chore: remove Singleton & replace getIApp with getApp (#5514)

mocks/include/mocks/BaseApplication.hpp

@@ -0,0 +1,37 @@
+#pragma once
+
+#include "mocks/DisabledStreamerMode.hpp"
+#include "mocks/EmptyApplication.hpp"
+#include "singletons/Settings.hpp"
+
+#include <QString>
+
+namespace chatterino::mock {
+
+/**
+ * BaseApplication intends to be a mock application with a few more sane defaults, but with less configurability
+ */
+class BaseApplication : public EmptyApplication
+{
+public:
+    BaseApplication()
+        : settings(this->settingsDir.filePath("settings.json"))
+    {
+    }
+
+    explicit BaseApplication(const QString &settingsData)
+        : EmptyApplication(settingsData)
+        , settings(this->settingsDir.filePath("settings.json"))
+    {
+    }
+
+    IStreamerMode *getStreamerMode() override
+    {
+        return &this->streamerMode;
+    }
+
+    Settings settings;
+    DisabledStreamerMode streamerMode;
+};
+
+}  // namespace chatterino::mock

mocks/include/mocks/EmptyApplication.hpp

@@ -17,7 +17,17 @@ public:
     {
     }
 
-    virtual ~EmptyApplication() = default;
+    explicit EmptyApplication(const QString &settingsData)
+        : EmptyApplication()
+    {
+        QFile settingsFile(this->settingsDir.filePath("settings.json"));
+        settingsFile.open(QIODevice::WriteOnly | QIODevice::Text);
+        settingsFile.write(settingsData.toUtf8());
+        settingsFile.flush();
+        settingsFile.close();
+    }
+
+    ~EmptyApplication() override = default;
 
     bool isTest() const override
     {
@@ -249,7 +259,6 @@ public:
         return nullptr;
     }
 
-protected:
     QTemporaryDir settingsDir;
     Paths paths_;
     Args args_;