Always write first your asserts.
--- /dev/null
+package org.craftedsw.feature;
+
+import static org.mockito.Mockito.verify;
+
+import org.junit.Test;
+
+public class AccountShould {
+
+       private TransactionRepository transactionRepository;
+
+       @Test public void
+       store_a_deposit_transaction() {
+               
+       
+               verify(transactionRepository).addDeposit(100);
+       }
+
+}
 
--- /dev/null
+package org.craftedsw.feature;
+
+public class TransactionRepository {
+
+       public void addDeposit(int amount) {
+               throw new UnsupportedOperationException();
+       }
+
+}