initial tests

tests/UI_button.cpp

@@ -0,0 +1,26 @@
+#include "Test.hpp"
+
+TEST(UI_button, to_from_json)
+{
+    UI_button button("button_id", "button_text", Color(255, 255, 255), Color(0, 0, 0), nullptr);
+    json j = button.to_json();
+    UI_button button2(j);
+    EXPECT_EQ(button.id(), button2.id());
+    EXPECT_EQ(button.text(), button2.text());
+    EXPECT_EQ(button.fg_color(), button2.fg_color());
+    EXPECT_EQ(button.bg_color(), button2.bg_color());
+
+    std::cout << j.dump(4) << std::endl;
+}
+
+void on_click(std::string id)
+{
+    UNUSED(id);
+    EXPECT_EQ(id, "button_id");
+}
+
+TEST(UI_button, on_click)
+{
+    UI_button button("button_id", "button_text", Color(255, 255, 255), Color(0, 0, 0), on_click);
+    button.click();
+}