@Test
    void test() {
        assertEquals(Duration.ofSeconds(-1), this.grpcServerProperties.getShutdownGracePeriod());
    }
Tests whether the property resolution works with negative values and without suffixes.
grpc-server-spring-boot-starter/src/test/java/net/devh/boot/grpc/server/config/GrpcServerPropertiesNegativeNoUnitTest.java