1. A computer-implemented method for client-side event logging, comprising: receiving, by a computer system, a set of executable components selected from a predefined collection of executable components to implement at least a test of a computer system state transition, the set of executable components including a set of test condition evaluation components and a set of network document browser event capture components optimized to obtain information to facilitate evaluation of a set of test conditions with the set of test condition evaluation components; injecting the set of executable components into an execution environment of a network document browser, the execution environment providing discontinuous access to the set of test condition evaluation components; during a first period of time when access to the set of test condition evaluation components is not available in the execution environment of the network document browser, recording, by the computer system, events relevant to the test with the injected set of network document browser event capture components; during a second period of time when access to the set of test condition evaluation components is available in the execution environment of the network document browser, evaluating, by the computer system, the set of test conditions based at least in part on information obtained by the injected set of test condition evaluation components and the events recorded by the injected set of network document browser event capture components; and providing one or more results of the evaluating for presentation to a user.