[FIXED] How to test @Configuration class in Spring without starting up whole context?

Issue

How can I test my configuration without starting the whole Spring context class or should I do that?

@Configuration
public class GaRuConfig {

    @Bean
    public List<GaRu> rules(){
        SSRule rule1 = new SSRule();
        CSRule rule2 = new CSRule();
        DGRule rule3 = new DGRule();
        EGRule rule4 = new EGRule();

        return List.of(rule1, rule2, rule3, rule4);
    }
}

Is there a way to test this class?

Solution

Using AssertJ you can do the following:

public class GaRuConfigTest {

    private GaRuConfig gaRuConfig = new GaRuConfig();

    @Test
    public void shouldReturnCorrectListOfRulesWhenRequested() {
        // Act
        List<GaRu> rules = this.gaRuConfig.rules();

        // Assert
        Assertions.assertThat(rules.stream().filter(rule -> SSRule.class == rule.getClass()).collect(Collectors.toList())).isNotEmpty();
        Assertions.assertThat(rules.stream().filter(rule -> CSRule.class == rule.getClass()).collect(Collectors.toList())).isNotEmpty();
        Assertions.assertThat(rules.stream().filter(rule -> DGRule.class == rule.getClass()).collect(Collectors.toList())).isNotEmpty();
        Assertions.assertThat(rules.stream().filter(rule -> EGRule.class == rule.getClass()).collect(Collectors.toList())).isNotEmpty();
        
        Assertions.assertThat(rules).hasSize(4);
        Assertions.assertThat(SSRule.class == rules.get(0).getClass()).isTrue();
        Assertions.assertThat(CSRule.class == rules.get(1).getClass()).isTrue();
        Assertions.assertThat(DGRule.class == rules.get(2).getClass()).isTrue();
        Assertions.assertThat(EGRule.class == rules.get(3).getClass()).isTrue();
    }
}

Answered By - João Dias
Answer Checked By - Katrina (JavaFixing Volunteer)