ddt

Devious Database Testing

A library to make Database testing a little easier. It currently comprises:

• A DDT Fixture to intercept calls to a database and insert test values without the need for a database.
• Prepared Statement Spy - this will wrap a prepared statement instance and spy on the setter calls, to allow you to retrieve the SQL with the parameters pre-formatted within the original SQL.

DDTFixture

The problem is that code of the form:

  final Connection connection = DriverManager.getConnection("connection details");
  final PreparedStatement preparedStatement = connection.prepareStatement("select column_1, column_2, column_3 from some_table");
  final ResultSet rs = preparedStatement.executeQuery();
  while(rs.next()){
    final String columnOne = rs.getString(1);
    final int columnTwo = rs.getInt(2);
    final double columnThree = rs.getDouble(3);
  }

Cannot be tested without database setup and tear down scripts, and are unlikely to be run outside of a CI environment (which may also become a little brittle to setup without some investment in automation).

DDTFixture allows you to specify (with minimal boilerplate) values that should be iterated when a class under test calls through to the database using DriverManager.

There is an end-to-end example in info.bowkett.ddt.examples.DDTFixtureUsage But at the bare minimum you specify:

   @RunWith(PowerMockRunner.class)
   @PrepareForTest(DDTFixtureUsage.SomeClassThatReferencesDriverManager.class)

At the top of your unit test. Then at the start of your test case:

   final Connection connection = mock(Connection.class);
   PowerMockito.mockStatic(DriverManager.class);
   when(DriverManager.getConnection(anyString())).thenReturn(connection);
   ddtFixture = DDTFixture.forPreparedStatement(connection);

Then before your class under test queries the database/constructs its Statement/PreparedStatement/CallableStatement (all 3 are supported), use the following code:

   final Row row1 = new Row("A String", 3.1411d, 42);
   final Row row2 = new Row("String",   3.141d,  42);
   ddtFixture.setResultSet(row1, row2);

PreparedStatementSpy

The intent is to allow access to the SQL and params (in many implementations these are often obscured by the driver) such that the SQL could just be taken and run against the database. This class will add some overhead at runtime due to storing the parameters, so you may only wish to use it when an exception is thrown, see example code:

final Connection connection = DriverManager.getConnection("some.url");
final PreparedStatement pstmt = connection.prepareStatement(getSql());
try{
  // decorateStatement is some method of yours that sets the SQL params on the PreparedStatement
  decorateStatement(pstmt);
 }
 catch(SQLException e){
   System.err.println("Cannot execute SQL:");
   final PreparedStatement stmtSpy = new PreparedStatementSpy(pstmt, getSql());
   decorateStatement(stmtSpy);
   System.err.println("Problematic SQL:"+stmtSpy);
 }