Allow checking variable state in tests, use it in iterations.ccl, explain in example.ccl

tests/data/example.ccl

@@ -4,6 +4,7 @@ After the --- line comes the first test -- the operator string, followed by an e
 If the first operator line is "position=XXX", position is parsed as an int and that is used as the current position in the sentence for this and any following tests. Default position is 0.
 Tests are separated from one another by a --- line.
 This test loads no sentence, but can change the position anyway. Tagset is kipi by default.
+Variable state can be checked by a name=value lines after the expected output.
 tagset=ikipi
 ---
 equal(["aaa"], "aaa")
@@ -13,3 +14,10 @@ True
 lower(["A"])
 
 ["a"]
+---
+setvar($b:A, setvar($t:B, subst))
+
+True
+A=True
+B={subst}
+

tests/data/iterations.ccl

 tagset=kipi
+sentence=t01.xml
 ---
 rlook(begin, end, $Test, True)
 
 True
 ---
+llook(0, end, $V, False)
+
+False
+V=nowhere

tests/datadriven.cpp

@@ -98,7 +98,24 @@ void test_one_item_actual(const compare_test& c)
 			expected_output = "";
 			operator_string = "";
 			++line_no;
-			std::getline(ifs_in, line);
+			while (ifs_in.good() && line != "---" && line != "") {
+				std::getline(ifs_in, line);
+				std::vector<std::string> fields;
+				boost::algorithm::split(fields, line, boost::is_any_of(separators));
+				if (fields.size() == 2) {
+					boost::shared_ptr<Wccl::Value> v;
+					v = fu.variables()->get<Wccl::Value>(fields[0]);
+					if (!v) {
+						BOOST_ERROR("Invalid variable name in test: "
+							<< fields[0] << " on line " << line_no);
+					} else if (v->to_string(tagset) != fields[1]) {
+						BOOST_ERROR("Variable " << fields[0]
+							<< "value mismatch on line "
+							<< line_no << "\n: expected " << fields[1]
+							<< " got " << v->to_string(tagset));
+					}
+				}
+			}
 			BOOST_REQUIRE(line == "---" || line == "");
 		} else {
 			if (operator_string.empty() && line.substr(0, 9) == "position=") {