@Test
    public void testDatabaseThreadPool() {
        assertEquals(10, dbServer.getThreadPool());
    }
Simulate Spring Boot Application behaviour of loading properties
1. Properties from @TestPropertySource
2. The application.properties or application.yml from the src/test/resources directory.
3. The application.properties or application.yml from the src/main/resources directory.
<p>
In this case, application.properties from the src/main/resources is loaded.
spring-boot-externalize-config-4/src/test/java/com/mkyong/ApplicationTest2.java