tests: make tests requiring a delay to pass, more robust

* tests/init.cfg: Introduce a retry_delay_() function to
repeatedly call a test function that requires a delay.
This delay can now be shorter for the common case on fast
systems, but will double until a configurable limit it reached
before failing on slower systems.
* tests/dd/reblock: Use retry_delay_.
* tests/misc/cat-buf: Likewise.
* tests/misc/stdbuf: Likewise.
* tests/tail-2/F-vs-rename: Likewise.
* tests/tail-2/flush-initial: Likewise.
* tests/tail-2/tail-n0f: Likewise.
* tests/tail-2/wait: Likewise.
* test/dd/misc: Comment that delay is needed to trigger failure.

1 files changed, 25 insertions, 25 deletions

diff --git a/tests/tail-2/F-vs-rename b/tests/tail-2/F-vs-rename
index 38a1b3f40..74db80137 100755
--- a/tests/tail-2/F-vs-rename
+++ b/tests/tail-2/F-vs-rename
@@ -42,36 +42,36 @@ mv a b || fail=1
 until grep inaccessible out >/dev/null 2>&1; do :; done
 
 echo x > a
-# Wait up to 4s for this to appear in the output:
+# Wait up to 6.3s for this to appear in the output:
 # "tail: `...' has appeared;  following end of new file"
-found=false
-for i in $(seq 20); do
-  grep 'has appeared;' out > /dev/null && { found=true; break; }
-  sleep .2
-done
-$found || { echo "$0: a: unexpected delay?"; cat out; fail=1; }
+tail_f_vs_rename_1()
+{
+  local delay="$1"
+  grep 'has appeared;' out > /dev/null ||
+    { sleep $delay; return 1; }
+}
+retry_delay_ tail_f_vs_rename_1 .1 7 ||
+  { echo "$0: a: unexpected delay?"; cat out; fail=1; }
 
 echo y >> b
-# Wait up to 4s for "y" to appear in the output:
-found=false
-for i in $(seq 20); do
-  case $(tr '\n' @ < out) in
-    *'@@==> b <==@y@') found=true; break 2;;
-  esac
-  sleep .2
-done
-$found || { echo "$0: b: unexpected delay?"; cat out; fail=1; }
+# Wait up to 6.3s for "y" to appear in the output:
+tail_f_vs_rename_2() {
+  local delay="$1"
+  tr '\n' @ < out | grep '@@==> b <==@y@$' > /dev/null ||
+    { sleep $delay; return 1; }
+}
+retry_delay_ tail_f_vs_rename_2 .1 7 ||
+  { echo "$0: b: unexpected delay?"; cat out; fail=1; }
 
 echo z >> a
-# Wait up to 4s for "z" to appear in the output:
-found=false
-for i in $(seq 20); do
-  case $(tr '\n' @ < out) in
-    *'@@==> a <==@z@') found=true; break 2;;
-  esac
-  sleep .2
-done
-$found || { echo "$0: b: unexpected delay?"; cat out; fail=1; }
+# Wait up to 6.3s for "z" to appear in the output:
+tail_f_vs_rename_3() {
+  local delay="$1"
+  tr '\n' @ < out | grep '@@==> a <==@z@$' > /dev/null ||
+    { sleep $delay; return 1; }
+}
+retry_delay_ tail_f_vs_rename_3 .1 7 ||
+  { echo "$0: a: unexpected delay?"; cat out; fail=1; }
 
 kill -HUP $pid