Smoke test proves that "the pipes will not leak, the keys seal properly, the circuit will not burn, or the software will not crash outright” the system is ready for more robust testing.
Smoke testing is preliminary testing to reveal simple failures severe enough to reject a prospective software release. In this case, the smoke is metaphorical. A subset of test cases that cover the most important functionality of a component or system are selected and run, to ascertain if the most crucial functions of a program work correctly.
Below are the flowcharts depecting few important smoke tests covered in an SAP BW testing projects before starting with actual system test: