Abstract: Apparatus and method for testing of a telecommunications network, which uses a passive monitoring system to generate actual customer usage data concerning the telecommunications network. An active test manager uses the actual customer usage data to instantiate a set of test templates from a store of predetermined test templates, the test template describing a sequence of user actions performed in the network. The test templates include at least one test variable, which is updated by the active test manager, using the actual customer usage data, to generate a test, or set of tests. The generated test, or set of tests are then used by an active testing module to actively test the telecommunications network, hence the tests are updated using the latest data on customer usage.