QA: unit tests for file ext filters

This adds a unit test for the recent AddFileExtListToFilter
to demonstrate how to use it and the expected output.

The unit tests are a bit clunky, as the vararg approach cannot
work winth strings passed at runtime.

qa/common/CMakeLists.txt

@@ -37,10 +37,11 @@ set( common_srcs
     ../../common/observable.cpp
 
     test_color4d.cpp
+    test_format_units.cpp
     test_hotkey_store.cpp
     test_title_block.cpp
     test_utf8.cpp
-    test_format_units.cpp
+    test_wildcards_and_files_ext.cpp
 
     libeval/test_numeric_evaluator.cpp
 

qa/common/test_wildcards_and_files_ext.cpp

@@ -0,0 +1,98 @@
+/*
+ * This program source code file is part of KiCad, a free EDA CAD application.
+ *
+ * Copyright (C) 2018 KiCad Developers, see CHANGELOG.TXT for contributors.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, you may find one here:
+ * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+ * or you may search the http://www.gnu.org website for the version 2 license,
+ * or you may write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+ */
+
+#include <unit_test_utils/unit_test_utils.h>
+
+#include <wildcards_and_files_ext.h>
+
+
+BOOST_AUTO_TEST_SUITE( WildcardFileExt )
+
+
+/**
+ * Data used to construct a simple test of one or more extensions
+ * and get a filter string for WX dialogs out
+ */
+struct ExtWildcardFilterCase
+{
+    /// The list of exts handled
+    std::vector<std::string> m_exts;
+
+    /// Filter for case-insensitive environments
+    std::string m_filter_case_insenstive;
+
+    /// Filter for regex-capable environments (case insensitive filter in a
+    /// case-sensitive environment)
+    std::string m_re_filter;
+};
+
+const static std::vector<ExtWildcardFilterCase> ext_wildcard_cases = {
+    {
+            { "png" },
+            " ( *.png)|*.png",
+            " ( *.png)|*.[pP][nN][gG]",
+    },
+    {
+            { "png", "gif" },
+            " ( *.png *.gif)|*.png;*.gif",
+            " ( *.png *.gif)|*.[pP][nN][gG];*.[gG][iI][fF]",
+    },
+};
+
+
+static constexpr bool should_use_regex_filters()
+{
+#ifdef __WXGTK__
+    return true;
+#else
+    return false;
+#endif
+}
+
+
+/**
+ * Check correct handling of filter strings (as used by WX)
+ */
+BOOST_AUTO_TEST_CASE( SingleFilter )
+{
+    const auto&       c = ext_wildcard_cases[0];
+    const std::string exp_filter =
+            should_use_regex_filters() ? c.m_re_filter : c.m_filter_case_insenstive;
+
+    const auto resp = AddFileExtListToFilter( 1, "png" );
+
+    BOOST_CHECK_EQUAL( resp, exp_filter );
+}
+
+BOOST_AUTO_TEST_CASE( MultipleFilter )
+{
+    const auto&       c = ext_wildcard_cases[1];
+    const std::string exp_filter =
+            should_use_regex_filters() ? c.m_re_filter : c.m_filter_case_insenstive;
+
+    const auto resp = AddFileExtListToFilter( 2, "png", "gif" );
+
+    BOOST_CHECK_EQUAL( resp, exp_filter );
+}
+
+BOOST_AUTO_TEST_SUITE_END()