diff --git a/tests/org/kde/kdeconnect/MockSharedPreference.java b/tests/org/kde/kdeconnect/MockSharedPreference.java
deleted file mode 100644
index 9a500618..00000000
--- a/tests/org/kde/kdeconnect/MockSharedPreference.java
+++ /dev/null
@@ -1,159 +0,0 @@
-package org.kde.kdeconnect;
-
-import android.content.SharedPreferences;
-
-import androidx.annotation.Nullable;
-
-import java.util.HashMap;
-import java.util.Map;
-import java.util.Set;
-
-
-/**
- * Mock implementation of shared preference, which just saves data in memory using map.
- *
- * It DOES NOT support transactions, changes are immediate
- *
- * From https://gist.github.com/amardeshbd/354173d00b988574ee5019c4ba0c8a0b
- */
-class MockSharedPreference implements SharedPreferences {
-
-    private final HashMap<String, Object> preferenceMap;
-    private final MockSharedPreferenceEditor preferenceEditor;
-
-    public MockSharedPreference() {
-        preferenceMap = new HashMap<>();
-        preferenceEditor = new MockSharedPreferenceEditor(preferenceMap);
-    }
-
-    @Override
-    public Map<String, ?> getAll() {
-        return preferenceMap;
-    }
-
-    @Nullable
-    @Override
-    public String getString(final String s, @Nullable final String def) {
-        if (!preferenceMap.containsKey(s)) return def;
-        return (String) preferenceMap.get(s);
-    }
-
-    @Nullable
-    @Override
-    public Set<String> getStringSet(final String s, @Nullable final Set<String> def) {
-        if (!preferenceMap.containsKey(s)) return def;
-        return (Set<String>) preferenceMap.get(s);
-    }
-
-    @Override
-    public int getInt(final String s, final int def) {
-        if (!preferenceMap.containsKey(s)) return def;
-        return (int) preferenceMap.get(s);
-    }
-
-    @Override
-    public long getLong(final String s, final long def) {
-        if (!preferenceMap.containsKey(s)) return def;
-        return (long) preferenceMap.get(s);
-    }
-
-    @Override
-    public float getFloat(final String s, final float def) {
-        if (!preferenceMap.containsKey(s)) return def;
-        return (float) preferenceMap.get(s);
-    }
-
-    @Override
-    public boolean getBoolean(final String s, final boolean def) {
-        if (!preferenceMap.containsKey(s)) return def;
-        return (boolean) preferenceMap.get(s);
-    }
-
-    @Override
-    public boolean contains(final String s) {
-        return preferenceMap.containsKey(s);
-    }
-
-    @Override
-    public Editor edit() {
-        return preferenceEditor;
-    }
-
-    @Override
-    public void registerOnSharedPreferenceChangeListener(final OnSharedPreferenceChangeListener onSharedPreferenceChangeListener) {
-
-    }
-
-    @Override
-    public void unregisterOnSharedPreferenceChangeListener(final OnSharedPreferenceChangeListener onSharedPreferenceChangeListener) {
-
-    }
-
-    static class MockSharedPreferenceEditor implements Editor {
-
-        private final HashMap<String, Object> preferenceMap;
-
-        MockSharedPreferenceEditor(final HashMap<String, Object> preferenceMap) {
-            this.preferenceMap = preferenceMap;
-        }
-
-        @Override
-        public Editor putString(final String s, @Nullable final String s1) {
-            preferenceMap.put(s, s1);
-            return this;
-        }
-
-        @Override
-        public Editor putStringSet(final String s, @Nullable final Set<String> set) {
-            preferenceMap.put(s, set);
-            return this;
-        }
-
-        @Override
-        public Editor putInt(final String s, final int i) {
-            preferenceMap.put(s, i);
-            return this;
-        }
-
-        @Override
-        public Editor putLong(final String s, final long l) {
-            preferenceMap.put(s, l);
-            return this;
-        }
-
-        @Override
-        public Editor putFloat(final String s, final float v) {
-            preferenceMap.put(s, v);
-            return this;
-        }
-
-        @Override
-        public Editor putBoolean(final String s, final boolean b) {
-            preferenceMap.put(s, b);
-            return this;
-        }
-
-        @Override
-        public Editor remove(final String s) {
-            preferenceMap.remove(s);
-            return this;
-        }
-
-        @Override
-        public Editor clear() {
-            preferenceMap.clear();
-            return this;
-        }
-
-        @Override
-        public boolean commit() {
-            return true;
-        }
-
-        @Override
-        public void apply() {
-            // Nothing to do, everything is saved in memory.
-        }
-    }
-
-}
diff --git a/tests/org/kde/kdeconnect/MockSharedPreference.kt b/tests/org/kde/kdeconnect/MockSharedPreference.kt
new file mode 100644
index 00000000..1559259c
--- /dev/null
+++ b/tests/org/kde/kdeconnect/MockSharedPreference.kt
@@ -0,0 +1,79 @@
+package org.kde.kdeconnect
+
+import android.content.SharedPreferences
+import android.content.SharedPreferences.OnSharedPreferenceChangeListener
+
+/**
+ * Mock implementation of shared preference, which just saves data in memory using map.
+ *
+ * It DOES NOT support transactions, changes are immediate
+ *
+ * From https://gist.github.com/amardeshbd/354173d00b988574ee5019c4ba0c8a0b
+ */
+internal class MockSharedPreference : SharedPreferences {
+    private val preferenceMap = mutableMapOf<String, Any?>()
+    private val preferenceEditor = MockSharedPreferenceEditor(preferenceMap)
+
+    override fun getAll(): Map<String, *> = preferenceMap
+    override fun getString(s: String, def: String?): String? = preferenceMap.getOrDefault(s, def) as String?
+    override fun getBoolean(s: String, def: Boolean): Boolean = preferenceMap.getOrDefault(s, def) as Boolean
+    override fun getInt(s: String, def: Int): Int = preferenceMap.getOrDefault(s, def) as Int
+    override fun getLong(s: String, def: Long): Long = preferenceMap.getOrDefault(s, def) as Long
+    override fun getFloat(s: String, def: Float): Float = preferenceMap.getOrDefault(s, def) as Float
+    override fun getStringSet(s: String, def: Set<String>?): Set<String>? = preferenceMap.getOrDefault(s, def) as Set<String>?
+    override fun contains(s: String): Boolean = preferenceMap.containsKey(s)
+    override fun edit(): SharedPreferences.Editor = preferenceEditor
+
+    override fun registerOnSharedPreferenceChangeListener(onSharedPreferenceChangeListener: OnSharedPreferenceChangeListener) {}
+    override fun unregisterOnSharedPreferenceChangeListener(onSharedPreferenceChangeListener: OnSharedPreferenceChangeListener) {}
+
+    internal class MockSharedPreferenceEditor(private val preferenceMap: MutableMap<String, Any?>) : SharedPreferences.Editor {
+        override fun putString(s: String, s1: String?): SharedPreferences.Editor {
+            preferenceMap[s] = s1
+            return this
+        }
+
+        override fun putStringSet(s: String, set: Set<String>?): SharedPreferences.Editor {
+            preferenceMap[s] = set
+            return this
+        }
+
+        override fun putInt(s: String, i: Int): SharedPreferences.Editor {
+            preferenceMap[s] = i
+            return this
+        }
+
+        override fun putLong(s: String, l: Long): SharedPreferences.Editor {
+            preferenceMap[s] = l
+            return this
+        }
+
+        override fun putFloat(s: String, v: Float): SharedPreferences.Editor {
+            preferenceMap[s] = v
+            return this
+        }
+
+        override fun putBoolean(s: String, b: Boolean): SharedPreferences.Editor {
+            preferenceMap[s] = b
+            return this
+        }
+
+        override fun remove(s: String): SharedPreferences.Editor {
+            preferenceMap.remove(s)
+            return this
+        }
+
+        override fun clear(): SharedPreferences.Editor {
+            preferenceMap.clear()
+            return this
+        }
+
+        override fun commit(): Boolean {
+            return true
+        }
+
+        override fun apply() {
+            // Nothing to do, everything is saved in memory.
+        }
+    }
+}