Question

I am getting this message in unit test expected:<interface java.sql.Connection> but was:<class com.mysql.jdbc.JDBC4Connection>

from my code:

@Test
public void connectionTest() throws SQLException{
    Connection conn = ConnectionManager.createConnection();
    assertEquals(Connection.class, conn.getClass());
    conn.close();
}

My mock class for getting connection:

public class ConnectionManager {


    @SuppressWarnings("unused")
    public static Connection createConnection() throws SQLException {
        String url = "jdbc:mysql://localhost:3306/library";
        String name = "root";
        String password = "root";
        Connection connection = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            connection =  DriverManager.getConnection(url, name, password);
        } catch (ClassNotFoundException e) {
            if (connection != null){
                connection.close();
            }
            throw new SQLException(e);
        }
        return connection;
    }
}

What is wrong with my code?

Answer 1

Your assert is fundamentally wrong.

Connection.class is an interface.
conn.getClass() will return a concrete class that implements that interface.