Add dummy map in fixtures

recaf-core/src/testFixtures/java/software/coley/recaf/test/dummy/DummyEmptyMap.java

@@ -0,0 +1,69 @@
+package software.coley.recaf.test.dummy;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Set;
+
+public class DummyEmptyMap<K, V> implements Map<K, V> {
+
+	@Override
+	public int size() {
+		return 0;
+	}
+
+	@Override
+	public boolean isEmpty() {
+		return true;
+	}
+
+	@Override
+	public boolean containsKey(Object key) {
+		return false;
+	}
+
+	@Override
+	public boolean containsValue(Object value) {
+		return false;
+	}
+
+	@Override
+	public V get(Object key) {
+		return null;
+	}
+
+	@Override
+	public V put(K key, V value) {
+		return null;
+	}
+
+	@Override
+	public V remove(Object key) {
+		return null;
+	}
+
+	@Override
+	public void putAll(Map<? extends K, ? extends V> m) {
+		// no-op
+	}
+
+	@Override
+	public void clear() {
+		// no-op
+	}
+
+	@Override
+	public Set<K> keySet() {
+		return Collections.emptySet();
+	}
+
+	@Override
+	public Collection<V> values() {
+		return Collections.emptySet();
+	}
+
+	@Override
+	public Set<Entry<K, V>> entrySet() {
+		return Collections.emptySet();
+	}
+}