testlog

func ToTempDir ¶

func ToTempDir() (dir string, release func() error, err error)

ToTempDir points every log stream at a new scratch directory in file mode, and returns the directory with the function that removes it. It exports the settings through the environment, where config.Init reads them, and writes them to config.App.Logger as well, for a process that initializes the loggers without config.Init; either way it runs before the loggers come up.

File mode alone does not keep the logs out of the test output: the global stream still writes to stdout when it names no file, and the console mirror copies it there when it names one. So the global stream gets a file of its own and the mirror is turned off.

The files are not evidence a test can read back: the directory goes away at release, and every file sink buffers its entries (see the buffered writer in the logger package), so a test process that ends within the flush interval leaves most of them empty. A test that needs to assert on log output instead swaps the package logger it cares about for a scratch file logger under its own t.TempDir and flushes that one before reading — see withCronjobLoggerConfig and readLogEntry in the cronjob tests.

The release stops the log writers before it removes the directory. They hold entries back for up to a second, and a file writer opens its file on its first write, creating the directory when it is missing, so a write arriving after the removal would recreate the directory and leave it behind.