Add test for over-read when using stop-at-size (#166).

Makefile.am

@@ -99,6 +99,7 @@ tests/Terminal_-_Detect_width.test \
 tests/Transfer_-_--rate-limit.test \
 tests/Transfer_-_--remote.test \
 tests/Transfer_-_--stop-at-size.test \
+tests/Transfer_-_--stop-at-size_reads.test \
 tests/Watchfd_-_Multiple_descriptors.test \
 tests/Watchfd_-_Single_descriptor.test
 

tests/Transfer_-_--stop-at-size_reads.test

@@ -0,0 +1,54 @@
+#!/bin/sh
+#
+# Make sure -S stops reading at the given size.
+#
+# See https://codeberg.org/ivarch/pv/issues/166
+
+# 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'}"
+
+printf '%s\n' 'abcdefghi' | (
+"${testSubject}" -qSs5 > "${workFile1}"
+cat > "${workFile2}"
+)
+
+# pv should have read 5 bytes and put them into workFile1.
+pvOutput="$(cat "${workFile1}")"
+if ! test "${pvOutput}" = 'abcde'; then
+	echo "expected pv to write [abcde], got [${pvOutput}]"
+	exit 1
+fi
+
+# cat should have read the remaining bytes and put them into workFile2.
+catOutput="$(cat "${workFile2}")"
+if ! test "${catOutput}" = 'fghi'; then
+	echo "expected cat to write [fghi], got [${catOutput}]"
+	exit 1
+fi
+
+# Now repeat the test with -X to make sure there's no over-read there either.
+
+printf '%s\n' 'abcdefghi' | (
+"${testSubject}" -qXSs5 > "${workFile1}"
+cat > "${workFile2}"
+)
+
+# pv should have read 5 bytes and put nothing into workFile1.
+pvOutput="$(cat "${workFile1}")"
+if test -s "${workFile1}"; then
+	echo "with -X, expected pv to write nothing, got [${pvOutput}]"
+	exit 1
+fi
+
+# cat should have read the remaining bytes and put them into workFile2.
+catOutput="$(cat "${workFile2}")"
+if ! test "${catOutput}" = 'fghi'; then
+	echo "with pv -X, expected cat to write [fghi], got [${catOutput}]"
+	exit 1
+fi
+
+exit 0