Improvements to code coverage:

More tests and test cases are added to bring up
the percentage of library code covered by tests.

test/http/reason.cpp

@@ -7,3 +7,23 @@
 
 // Test that header file is self-contained.
 #include <beast/http/reason.hpp>
+
+#include <beast/unit_test/suite.hpp>
+
+namespace beast {
+namespace http {
+
+class reason_test : public unit_test::suite
+{
+public:
+    void run() override
+    {
+        for(int i = 1; i <= 999; ++i)
+            expect(reason_string(i) != nullptr);
+    }
+};
+
+BEAST_DEFINE_TESTSUITE(reason,http,beast);
+
+} // http
+} // beast