Fix erroneous comments in rss_feed::set_rssurl

cppcheck pointed out that I overwrite variable's value right after
assigning it, and this proved to be true. However, while looking into
it, I found that the comments I left in the function don't match the
reality as the input that it gets are a bit different from the examples
in comments. It's sheer luck that the code that I got by making
a mistake turned out to be *right*.

So I removed superfluous code, amended the comments and added a few
tests to make sure I never step into that particular trap ever again.

src/rss.cpp

@@ -476,13 +476,10 @@ void rss_feed::set_rssurl(const std::string& u) {
 	if (rssurl_.substr(0,6) == "query:") {
 		/* Query string looks like this:
 		 *
-		 * "query:Title:unread = \"yes\" and age between 0:7" tag1 "tag two"
+		 * query:Title:unread = "yes" and age between 0:7
 		 *
-		 * At this point, we're only interested in the first part enclosed in
-		 * the quotes. Thus, we first tokenize using space as delimiter... */
-		std::vector<std::string> tokens = utils::tokenize_quoted(u, " ");
-		// and then further split by colon, so as to extract title and query
-		tokens = utils::tokenize_quoted(u, ":");
+		 * So we split by colons to get title and the query itself. */
+		std::vector<std::string> tokens = utils::tokenize_quoted(u, ":");
 
 		if (tokens.size() < 3) {
 			throw _s("too few arguments");

test/rss.cpp

@@ -2,6 +2,9 @@
 
 #include <rsspp.h>
 #include <rsspp_internal.h>
+#include <rss.h>
+#include <cache.h>
+#include <configcontainer.h>
 
 TEST_CASE("Throws exception if file doesn't exist", "[rsspp::parser]") {
 	rsspp::parser p;
@@ -227,3 +230,23 @@ TEST_CASE("W3C DTF to RFC 822 conversion behaves correctly with different "
 	}
 	tzset();
 }
+
+namespace newsbeuter {
+
+TEST_CASE("set_rssurl checks if query feed has a valid query", "[rss]") {
+	configcontainer cfg;
+	cache rsscache(":memory:", &cfg);
+	rss_feed f(&rsscache);
+
+	SECTION("invalid query results in exception") {
+		REQUIRE_THROWS(f.set_rssurl("query:a title:unread ="));
+		REQUIRE_THROWS(f.set_rssurl("query:a title:between 1:3"));
+	}
+
+	SECTION("valid query doesn't throw an exception") {
+		REQUIRE_NOTHROW(f.set_rssurl("query:a title:unread = \"yes\""));
+		REQUIRE_NOTHROW(f.set_rssurl("query:Title:unread = \"yes\" and age between 0:7"));
+	}
+}
+
+}