java - How to mock jdbc connection and resultSet using Mockito in TestNG -

i have write unit tests have problem mocking resultset , jdbc connection.

i have method:

@test public void test3() throws sqlexception, ioexception {      connection jdbcconnection = mockito.mock(connection.class);     resultset resultset = mockito.mock(resultset.class);      mockito.when(resultset.next()).thenreturn(true).thenreturn(true).thenreturn(true).thenreturn(false);     mockito.when(resultset.getstring(1)).thenreturn("table_r3").thenreturn("table_r1").thenreturn("table_r2");     mockito.when(jdbcconnection             .createstatement()             .executequery("select name tables"))             .thenreturn(resultset);      //when     list<string> nameoftableslist = null;     try {         nameoftableslist = helper.gettablesname(jdbcconnection);     } catch (sqlexception e) {         // todo auto-generated catch block         e.printstacktrace();     }      //then     assert.assertequals(nameoftableslist.size(), 3); } 

and error showing in line executequery("select name tables") , sounds this:

java.lang.nullpointerexception helpertest.test3(helpertest.java:71) 

any ideas whats going wrong?

you need create expectation on jdbcconnection.createstatement().

by default, believe null returned.

should read like:

resultset resultset = mockito.mock(resultset.class); mockito.when(resultset.next()).thenreturn(true).thenreturn(true).thenreturn(true).thenreturn(false); mockito.when(resultset.getstring(1)).thenreturn("table_r3").thenreturn("table_r1").thenreturn("table_r2");  statement statement = mockito.mock(statement.class); mockito.when(statement.executequery("select name tables")).thenreturn(resultset);  connection jdbcconnection = mockito.mock(connection.class); mockito.when(jdbcconnection.createstatement()).thenreturn(statement);