### Question:
AwsRdsInstanceView { public String getMasterUsername() { return databaseServer.getRootUserName(); } AwsRdsInstanceView(DatabaseServer databaseServer); Long getAllocatedStorage(); Integer getBackupRetentionPeriod(); String getDBInstanceClass(); String getDBInstanceIdentifier(); String getEngine(); String getEngineVersion(); String getMasterUsername(); String getMasterUserPassword(); String getMultiAZ(); String getStorageType(); List<String> getVPCSecurityGroups();  }### Answer:
@Test public void testMasterUsername() { when(server.getRootUserName()).thenReturn("root"); assertEquals("root", underTest.getMasterUsername()); }
@Test public void testNoMasterUsername() { when(server.getRootUserName()).thenReturn(null); assertNull(underTest.getMasterUsername()); }