@Test
public void testFormatLogMessage_code_is_empty() {

    // do setup.
    String code = "";
    String message = "message";
    // do test.
    String actualLogMessage = testTarget.formatLogMessage(code, message);
    // do assert.
    String expectedLogMessage = "[UNDEFINED-CODE] " + message;
    assertThat(actualLogMessage, is(expectedLogMessage));
}