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_console_sandbox.py

@@ -0,0 +1,79 @@
+# Copyright (c) 2015 Stephen Warren
+# Copyright (c) 2015-2016, NVIDIA CORPORATION. All rights reserved.
+#
+# SPDX-License-Identifier: GPL-2.0
+
+# Logic to interact with the sandbox port of U-Boot, running as a sub-process.
+
+import time
+from u_boot_spawn import Spawn
+from u_boot_console_base import ConsoleBase
+
+class ConsoleSandbox(ConsoleBase):
+    '''Represents a connection to a sandbox U-Boot console, executed as a sub-
+    process.'''
+
+    def __init__(self, log, config):
+        '''Initialize a U-Boot console connection.
+
+        Args:
+            log: A multiplexed_log.Logfile instance.
+            config: A "configuration" object as defined in conftest.py.
+
+        Returns:
+            Nothing.
+        '''
+
+        super(ConsoleSandbox, self).__init__(log, config, max_fifo_fill=1024)
+
+    def get_spawn(self):
+        '''Connect to a fresh U-Boot instance.
+
+        A new sandbox process is created, so that U-Boot begins running from
+        scratch.
+
+        Args:
+            None.
+
+        Returns:
+            A u_boot_spawn.Spawn object that is attached to U-Boot.
+        '''
+
+        return Spawn([self.config.build_dir + '/u-boot'])
+
+    def kill(self, sig):
+        '''Send a specific Unix signal to the sandbox process.
+
+        Args:
+            sig: The Unix signal to send to the process.
+
+        Returns:
+            Nothing.
+        '''
+
+        self.ensure_spawned()
+        self.log.action('kill %d' % sig)
+        self.p.kill(sig)
+
+    def validate_exited(self):
+        '''Determine whether the sandbox process has exited.
+
+        If required, this function waits a reasonable time for the process to
+        exit.
+
+        Args:
+            None.
+
+        Returns:
+            Boolean indicating whether the process has exited.
+        '''
+
+        p = self.p
+        self.p = None
+        for i in xrange(100):
+            ret = not p.isalive()
+            if ret:
+                break
+            time.sleep(0.1)
+        p.close()
+        return ret