Examining server logs from jstests is sometimes necessary (eg. to check behaviour of commands that aren't profiled, such as auth admin commands or update/delete bulk commands (SERVER-23266)). This is typically done using the getLog command (or the checkLog shell helper). However, the current RamLog line length limit may be overrun, especially for commands in sharded environments. This makes tests that need to examine the logs this way inherently fragile.

Simply increasing the maximum length adds only modest memory usage, but may have implications for any downstream users of the getLog command (especially if the getLog output is stored/processed). So a better solution would be to increase the maximum line length only during testing, ie. when --enableTestCommands has been specified. This would allow the fragility of log-based tests to be greatly reduced, without affecting non-test consumers of getLog output.