Big data is a collection of large data-sets that cannot be processed using traditional computing techniques.
The first step of big data testing also referred as pre-Hadoop stage involves process validation. Data from various source like RDBMS, weblogs, social media, etc. should be validated to make sure that correct data is pulled into system
The second step is a validation of "MapReduce". In this stage, the tester verifies the business logic validation on every node and then validating them after running against multiple nodes, ensuring that the Map Reduce process works correctly.
The final or third stage of Big Data testing is the output validation process. The output data files are generated and ready to be moved to an EDW (Enterprise Data Warehouse) or any other system based on the requirement.