Mere moments ago, quoth I:
How do I tell in my jamfile when CI testing is occurring in order to disable the tests for CI builds.
I'm not familiar with Jamfiles (or CI, for that matter), so perhaps someone else should chime in at this point...
... but it does look like both Travis and Appveyor set the environment variable CI when building (they both set it to "true", but not with identical case; checking it against empty value is probably sufficient though), so you can possibly check that.
(They also set TRAVIS or APPVEYOR respectively, if you need to distinguish them.)
FWIW, Boost.Gil [1] and Boost.Phoenix [2] appears to have an example of changing compiler settings based on CI or not, which you could crib from. Most of the other libraries appear to do it differently -- they group the tests into different suites and their travis/appveyor files specify particular suites to run, or they have one test "outside" suites, with comments implying that the test matrix runs all of them but CI only runs the ones not in suites by default (I don't know if that's an accurate statement). [1] https://github.com/boostorg/gil/blob/master/test/Jamfile [2] https://github.com/boostorg/phoenix/blob/master/test/Jamfile