There are about 6 phases:

• Business and requirement understanding
• Test planning and estimation
• Designing test case and preparing test data
• Test execution with bug reporting and closure
• Summary report and result analysis
• Test closure

There are about 6 phases:
• Business and requirement understanding
• Test planning and estimation
• Designing test case and preparing test data
• Test execution with bug reporting and closure
• Summary report and result analysis
• Test closure

Here is the pictorial view:

ETL Testing

ETL Testing Process:
Although there are many ETL tools, there is a simple testing process which is commonly used in ETL testing. It is as important as the implementation of ETL tool into your business. Having a well defined ETL testing strategy can make the testing process much easier. Hence, this process need to be followed before you start the Data Integration processed with the selected ETL tool. In this ETL testing process, a group of experts comprising the programming and developing team will start writing SQL statements. The development team may customize according to the requirements.
ETL testing process is:
Analyzing the requirement – Understanding the business structure and their particular requirement.
Validation and Test Estimation – An estimation of time and expertise required to carry on with the procedure.
Test Planning and Designing the testing environment – Based on the inputs from the estimation, an ETL environment is planned and worked out.
Test Data preparation and Execution – Data for the test is prepared and executed as per the requirement.
Summary Report:  Upon the completion of the test run, a brief summary report is prepared for improvising and concluding.

It is a central component of a multi-dimensional model which contains the measures to be analyzed. Facts are related to dimensions.
Types of facts are:
• Additive Facts
• Semi-additive Facts
• Non-additive Facts

Cubes are data processing units comprised of fact tables and dimensions from the data warehouse.  It provides multi-dimensional analysis.

OLAP stands for Online Analytics Processing, and OLAP cube stores large data in multi-dimensional form for reporting purposes.

It consists of facts called as measures categorized by dimensions.

• Calculation Bug
• User Interface Bug
• Source Bugs
• Load condition bug
• ECP related bug
In addition to the above ETL testing questions, there may be other vital questions where you may be asked to mention the ETL tools which you have used earlier. Also, you might be asked about any debugging issues you have faced in your earlier experience or about any real time experience.