test: sleep for a second before running docgen

Sponsored-by: author

1 files changed, 15 insertions, 0 deletions

diff --git a/check b/check
index c0f26fb..1220ad8 100755
--- a/check
+++ b/check
@@ -4,6 +4,7 @@ import argparse
 import glob
 import os
 import sys
+import time
 
 from subprocess import PIPE, DEVNULL, STDOUT
 
@@ -121,6 +122,20 @@ class Runcmd:
 
     def docgen(self, md, output, **kwargs):
         """Run the Subplot document generator"""
+
+        # GitLab CI, and other CI engines, runs tests under Docker, which uses
+        # an overlay file system, which at least sometimes only has full-second
+        # time stamps in file meta data, and sometimes that seems to happen
+        # when the kernel needs to flush its inode cache, and so it's not very
+        # deterministic. This leads to occasional test failures. To prevent
+        # such flaky tests, we wait for a second to make sure the time stamp of
+        # the output will be newer than the input has.
+        #
+        # This is an ugly kluge. It would be possible to check if the sleep is
+        # needed, but that kind of code is going to be tricky. Best avoid
+        # tricky code in test suites. Test code should be obviously correct.
+        time.sleep(1)
+
         self.cargo(
             [
                 "run",