Add @FunctionalSpringBootTest and mini web server

User can run a minimal HTTP app using an app that is a Function
or an ApplicationContextInitializer. Can also test using
@FunctionalSpringBootTest in place of @SpringBootTest.

Add some tests and documentation for functional beans

Make server.address configurable

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/test/FunctionalSpringBootTest.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2012-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.function.context.test;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.core.annotation.AliasFor;
+import org.springframework.test.context.ContextConfiguration;
+
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+@Inherited
+@org.springframework.boot.test.context.SpringBootTest(properties = "spring.functional.enabled=true", webEnvironment = WebEnvironment.NONE)
+@ContextConfiguration(loader = FunctionalTestContextLoader.class)
+public @interface FunctionalSpringBootTest {
+
+	@AliasFor(annotation=org.springframework.boot.test.context.SpringBootTest.class, attribute="properties")
+	String[] value() default {};
+
+	@AliasFor(annotation=org.springframework.boot.test.context.SpringBootTest.class, attribute="value")
+	String[] properties() default {};
+
+	@AliasFor(annotation=org.springframework.boot.test.context.SpringBootTest.class, attribute="classes")
+	Class<?>[] classes() default {};
+
+	@AliasFor(annotation=org.springframework.boot.test.context.SpringBootTest.class, attribute="webEnvironment")
+	WebEnvironment webEnvironment() default WebEnvironment.MOCK;
+
+}

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/test/FunctionalTestContextLoader.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.function.context.test;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.test.context.SpringBootContextLoader;
+import org.springframework.cloud.function.context.FunctionalSpringApplication;
+import org.springframework.cloud.function.context.config.ContextFunctionCatalogInitializer;
+
+/**
+ * A test context loader for Spring Boot applications that use the
+ * {@link ContextFunctionCatalogInitializer}.
+ * 
+ * @author Dave Syer
+ *
+ */
+public class FunctionalTestContextLoader extends SpringBootContextLoader {
+
+	@Override
+	protected SpringApplication getSpringApplication() {
+		return new FunctionalSpringApplication();
+	}
+}

spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/test/FunctionalTests.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2012-2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.function.context.test;
+
+import java.util.function.Function;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.cloud.function.context.FunctionCatalog;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import reactor.core.publisher.Flux;
+
+/**
+ * @author Dave Syer
+ *
+ */
+@RunWith(SpringRunner.class)
+@FunctionalSpringBootTest
+public class FunctionalTests {
+
+	@Autowired
+	private FunctionCatalog catalog;
+
+	@Test
+	public void words() throws Exception {
+		Function<Flux<String>, Flux<String>> function = catalog.lookup(Function.class,
+				"function");
+		assertThat(function.apply(Flux.just("foo")).blockFirst()).isEqualTo("FOO");
+	}
+
+	@SpringBootConfiguration
+	protected static class TestConfiguration implements Function<String, String> {
+		@Override
+		public String apply(String value) {
+			return value.toUpperCase();
+		}
+	}
+}