[Libguestfs] [nbdkit PATCH] tests: Check that cache-min-block-size works properly

[Martin Kletzander]

Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
---
 tests/test-cache-block-size.sh | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/tests/test-cache-block-size.sh b/tests/test-cache-block-size.sh
index d20cc94002b6..5e83ebc1cfaa 100755
--- a/tests/test-cache-block-size.sh
+++ b/tests/test-cache-block-size.sh
@@ -47,24 +47,35 @@ truncate -s 128K cache-block-size.img
 
 # Run nbdkit with the caching filter.
 start_nbdkit -P cache-block-size.pid -U $sock --filter=cache \
-             file cache-block-size.img cache-min-block-size=4K
+             file cache-block-size.img cache-min-block-size=64K \
+             cache-on-read=true
 
 nbdsh --connect "nbd+unix://?socket=$sock" \
       -c '
-# Write some pattern data to the overlay and check it reads back OK.
-buf = b"abcd" * 16384
-h.pwrite(buf, 32768)
+# Read half of cache-min-block-size
+
 zero = h.pread(32768, 0)
 assert zero == bytearray(32768)
-buf2 = h.pread(65536, 32768)
-assert buf == buf2
 
-# Flushing should write through to the underlying file.
-h.flush()
+buf = b"abcd" * 8192
 
+# Write past the first read
+with open("cache-block-size.img", "wb") as file:
+    file.seek(32768)
+    file.write(buf * 2)
+    file.truncate(131072)
+
+# Check that it got written
 with open("cache-block-size.img", "rb") as file:
-    zero = file.read(32768)
-    assert zero == bytearray(32768)
+    file.seek(32768)
     buf2 = file.read(65536)
-    assert buf == buf2
+    assert (buf * 2) == buf2
+
+# Now read the rest of the cache-min-block-size, it should stay empty
+zero = h.pread(32768, 32768)
+assert zero == bytearray(32768)
+
+# Read past that, the pattern should be visible there
+buf2 = h.pread(32768, 65536)
+assert buf == buf2
 '
-- 
2.32.0