test/py: Implement pytest infrastructure

This tool aims to test U-Boot by executing U-Boot shell commands using the
console interface. A single top-level script exists to execute or attach
to the U-Boot console, run the entire script of tests against it, and
summarize the results. Advantages of this approach are:

- Testing is performed in the same way a user or script would interact
  with U-Boot; there can be no disconnect.
- There is no need to write or embed test-related code into U-Boot itself.
  It is asserted that writing test-related code in Python is simpler and
  more flexible that writing it all in C.
- It is reasonably simple to interact with U-Boot in this way.

A few simple tests are provided as examples. Soon, we should convert as
many as possible of the other tests in test/* and test/cmd_ut.c too.

The hook scripts, relay control utilities, and udev rules I use for my
own HW setup are published at https://github.com/swarren/uboot-test-hooks.

See README.md for more details!

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Tested-by: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org> #v3

test/py/u_boot_spawn.py

@@ -0,0 +1,174 @@
+# Copyright (c) 2015-2016, NVIDIA CORPORATION. All rights reserved.
+#
+# SPDX-License-Identifier: GPL-2.0
+
+# Logic to spawn a sub-process and interact with its stdio.
+
+import os
+import re
+import pty
+import signal
+import select
+import time
+
+class Timeout(Exception):
+    '''An exception sub-class that indicates that a timeout occurred.'''
+    pass
+
+class Spawn(object):
+    '''Represents the stdio of a freshly created sub-process. Commands may be
+    sent to the process, and responses waited for.
+    '''
+
+    def __init__(self, args):
+        '''Spawn (fork/exec) the sub-process.
+
+        Args:
+            args: array of processs arguments. argv[0] is the command to execute.
+
+        Returns:
+            Nothing.
+        '''
+
+        self.waited = False
+        self.buf = ''
+        self.logfile_read = None
+        self.before = ''
+        self.after = ''
+        self.timeout = None
+
+        (self.pid, self.fd) = pty.fork()
+        if self.pid == 0:
+            try:
+                # For some reason, SIGHUP is set to SIG_IGN at this point when
+                # run under "go" (www.go.cd). Perhaps this happens under any
+                # background (non-interactive) system?
+                signal.signal(signal.SIGHUP, signal.SIG_DFL)
+                os.execvp(args[0], args)
+            except:
+                print 'CHILD EXECEPTION:'
+                import traceback
+                traceback.print_exc()
+            finally:
+                os._exit(255)
+
+        self.poll = select.poll()
+        self.poll.register(self.fd, select.POLLIN | select.POLLPRI | select.POLLERR | select.POLLHUP | select.POLLNVAL)
+
+    def kill(self, sig):
+        '''Send unix signal "sig" to the child process.
+
+        Args:
+            sig: The signal number to send.
+
+        Returns:
+            Nothing.
+        '''
+
+        os.kill(self.pid, sig)
+
+    def isalive(self):
+        '''Determine whether the child process is still running.
+
+        Args:
+            None.
+
+        Returns:
+            Boolean indicating whether process is alive.
+        '''
+
+        if self.waited:
+            return False
+
+        w = os.waitpid(self.pid, os.WNOHANG)
+        if w[0] == 0:
+            return True
+
+        self.waited = True
+        return False
+
+    def send(self, data):
+        '''Send data to the sub-process's stdin.
+
+        Args:
+            data: The data to send to the process.
+
+        Returns:
+            Nothing.
+        '''
+
+        os.write(self.fd, data)
+
+    def expect(self, patterns):
+        '''Wait for the sub-process to emit specific data.
+
+        This function waits for the process to emit one pattern from the
+        supplied list of patterns, or for a timeout to occur.
+
+        Args:
+            patterns: A list of strings or regex objects that we expect to
+                see in the sub-process' stdout.
+
+        Returns:
+            The index within the patterns array of the pattern the process
+            emitted.
+
+        Notable exceptions:
+            Timeout, if the process did not emit any of the patterns within
+            the expected time.
+        '''
+
+        for pi in xrange(len(patterns)):
+            if type(patterns[pi]) == type(''):
+                patterns[pi] = re.compile(patterns[pi])
+
+        try:
+            while True:
+                earliest_m = None
+                earliest_pi = None
+                for pi in xrange(len(patterns)):
+                    pattern = patterns[pi]
+                    m = pattern.search(self.buf)
+                    if not m:
+                        continue
+                    if earliest_m and m.start() > earliest_m.start():
+                        continue
+                    earliest_m = m
+                    earliest_pi = pi
+                if earliest_m:
+                    pos = earliest_m.start()
+                    posafter = earliest_m.end() + 1
+                    self.before = self.buf[:pos]
+                    self.after = self.buf[pos:posafter]
+                    self.buf = self.buf[posafter:]
+                    return earliest_pi
+                events = self.poll.poll(self.timeout)
+                if not events:
+                    raise Timeout()
+                c = os.read(self.fd, 1024)
+                if not c:
+                    raise EOFError()
+                if self.logfile_read:
+                    self.logfile_read.write(c)
+                self.buf += c
+        finally:
+            if self.logfile_read:
+                self.logfile_read.flush()
+
+    def close(self):
+        '''Close the stdio connection to the sub-process.
+
+        This also waits a reasonable time for the sub-process to stop running.
+
+        Args:
+            None.
+
+        Returns:
+            Nothing.
+        '''
+
+        os.close(self.fd)
+        for i in xrange(100):
+            if not self.isalive():
+                break
+            time.sleep(0.1)