A testing unit implemented using software and/or hardware components, the testing unit being configured to store, in storage means, a plurality of input sets, each of which includes one or more client device inputs, and a plurality of first result values, each of which was obtained by an image rendering process using one of the plurality of input sets, wherein each one of the plurality of first result values is associated with one of the plurality of input sets that was input to the image rendering process at a time when the one of the plurality of first result values was obtained; wherein the testing unit comprises: retrieving means configured to retrieve an input set out of the plurality of input sets from the storage means; providing means configured to provide a system for image rendering (270, 280) with the retrieved input set; obtaining means configured to obtain, from the system (270, 280), a second result value by the image rendering process performed by the system (270, 280) using the retrieved input set; checking means configured to check each of the plurality of first result values to determine whether the second result value matches one of the plurality of first result values stored in the storage means, wherein no match indicates that the second result value does not match any of the stored first result values; and outputting means configured to output a result indicating that the image rendering process is abnormally stopped in a case where the second result value does not match any of the plurality of first result values; wherein the retrieving means is further configured to retrieve, in a case where the second result value matches one of the plurality of first result values, one of the plurality of input sets associated with the matched one of the plurality of first result values, and the providing means is further configured to provide the system (270, 280) with the retrieved one of the plurality of input sets. a plurality of input sets, each of which includes one or more client device inputs, and a plurality of first result values, each of which was obtained by an image rendering process using one of the plurality of input sets, wherein each one of the plurality of first result values is associated with one of the plurality of input sets that was input to the image rendering process at a time when the one of the plurality of first result values was obtained; wherein the testing unit comprises: retrieving means configured to retrieve an input set out of the plurality of input sets from the storage means; providing means configured to provide a system for image rendering (270, 280) with the retrieved input set; obtaining means configured to obtain, from the system (270, 280), a second result value by the image rendering process performed by the system (270, 280) using the retrieved input set; checking means configured to check each of the plurality of first result values to determine whether the second result value matches one of the plurality of first result values stored in the storage means, wherein no match indicates that the second result value does not match any of the stored first result values; and outputting means configured to output a result indicating that the image rendering process is abnormally stopped in a case where the second result value does not match any of the plurality of first result values; retrieving means configured to retrieve an input set out of the plurality of input sets from the storage means; providing means configured to provide a system for image rendering (270, 280) with the retrieved input set; obtaining means configured to obtain, from the system (270, 280), a second result value by the image rendering process performed by the system (270, 280) using the retrieved input set; checking means configured to check each of the plurality of first result values to determine whether the second result value matches one of the plurality of first result values stored in the storage means, wherein no match indicates that the second result value does not match any of the stored first result values; and outputting means configured to output a result indicating that the image rendering process is abnormally stopped in a case where the second result value does not match any of the plurality of first result values; wherein the retrieving means is further configured to retrieve, in a case where the second result value matches one of the plurality of first result values, one of the plurality of input sets associated with the matched one of the plurality of first result values, and the providing means is further configured to provide the system (270, 280) with the retrieved one of the plurality of input sets.