Restructure tests and adjust display format, to better understand what each test is testing.

tests/Modifiers_-_--interval.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+#
+# Check that the update interval can be set.
+
+sleep 1 | "${testSubject}" -f -i 0.1 >/dev/null 2>"${workFile1}"
+
+# There should be more than 6 lines of output.
+#
+NUM=$(tr '\r' '\n' < "${workFile1}" | wc -l | tr -d ' ')
+test $NUM -gt 6
+
+# EOF