Add more tests

tests/Modifiers_-_--force.sh

@@ -0,0 +1,36 @@
+#!/bin/sh
+#
+# Check that the progress bar is produced when "--force" is used, and is not
+# when it is not, providing stderr is a file.
+
+# Dummy assignments for "shellcheck".
+testSubject="${testSubject:-false}"; workFile1="${workFile1:-.tmp1}";
+
+dd if=/dev/zero bs=100 count=1 2>/dev/null \
+| "${testSubject}" -f -p -i 0.1 -L 100 >/dev/null 2>"${workFile1}"
+
+# There should be more than 2 different lines of output.
+#
+lineCount=$(tr '\r' '\n' < "${workFile1}" | sort | uniq -u | wc -l | tr -dc '0-9')
+if ! test "${lineCount}" -gt 2; then
+	echo "fewer than 3 different progress lines with \"--force\" (${lineCount})"
+	tr '\r' '\n' < "${workFile1}" | sort | uniq -u
+	exit 1
+fi
+
+# Now try again without "--force".
+
+dd if=/dev/zero bs=100 count=1 2>/dev/null \
+| "${testSubject}" -p -i 0.1 -L 100 >/dev/null 2>"${workFile1}"
+
+# There should be no output without "--force".
+#
+if test -s "${workFile1}"; then
+	echo "unexpected output when not using \"--force\""
+	tr '\r' '\n' < "${workFile1}" | sort | uniq -u
+	exit 1
+fi
+
+exit 0
+
+# EOF