Add some integration tests for the CLI’s quiet mode

See gh-6918

spring-boot-cli/src/it/resources/run-command/quiet.groovy

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+package org.test
+
+@Component
+class Example implements CommandLineRunner {
+
+	void run(String... args) {
+		print "Ssshh"
+	}
+
+}

spring-boot-cli/src/test/java/org/springframework/boot/cli/RunCommandIntegrationTests.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2012-2016 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.cli;
+
+import java.util.Properties;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+
+import org.springframework.boot.cli.command.run.RunCommand;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for {@link RunCommand}.
+ *
+ * @author Andy Wilkinson
+ */
+public class RunCommandIntegrationTests {
+
+	@Rule
+	public CliTester cli = new CliTester("src/it/resources/run-command/");
+
+	private Properties systemProperties = new Properties();
+
+	@Before
+	public void captureSystemProperties() {
+		this.systemProperties.putAll(System.getProperties());
+	}
+
+	@After
+	public void restoreSystemProperties() {
+		System.setProperties(this.systemProperties);
+	}
+
+	@Test
+	public void bannerAndLoggingIsOutputByDefault() throws Exception {
+		String output = this.cli.run("quiet.groovy");
+		assertThat(output).contains(" :: Spring Boot ::");
+		assertThat(output).contains("Starting application");
+		assertThat(output).contains("Ssshh");
+	}
+
+	@Test
+	public void quietModeSuppressesAllCliOutput() throws Exception {
+		String output = this.cli.run("quiet.groovy", "-q");
+		assertThat(output).isEqualTo("Ssshh");
+	}
+
+}