java-tutorials/spring-boot-autoconfiguration/src/test/java/com/baeldung/autoconfiguration/ConditionalOnClassTest.java

package com.baeldung.autoconfiguration;

import static org.assertj.core.api.Assertions.assertThat;

import org.junit.jupiter.api.Test;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
import org.springframework.boot.test.context.FilteredClassLoader;
import org.springframework.boot.test.context.runner.ApplicationContextRunner;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

public class ConditionalOnClassTest {

    private final ApplicationContextRunner contextRunner = new ApplicationContextRunner();

    @Test
    public void whenDependentClassIsPresent_thenBeanCreated() {
        this.contextRunner.withUserConfiguration(ConditionalOnClassConfiguration.class)
            .run(context -> {
                assertThat(context).hasBean("created");
                assertThat(context.getBean("created")).isEqualTo("This is created when ConditionalOnClassTest is present on the classpath");
            });
    }

    @Test
    public void whenDependentClassIsPresent_thenBeanMissing() {
        this.contextRunner.withUserConfiguration(ConditionalOnMissingClassConfiguration.class)
            .run(context -> {
                assertThat(context).doesNotHaveBean("missed");
            });
    }

    @Test
    public void whenDependentClassIsNotPresent_thenBeanMissing() {
        this.contextRunner.withUserConfiguration(ConditionalOnClassConfiguration.class)
            .withClassLoader(new FilteredClassLoader(ConditionalOnClassTest.class))
            .run((context) -> {
                assertThat(context).doesNotHaveBean("created");
                assertThat(context).doesNotHaveBean(ConditionalOnClassTest.class);

            });
    }

    @Test
    public void whenDependentClassIsNotPresent_thenBeanCreated() {
        this.contextRunner.withUserConfiguration(ConditionalOnMissingClassConfiguration.class)
            .withClassLoader(new FilteredClassLoader(ConditionalOnClassTest.class))
            .run((context) -> {
                assertThat(context).hasBean("missed");
                assertThat(context).getBean("missed")
                    .isEqualTo("This is missed when ConditionalOnClassTest is present on the classpath");
                assertThat(context).doesNotHaveBean(ConditionalOnClassTest.class);

            });
    }

    @Configuration
    @ConditionalOnClass(ConditionalOnClassTest.class)
    protected static class ConditionalOnClassConfiguration {
        @Bean
        public String created() {
            return "This is created when ConditionalOnClassTest is present on the classpath";
        }
    }

    @Configuration
    @ConditionalOnMissingClass("com.baeldung.autoconfiguration.ConditionalOnClassTest")
    protected static class ConditionalOnMissingClassConfiguration {
        @Bean
        public String missed() {
            return "This is missed when ConditionalOnClassTest is present on the classpath";
        }
    }

}