        if isinstance(needle, str):
+            needle = needle.encode('ascii')
+
+        needle_re = re.escape(needle)
+
+        return self.check_line_re(needle_re, timeout=timeout, failmsg=failmsg)
+
+    def check_no_line_re(self, needle_re, wait=0, failmsg=None):
+        deadline = time.time() + wait
+
+        if isinstance(needle_re, str):
+            needle_re = needle_re.encode('ascii')
+
+        r = re.compile(needle_re)
+        ret = []
+
+        while True:
+            try:
+                l = self._lines.pop(0)
+            except IndexError:
+                # Check if should wake up
+                if not self._lines_sem.acquire(timeout = deadline - time.time()):
+                    # Timed out, so everything is good
+                    break
+                continue
+
+            ret.append(l)
+            if r.search(l):
+                if failmsg:
+                    raise AssertionError(failmsg)
+                else:
+                    raise AssertionError('Found needle %s but shouldn\'t have been there (timeout: %0.2f)' % (str(needle_re), timeout))
+
+        return ret
+
+    def check_no_line(self, needle, wait=0, failmsg=None):
+        if isinstance(needle, str):
+            needle = needle.encode('ascii')
+
+        needle_re = re.escape(needle)
+
+        return self.check_no_line_re(needle_re, wait=wait, failmsg=failmsg)
+
+    def clear(self):
+        ret = self._lines
+        self._lines = []
+        return ret
+
+    def assert_closed(self, timeout=1):
+        self._thread.join(timeout)
+        if self._thread.is_alive() != False:
+            raise AssertionError("OutputCheck: Write side has not been closed yet!")
+
+    @property
+    def fd(self):
+        return self._pipe_fd_w
+
+    def writer_attached(self):
+        os.close(self._pipe_fd_w)
+        self._pipe_fd_w = -1
+