Tip #18: (Spring) Use CapturedOutput Extension to test log output.

I had this requirement once, the system should log this and that…

How can I test logs?

If you are a Spring user, you can use CapturedOutput.

 @Test
 @ExtendWith(OutputCaptureExtension.class)
 void testLogOutput(CapturedOutput output) {
    //make your normal call here
    //now you can test output here 
    assertThat(output.getOut()).contains(“my expected log”);
 }

I’m not a Spring user, how can I do it?

Well, you can add handlers/appenders on your Logger to test it.

Have you ever needed to test your output? Let me know your use case!

Happy coding!