Fix extra newlines in container log / exec output (#3752)

Fixes #1763
Fixes #1854

Co-authored-by: Sergei Egorov <segorov@vmware.com>

Author: perlun

core/src/main/java/org/testcontainers/containers/output/ToStringConsumer.java

@@ -10,21 +10,14 @@
  * Created by rnorth on 26/03/2016.
  */
 public class ToStringConsumer extends BaseConsumer<ToStringConsumer> {
-    private static final byte[] NEW_LINE = "\n".getBytes();
-
-    private boolean firstLine = true;
     private ByteArrayOutputStream stringBuffer = new ByteArrayOutputStream();
 
     @Override
     public void accept(OutputFrame outputFrame) {
         try {
             if (outputFrame.getBytes() != null) {
-                if (!firstLine) {
-                    stringBuffer.write(NEW_LINE);
-                }
                 stringBuffer.write(outputFrame.getBytes());
                 stringBuffer.flush();
-                firstLine = false;
             }
         } catch (IOException e) {
             throw new RuntimeException(e);

core/src/test/java/org/testcontainers/containers/output/ToStringConsumerTest.java

@@ -0,0 +1,89 @@
+package org.testcontainers.containers.output;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.apache.commons.lang.RandomStringUtils;
+import org.assertj.core.api.Assertions;
+import org.junit.Test;
+import org.testcontainers.containers.Container.ExecResult;
+import org.testcontainers.containers.GenericContainer;
+import org.testcontainers.containers.startupcheck.OneShotStartupCheckStrategy;
+
+public class ToStringConsumerTest {
+
+    private static final String LARGE_PAYLOAD;
+
+    static {
+        StringBuilder builder = new StringBuilder(10_003 * 10);;
+        for (int i = 0; i < 10; i++) {
+            builder.append(' ').append(i).append(RandomStringUtils.randomAlphabetic(10000));
+        }
+        LARGE_PAYLOAD = builder.toString();
+        Assertions.assertThat(LARGE_PAYLOAD).doesNotContain("\n");
+    }
+
+    @Test
+    public void newlines_are_not_added_to_exec_output() throws Exception {
+        try (GenericContainer<?> container = new GenericContainer<>("alpine:3.13")) {
+            container.withCommand("sleep", "2m");
+            container.start();
+
+            ExecResult build = container.execInContainer("echo", "-n", LARGE_PAYLOAD);
+            Assertions.assertThat(build.getStdout())
+                .doesNotContain("\n")
+                .isEqualTo(LARGE_PAYLOAD);
+        }
+    }
+
+    @Test(timeout = 60_000L)
+    public void newlines_are_not_added_to_exec_output_with_tty() throws Exception {
+        try (GenericContainer<?> container = new GenericContainer<>("alpine:3.13")) {
+            container.withCreateContainerCmdModifier(cmd -> {
+                cmd
+                    .withAttachStdin(true)
+                    .withStdinOpen(true)
+                    .withTty(true);
+            });
+            container.withCommand("sleep", "2m");
+            container.start();
+
+            ExecResult build = container.execInContainer("echo", "-n", LARGE_PAYLOAD);
+            assertThat(build.getStdout())
+                .isEqualTo(LARGE_PAYLOAD)
+                .doesNotContain("\n");
+        }
+    }
+
+    @Test
+    public void newlines_are_not_added_to_container_output() {
+        try (GenericContainer<?> container = new GenericContainer<>("alpine:3.13")) {
+            container.withCommand("echo", "-n", LARGE_PAYLOAD);
+            container.setStartupCheckStrategy(new OneShotStartupCheckStrategy());
+            container.start();
+
+            container.getDockerClient().waitContainerCmd(container.getContainerId()).start().awaitStatusCode();
+
+            assertThat(container.getLogs())
+                .isEqualTo(LARGE_PAYLOAD)
+                .doesNotContain("\n");
+        }
+    }
+
+    @Test
+    public void newlines_are_not_added_to_container_output_with_tty() {
+        try (GenericContainer<?> container = new GenericContainer<>("alpine:3.13")) {
+            container.withCreateContainerCmdModifier(cmd -> {
+                cmd.withTty(true);
+            });
+            container.withCommand("echo", "-n", LARGE_PAYLOAD);
+            container.setStartupCheckStrategy(new OneShotStartupCheckStrategy());
+            container.start();
+
+            container.getDockerClient().waitContainerCmd(container.getContainerId()).start().awaitStatusCode();
+
+            assertThat(container.getLogs())
+                .isEqualTo(LARGE_PAYLOAD)
+                .doesNotContain("\n");
+        }
+    }
+}