How to Mock "DriverManager.getConnection"

[Christian Schneider]

Hi,

I need to test an existing class that gets a connection by calling the static method DriverManager.getConnection(...).

Any ideas how to mock that?

Example Class:

public class Query implements Runnable {

private final String statement;

private Connection connection;

// ...

@Override

public void run() {

Statement jdbcStatement = null;

try {

this.connection = DriverManager.getConnection("jdbc:hive2://" + this.hiveHost + ":" + this.hivePort + "/default", "hive", "");

jdbcStatement = this.connection.createStatement();

final boolean resultSetAvailable = jdbcStatement.execute(constructStatementWithKey());

if (resultSetAvailable)  {

this.resultSet = jdbcStatement.getResultSet();

// ...

}

else {

closeQuery();

}

}

catch (final SQLException e) {

// ...

}

// ...

}

}

Example Test:

public class QueryTest {

Query cut =  new Query(null, null, "1", "SELECT * FROM foo", 1);

@Before

public void setup()

{

// somehow inject a mock for DriverManager.getConnection(.*);

}

@Test

public void shouldRunWithoutException() throws SQLException

{

this.query.run();

}

}

Best Regards,

Christian.

[Eric Lefevre-Ardant]

You need to wrap your static method and get it called from a class that is instantiable, or some equivalent solution.

There have been a few discussions on this on the mailing list. See

  https://groups.google.com/forum/#!topic/mockito/RtF57_7pAsQ

or

  https://groups.google.com/forum/#!topicsearchin/mockito/static/mockito/1Z1p6LrXpb0 (your problem is similar to mocking the call to a constructor).

Apparently, there are other mock-related projects that can mock static methods (PowerMockito, maybe ?), but from what I remember they are much to cumbersome to use.

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[KARR, DAVID]

As another responder indicated, you either have to change your CUT (class under test) to accommodate this, or you have to use PowerMockito.  Here’s some documentation: http://code.google.com/p/powermock/wiki/MockitoUsage13.  It’s definitely more complicated than plain Mockito, but mocking a single static method is about as simple as it gets.  It can get quite a bit more complicated.  Generally, when you have to use PowerMock, it indicates a design problem in your CUT, implying that you’ve given it multiple (too many) responsibilities.  For instance, if you have code that directly accesses a database, put only the direct database access code into a DAO class, with very little conditional logic, and put the logic that depends on what you get from the database (or decides what to put there), in a separate class.

 

If you’re going to do this, however, A basic outline of what’s required is this:

 

@RunWith(PowerMockRunner.class)

@PrepareForTest(DriverManager.class) // Need this for any classes with static methods that need to be mocked.

public class MyClass {

...

    <method signature> {

        ...

        Connection connection = mock(Connection.class);

        PowerMockito.mockStatic(DriverManager.class);

        PowerMockito.when(DriverManager.getConnection(anyString(), anyString(), anyString()).thenReturn(connection);

 

 

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