doc/doc-txt/test-harness.txt

   1 EXIM'S BEHAVIOUR CHANGES WHEN RUNNING IN THE TEST HARNESS
   2 ---------------------------------------------------------
   3
   4 When Exim is running in its test harness, via the scripts in the exim-testsuite
   5 distribution, its behaviour is altered in a few ways, in order to make the
   6 regression testing work properly. The documentation for the test suite
   7 describes how a copy of the Exim binary is taken and patched in order to get it
   8 to run in the test harness. This document briefly lists the behavioural changes
   9 that result. They come into play when the Boolean variable running_in_test_
  10 harness is true.
  11
  12
  13 Privilege
  14 ---------
  15
  16 Exim does not give up its root privilege when called with -C or -D, nor does it
  17 insist on the caller being an admin user when starting a daemon, a queue
  18 runner, or requesting debug output.
  19
  20
  21 Small Pauses
  22 ------------
  23
  24 In a number of places, typically when a subprocess has been forked, there are
  25 short pauses of half or one second in one of the processes. This allows the
  26 other process to "go first"; it ensures that debugging or logging output always
  27 appears in the same order.
  28
  29
  30 Daemon
  31 ------
  32
  33 The daemon always writes a pid file when running in the test harness.
  34
  35
  36 CRAM-MD5
  37 --------
  38
  39 The cram_md5 authenticator always uses the same challenge string.
  40
  41
  42 Appendfile
  43 ----------
  44
  45 After a quota error, the "time since last read" for the file is forced to 10s,
  46 for repeatability.
  47
  48
  49 Memory management
  50 -----------------
  51
  52 Memory management debugging output contains only the store pool and the size
  53 (other information is too variable). New memory is initialized to contain F0 in
  54 all bytes.
  55
  56
  57 Queue running
  58 -------------
  59
  60 There's a facility (-Tqt) for fudging queue times for testing retry logic.
  61
  62
  63 Syslog
  64 ------
  65
  66 Exim never writes to syslog in the test harness. Attempts to do so are silently
  67 ignored. None of the tests actually specify syslog logging for any actual log
  68 lines, but there is one that tests the inability to open the main and panic
  69 logs, which by default then tries to write to syslog.
  70
  71
  72 SMTP connection timeout
  73 -----------------------
  74
  75 In order to be able to test timeout handling, a "connection refused" error is
  76 converted into a timeout if the timeout value is set to 999999s.
  77
  78
  79 Random numbers
  80 --------------
  81
  82 The seed for the pseudo-random number generator is set to a fixed value in the
  83 test harness, to ensure repeatability.
  84
  85
  86 Bounce messages
  87 ---------------
  88
  89 When Exim is submitting a bounce message to itself, unless the configuration
  90 has set queue_only, it uses -odi so that the bounce is delivered before the
  91 subprocess returns. This avoids a race that might put log lines in an arbitrary
  92 order.
  93
  94
  95 DNS lookups
  96 -----------
  97
  98 The real DNS resolver is never called. Instead, a fake resolver, which runs as
  99 a separate program, is used. It is part of the test suite and is documented
 100 there. This ensures complete control over the exact results of any DNS lookups.
 101
 102 An attempt to look up a PTR record for 99.99.99.99 or an IP address for a host
 103 whose name ends with .test.again.dns always yields a "try again" error.
 104
 105 A fake function is called instead of gethostbyname(). It recognizes the name
 106 "manyhome.test.ex" and generates a humungous number of IP addresses. It also
 107 recognizes an unqualified "localhost" and forces it to the appropriate loopback
 108 address (IPv4 or IPv6, as required). IP addresses are treated as literals. For
 109 other names, it does a DNS lookup (which of course actually calls the fake
 110 resolver) to find the host name.
 111
 112
 113 User names
 114 ----------
 115
 116 If unknown_login is set, it forces the login name, thus overriding the actual
 117 login for the test suite caller. When this happens, unknown_username provides a
 118 user name if it is set; otherwise an empty string is used.
 119
 120
 121 Ident
 122 -----
 123
 124 If -bh is used and both the sending host port and the incoming interface port
 125 are supplied, an ident (RFC 1413) call is made for testing purposes.
 126
 127
 128 Debug output
 129 ------------
 130
 131 Debugging output from the function that waits for the clock to tick at an
 132 appropriate resolution (before completing the arrival of a message, for
 133 example) is suppressed because the fractions of seconds that it contains will
 134 never be repeatable.
 135
 136
 137 Philip Hazel
 138 15 February 2006