This property describes the cost of a test. When parallel testing is enabled, tests in the test set will be run in descending order of cost. Projects can explicitly define the cost of a test by setting this property to a floating point value.

When the cost of a test is not defined by the project, ctest will initially use a default cost of 0. It computes a weighted average of the cost each time a test is run and uses that as an improved estimate of the cost for the next run. The more a test is re-run in the same build directory, the more representative the cost should become.