Add tests for CashShopSurpriseHandler

src/test/java/testutil/HandlerTest.java

@@ -0,0 +1,24 @@
+package testutil;
+
+import client.Character;
+import client.Client;
+import org.junit.jupiter.api.BeforeEach;
+import org.mockito.Mock;
+
+import static org.mockito.Mockito.lenient;
+
+public abstract class HandlerTest {
+    protected static final int ACCOUNT_ID = 1702;
+
+    @Mock
+    protected Client client;
+
+    @Mock
+    protected Character chr;
+
+    @BeforeEach
+    void prepareClient() {
+        lenient().when(client.getAccID()).thenReturn(ACCOUNT_ID);
+        lenient().when(client.getPlayer()).thenReturn(chr);
+    }
+}