Support expressing application `args` in `@SpringBootTest`

Add `args` property to the `@SpringBootTest` annotation so tests
can easily supply application arguments to pass to their app under test.

See gh-14823

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -6752,6 +6752,17 @@ NOTE: If you directly use `@ComponentScan` (that is, not through
 `@SpringBootApplication`) you need to register the `TypeExcludeFilter` with it. See
 {dc-spring-boot}/context/TypeExcludeFilter.{dc-ext}[the Javadoc] for details.
 
+[[boot-features-testing-spring-boot-applications-arguments]]
+==== Testing with Application Arguments
+
+If your application expects <<boot-features-application-arguments,arguments>>, you can
+have `@SpringBootTest` inject them using the `args` field.
+
+[source,java,indent=0]
+----
+include::{test-examples}/context/ApplicationArgumentsExampleTests.java[tag=args]
+}
+----
 
 [[boot-features-testing-spring-boot-applications-testing-with-mock-environment]]
 ==== Testing with a mock environment

spring-boot-project/spring-boot-docs/src/test/java/org/springframework/boot/docs/context/ApplicationArgumentsExampleTests.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.boot.docs.context;
+
+// tag::args[]
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.ApplicationArguments;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(args = { "--foo=bar" })
+public class ApplicationArgumentsExampleTests {
+
+	@Autowired
+	private ApplicationArguments args;
+
+	@Test
+	public void applicationArgumentsPopulated() {
+		assertThat(this.args.getOptionNames()).contains("foo");
+		assertThat(this.args.getOptionValues("foo")).contains("bar");
+	}
+
+	// end::args[]
+	@Configuration
+	protected static class Config {
+
+	}
+
+}

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/SpringBootContextLoader.java

@@ -124,7 +124,7 @@ public class SpringBootContextLoader extends AbstractContextLoader {
 			application.setWebApplicationType(WebApplicationType.NONE);
 		}
 		application.setInitializers(initializers);
-		return application.run();
+		return application.run(getArgs(config));
 	}
 
 	/**
@@ -145,6 +145,19 @@ public class SpringBootContextLoader extends AbstractContextLoader {
 		return new StandardEnvironment();
 	}
 
+	/**
+	 * Get the {@link SpringBootTest#args()} (if present) specified in the annotated test
+	 * class. If no args given, returns empty array.
+	 * @param config the source context configuration
+	 * @return the {@link SpringBootTest#args()} (if present) specified in the annotated
+	 * test class, or empty array
+	 */
+	protected String[] getArgs(MergedContextConfiguration config) {
+		SpringBootTest annotation = AnnotatedElementUtils
+				.findMergedAnnotation(config.getTestClass(), SpringBootTest.class);
+		return (annotation != null) ? annotation.args() : new String[0];
+	}
+
 	private void setActiveProfiles(ConfigurableEnvironment environment,
 			String[] profiles) {
 		TestPropertyValues

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/SpringBootTest.java

@@ -106,6 +106,12 @@ public @interface SpringBootTest {
 	 */
 	Class<?>[] classes() default {};
 
+	/**
+	 * Arguments that should be passed to the application under test.
+	 * @return the arguments to pass to the application under test.
+	 */
+	String[] args() default {};
+
 	/**
 	 * The type of web environment to create when applicable. Defaults to
 	 * {@link WebEnvironment#MOCK}.

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/SpringBootTestArgsTests.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2012-2017 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.boot.test.context;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.ApplicationArguments;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Assert that tests annotated with {@link SpringBootTest} can specify
+ * {@link SpringBootTest#args()} to be passed to their application under test.
+ *
+ * @author Justin Griffin
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(args = { "--option.foo=option-foo-value", "other.bar=other-bar-value" })
+public class SpringBootTestArgsTests {
+
+	@Autowired
+	private ApplicationArguments args;
+
+	@Test
+	public void applicationArgumentsPopulated() {
+		assertThat(this.args.getOptionNames()).contains("option.foo");
+		assertThat(this.args.getNonOptionArgs()).contains("other.bar=other-bar-value");
+	}
+
+	@Configuration
+	protected static class Config {
+
+	}
+
+}