@Test
    public void testGetExtensionLoaderNoJoinSPI() {
        try {
            ExtensionLoader.getExtensionLoader(NoJoinSPI.class).getJoin("subNoJoinSPI");
            fail();
        } catch (IllegalStateException expected) {
            assertThat(expected.getMessage(),
                    containsString("load extension resources error,class org.apache.shenyu.spi.fixture.SubNoJoinSPI without @interface org.apache.shenyu.spi.Join annotation"));
        }
    }
test ExtensionLoader.getJoin() param no join case.
shenyu-spi/src/test/java/org/apache/shenyu/spi/ExtensionLoaderTest.java