In this episode Matthew and Federico discuss the differences between black box and white box testing. Based on their experience testing MVC and WebMatrix, they talk about problems that can happen if testers are too focused on code inspections as well as advantages if used properly.

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Black box and white box testing.

• Definitions
  • Black box is testing performed without knowledge of the product code. White box (or glass box) is testing with the knowledge of the product code.
  • A black box tester becomes an expert of the relationship between the program and the world on which it runs.
  • A white box tester becomes an expert of the structure of the program and the internal representation and management of data.
  • White box testing can also be described as “inspection” and is one of the test activities that does not involve code executing by a computer.
• Problems with white box testing
  • Customer detachment: When a tester starts justifying customer expected behavior based on implementation knowledge.
  • Bias based on visual complexity: When a tester bases strategy solely on how hard or simple a piece of code looks.
  • Overwhelmed by complexity: When a tester spends too much time understanding every single piece of code instead of testing.
• Advantages of white box testing
  • Source of information to guide testing.
  • Helps to better understand interaction between modules.
  • Can help in locating assumptions not easily found by blind inputs.