Test filters context map & message builder (#4886)

mocks/include/mocks/Channel.hpp

@@ -0,0 +1,16 @@
+#pragma once
+
+#include "common/Channel.hpp"
+
+namespace chatterino::mock {
+
+class MockChannel : public Channel
+{
+public:
+    MockChannel(const QString &name)
+        : Channel(name, Channel::Type::Twitch)
+    {
+    }
+};
+
+}  // namespace chatterino::mock