Skip execInContainer(...) null or empty command parts.

Author: bedla

core/src/main/java/org/testcontainers/containers/ExecInContainerPattern.java

@@ -16,8 +16,10 @@
 import java.io.IOException;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.stream.Collectors;
 
 /**
@@ -199,7 +201,11 @@ public Container.ExecResult execInContainer(
         String containerId = containerInfo.getId();
         String containerName = containerInfo.getName();
 
-        String[] command = execConfig.getCommand();
+        String[] command = Arrays
+            .stream(execConfig.getCommand())
+            .filter(Objects::nonNull)
+            .filter(str -> !str.trim().isEmpty())
+            .toArray(String[]::new);
         log.debug("{}: Running \"exec\" command: {}", containerName, String.join(" ", command));
         final ExecCreateCmd execCreateCmd = dockerClient
             .execCreateCmd(containerId)

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

@@ -3,6 +3,9 @@
 import org.assertj.core.api.Assumptions;
 import org.junit.jupiter.api.AutoClose;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.NullSource;
+import org.junit.jupiter.params.provider.ValueSource;
 import org.testcontainers.TestImages;
 import org.testcontainers.containers.ExecConfig;
 import org.testcontainers.containers.GenericContainer;
@@ -36,6 +39,19 @@ void shouldExecuteCommand() throws Exception {
         // We expect to reach this point for modern Docker versions.
     }
 
+    @ParameterizedTest
+    @NullSource
+    @ValueSource(strings = { "", " ", "  " })
+    void shouldExecuteCommandAndSkipCommand(String commandParam) throws Exception {
+        Assumptions.assumeThat(TestEnvironment.dockerExecutionDriverSupportsExec()).isTrue();
+
+        final GenericContainer.ExecResult result = redis.execInContainer("redis-cli", commandParam, "role");
+        assertThat(result.getStdout())
+            .as("Output for \"redis-cli role\" command should start with \"master\"")
+            .startsWith("master");
+        assertThat(result.getStderr()).as("Stderr for \"redis-cli role\" command should be empty").isEmpty();
+    }
+
     @Test
     void shouldExecuteCommandWithUser() throws Exception {
         // The older "lxc" execution driver doesn't support "exec". At the time of writing (2016/03/29),