Qemu test case: wait dynamically until booted (#1330)

We have a test case, that performs full installations with with XFCE4
and Plasma Mobile. After each installation is through, we run
"pmbootstrap qemu" and connect to the VM via SSH to check for specific
running processes.

Before this commit, we assumed that the boot takes 90 seconds at most
and then the processes should exist. But sometimes the boot is faster
(so Travis waits just doing nothing) and sometimes it is slower (which
causes the test case to fail), all depending on the current workload
of the Travis CI servers. Now we try to find the processes we're
interested in each second for 3 minutes until we either succeed or
reach the time limit.

test/test_qemu_running_processes.py

@@ -31,7 +31,6 @@ import sys
 import shutil
 import shlex
 import time
-import logging
 
 # Import from parent directory
 pmb_src = os.path.realpath(os.path.join(os.path.dirname(__file__) + "/.."))
@@ -113,8 +112,6 @@ class Qemu(object):
         pmbootstrap_yes(args, config, ["install", "--no-fde"])
         self.process = pmbootstrap_run(args, config, ["qemu", "--display",
                                                       "none"], background=True)
-        logging.info("(test) wait 90s until the VM booted up")
-        time.sleep(90)
 
 
 @pytest.fixture
@@ -134,23 +131,44 @@ def ssh_run(args, command):
                                  "-o", "StrictHostKeyChecking=no",
                                  "-p", "2222", "testuser@localhost", "--",
                                  command],
-                          return_stdout=True)
+                          check=False, return_stdout=True)
     return ret
 
 
-def is_running(args, programs):
+def is_running(args, programs, tries=180, sleep_before_retry=1):
     """
     Simple check that looks for program names in the output of "ps ax".
     This is error-prone, only use it with programs that have a unique name.
+    With defaults retries and sleep_before_retry values, it will try each
+    second for 3 minutes.
+
+    :param programs: list of programs to check for, e.g. ["xfce4-desktop"]
+    :param tries: amount of tries with the wrong result before giving up
+    :param sleep_before_retry: time in seconds to sleep before trying again
     """
-    all = ssh_run(args, "ps ax")
-    ret = True
-    for program in programs:
-        if program in all:
+    print("Looking for programs to appear in the VM (tries: " + str(tries) +
+          "): " + ", ".join(programs))
+    for i in range(0, tries):
+        # Sleep
+        if i > 0:
+            time.sleep(sleep_before_retry)
+
+        # Get running programs via SSH
+        all = ssh_run(args, "ps ax")
+        if not all:
             continue
-        print(program + ": not found in 'ps ax'!")
-        ret = False
-    return ret
+
+        # Missing programs
+        missing = []
+        for program in programs:
+            if program not in all:
+                missing.append(program)
+        if not missing:
+            return True
+
+    # Not found
+    print("Programs not running: " + ", ".join(missing))
+    return False
 
 
 def test_xfce4(args, tmpdir, qemu):
@@ -159,7 +177,7 @@ def test_xfce4(args, tmpdir, qemu):
                              "Thunar", "dbus-daemon", "xfwm4"])
 
     # self-test of is_running()
-    assert is_running(args, ["invalid-process"]) is False
+    assert is_running(args, ["invalid-process"], 1) is False
 
 
 def test_plasma_mobile(args, tmpdir, qemu):