Fix fixed host port test (#1355)

* 'fix fixed host port test' - rewrote test using simple echo http container, followed path of original test;

* 'fix fixed host port test' - rewrote assertions to hamcrest, failure in response getting now fails test directly with io exc

* 'fix fixed host port test' - as suggested by reviewer, rewrote tests to alpine, also copied some routines from generic container tests

* 'fix fixed host port test' - no assertions on basic container start, code style updates based on PR

core/src/test/java/org/testcontainers/junit/FixedHostPortContainerTest.java

@@ -1,10 +1,19 @@
 package org.testcontainers.junit;
 
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import com.google.common.util.concurrent.Uninterruptibles;
 import org.junit.Test;
+import org.rnorth.ducttape.unreliables.Unreliables;
 import org.testcontainers.containers.FixedHostPortGenericContainer;
 import org.testcontainers.containers.GenericContainer;
 
+import java.io.BufferedReader;
 import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.Socket;
+import java.util.concurrent.TimeUnit;
 
 /**
  * Test of {@link FixedHostPortGenericContainer}. Note that this is not an example of typical use (usually, a container
@@ -14,28 +23,74 @@
  */
 public class FixedHostPortContainerTest {
 
-    private static final int REDIS_PORT = 6379;
+    private static final String TEST_IMAGE = "alpine:3.2";
+
+    /**
+     * Default http server port (just something different from default)
+     */
+    private static final int TEST_PORT = 5678;
+
+    /**
+     * test response
+     */
+    private static final String TEST_RESPONSE = "test-response";
+
+    /**
+     * *nix pipe to fire test response on test port
+     */
+    private static final String HTTP_ECHO_CMD =
+        String.format("while true; do echo \"%s\" | nc -l -p %d; done", TEST_RESPONSE, TEST_PORT);
 
     @Test
     public void testFixedHostPortMapping() throws IOException {
         // first find a free port on the docker host that will work for testing
-        GenericContainer portDiscoveryRedis = new GenericContainer("redis:3.0.2").withExposedPorts(REDIS_PORT);
-        portDiscoveryRedis.start();
-        Integer freePort = portDiscoveryRedis.getMappedPort(REDIS_PORT);
-        portDiscoveryRedis.stop();
-
-
-        // Set up a FixedHostPortGenericContainer as if this were a @Rule
-        FixedHostPortGenericContainer redis = new FixedHostPortGenericContainer("redis:3.0.2").withFixedExposedPort(freePort, REDIS_PORT);
-        redis.start();
-
-//        Config redisConfig = new Config();
-//        redisConfig.useSingleServer().setAddress(redis.getContainerIpAddress() + ":" + freePort);
-//        Redisson redisson = Redisson.create(redisConfig);
-//
-//        redisson.getBucket("test").set("foo");
-//
-//        assertEquals("The bucket content was successfully set", "foo", redisson.getBucket("test").get());
-//        assertEquals("The container returns the fixed port from getMappedPort(...)", freePort, redis.getMappedPort(REDIS_PORT));
+        final Integer unusedHostPort;
+        try (
+            final GenericContainer echoServer = new GenericContainer<>(TEST_IMAGE)
+                .withExposedPorts(TEST_PORT)
+                .withCommand("/bin/sh", "-c", HTTP_ECHO_CMD)
+        ) {
+            echoServer.start();
+            unusedHostPort = echoServer.getMappedPort(TEST_PORT);
+        }
+
+        // now starting echo server container mapped to known-as-free host port
+        try (
+            final GenericContainer echoServer = new FixedHostPortGenericContainer(TEST_IMAGE)
+            // using workaround for port bind+expose
+            .withFixedExposedPort(unusedHostPort, TEST_PORT)
+            .withExposedPorts(TEST_PORT)
+            .withCommand("/bin/sh", "-c", HTTP_ECHO_CMD)
+        ) {
+            echoServer.start();
+
+            assertThat("Port mapping does not seem to match given fixed port",
+                echoServer.getMappedPort(TEST_PORT), equalTo(unusedHostPort));
+
+            final String content = this.readResponse(echoServer, unusedHostPort);
+            assertThat("Returned echo from fixed port does not match expected", content, equalTo(TEST_RESPONSE));
+        }
+    }
+
+    /**
+     * Simple socket content reader from given container:port
+     *
+     * @param container to query
+     * @param port      to send request to
+     * @return socket reader content
+     * @throws IOException if any
+     */
+    private String readResponse(GenericContainer container, Integer port) throws IOException {
+        try (
+            final BufferedReader reader = Unreliables.retryUntilSuccess(10, TimeUnit.SECONDS,
+                () -> {
+                    Uninterruptibles.sleepUninterruptibly(1, TimeUnit.SECONDS);
+                    final Socket socket = new Socket(container.getContainerIpAddress(), port);
+                    return new BufferedReader(new InputStreamReader(socket.getInputStream()));
+                }
+            )
+        ) {
+            return reader.readLine();
+        }
     }
 }