add unit test framework for pair, bond, angle styles from progguide branch

unittest/force-styles/yaml_writer.h

@@ -0,0 +1,43 @@
+/* -*- c++ -*- ----------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   http://lammps.sandia.gov, Sandia National Laboratories
+   Steve Plimpton, sjplimp@sandia.gov
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+#ifndef YAML_WRITER_H
+#define YAML_WRITER_H
+
+#include "yaml.h"
+#include <cstdio>
+#include <string>
+
+class YamlWriter {
+public:
+    YamlWriter(const char * outfile);
+    virtual ~YamlWriter();
+
+    // emitters
+    void emit(const std::string &key, const double value);
+    void emit(const std::string &key, const long value);
+    void emit(const std::string &key, const int value);
+    void emit(const std::string &key, const std::string &value);
+    void emit_block(const std::string &key, const std::string &value);
+
+private:
+    FILE *fp;
+    yaml_emitter_t emitter;
+    yaml_event_t   event;
+
+private:
+    YamlWriter() {};
+    YamlWriter(const YamlWriter &){};
+};
+
+#endif