Test cases improvements

[bilal966]

tutorials/spring-boot/spring-boot2-junit5-mockito/src/test/java/com/frontbackend/springboot/controller/HelloControllerMockMvcTest.java

Line 23 in 96edd16

public void shouldReturnDefaultMessage() throws Exception {

This test case can be improved with 100% test coverage. I have fixed and want to push the code.