Modern C++ Programming with Test-Driven Development

Assertions

Assertions turn a test into an automated test. In the absence of an assertion, Google Mock simply executes a block of code. If you want to verify that the block of code worked, you’d need to manually inspect the results (perhaps by step-debugging or printing the contents of some variables).

You don’t have time for manual verification. TDD generates automated unit tests, which self-verify (see ​Tests Come FIRST​), saving you from the risky and tedious work of visually inspecting results. There’s hardly anything more wasteful than manually bringing up the GUI for an application, time and time again, in order to verify something that a unit test could have verified automatically.

When your test framework runs an individual test, it executes ...