(1) In general, a "safety property" as you discuss it, is basically a validation step: Some property has to be TRUE or FALSE for the test to PASS or FAIL.
eValid has a variety of validation commands, as described here:
http://www.e-Valid.com/Products/Documentation.9/Testing/validation.htmlAnd, eValid has a powerful built-in facility that lets you Validate page properties in terms of the internal page DOM, and the capability can also be used to set up Validations that apply Adaptive Playback to prevent Validation failures when pages experience maintenance:
http://www.e-Valid.com/Products/Documentation.9/Validation/validate.selected.object.html(2) It's unclear what you mean by "too fast". In a well configured eValid test the playbacks are all self-synchronizing, so if the server gets slower then BU-based playbacks don't get out of sync.
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The eValid Support Team