Add a test for --sparse (#45).

Makefile.am

@@ -95,6 +95,7 @@ tests/Modifiers_-_--line-mode.test \
 tests/Modifiers_-_--size_from_file_size.test \
 tests/Modifiers_-_--size.test \
 tests/Modifiers_-_--sync.test \
+tests/Sparse_-_Basic.test \
 tests/Terminal_-_Detect_width.test \
 tests/Transfer_-_--rate-limit.test \
 tests/Transfer_-_--remote.test \

tests/Sparse_-_Basic.test

@@ -0,0 +1,89 @@
+#!/bin/sh
+#
+# Transfer a large chunk of data through pv using pipes, sending it in a
+# bursty fashion, and make sure some of it consists of blocks of null bytes. 
+# Check data correctness afterwards, and if dd can produce a sparse file,
+# check that pv's output is also sparse.
+
+# Allow all tests to be skipped, e.g. during a release build
+test "${SKIP_ALL_TESTS}" = "1" && exit 77
+
+true "${testSubject:?not set - call this from 'make check'}"
+true "${workFile1:?not set - call this from 'make check'}"
+true "${workFile2:?not set - call this from 'make check'}"
+true "${workFile3:?not set - call this from 'make check'}"
+
+# generate some data, with a hole in the middle.
+dd if=/dev/urandom of="${workFile1}" bs=4096 count=640 2>/dev/null
+dd if=/dev/null of="${workFile1}" bs=4096 count=0 seek=1280 2>/dev/null
+dd if=/dev/urandom of="${workFile1}" bs=4096 count=1280 seek=1280 2>/dev/null
+
+# check that sparse files are supported.
+cat < "${workFile1}" > "${workFile3}"
+inputBlocks="$(ls -1s "${workFile1}" | awk '{print $1}')"
+nonSparseBlocks="$(ls -1s "${workFile3}" | awk '{print $1}')"
+if test "${inputBlocks}" -eq "${nonSparseBlocks}"; then
+	echo 'sparse files not supported'
+	exit 77
+fi
+
+inputChecksum=$(cksum "${workFile1}" | awk '{print $1}')
+
+# read through pv and test afterwards
+(
+dd if="${workFile1}" bs=1 count=9000
+sleep 1
+dd if="${workFile1}" bs=1 skip=9000 count=1240
+sleep 1
+dd if="${workFile1}" bs=1024 skip=10 count=1014
+sleep 1
+dd if="${workFile1}" bs=1024 skip=1024 count=1024
+sleep 1
+dd if="${workFile1}" bs=1024 skip=2048
+) 2>/dev/null | "${testSubject}" -q -O -L 2M | cat > "${workFile2}"
+
+outputChecksum=$(cksum "${workFile2}" | awk '{print $1}')
+
+if ! test "${inputChecksum}" = "${outputChecksum}"; then
+	echo "checksum mismatch with dd | pv | cat"
+	exit 1
+fi
+
+# same again but with one less pipe
+(
+dd if="${workFile1}" bs=1 count=9000
+sleep 1
+dd if="${workFile1}" bs=1 skip=9000 count=1240
+sleep 1
+dd if="${workFile1}" bs=1024 skip=10 count=1014
+sleep 1
+dd if="${workFile1}" bs=1024 skip=1024 count=1024
+sleep 1
+dd if="${workFile1}" bs=1024 skip=2048
+) 2>/dev/null | "${testSubject}" -q -O -L 2M > "${workFile2}"
+
+outputChecksum=$(cksum "${workFile2}" | awk '{print $1}')
+
+if ! test "${inputChecksum}" = "${outputChecksum}"; then
+	echo "checksum mismatch with dd | pv > file"
+	exit 1
+fi
+
+outputBlocks="$(ls -1s "${workFile2}" | awk '{print $1}')"
+
+# Note that we only check that the output has any holes at all (and that the
+# input had holes).  We don't compare pv's output with dd's output directly,
+# because the exact number of holes might differ intermittently.
+
+if test "${nonSparseBlocks}" -gt "${inputBlocks}" && ! test "${outputBlocks}" -lt "${nonSparseBlocks}"; then
+	echo "output is not sparse"
+	echo "input file:"
+	ls -ls "${workFile1}"
+	echo "output file:"
+	ls -ls "${workFile2}"
+	echo "input file without holes:"
+	ls -ls "${workFile3}"
+	exit 1
+fi
+
+exit 0