Add support for initialization scripts

modules/mongodb/src/main/java/org/testcontainers/containers/MongoDBContainer.java

@@ -223,4 +223,23 @@ void withSharding() {
             setEntrypoint("sh");
         }
     }
+
+    /**
+     * Executes a MongoDB initialization script from the classpath during startup.
+     * <p>
+     * The script will be copied to {@code /docker-entrypoint-initdb.d/init.js}.
+     * This method also adjusts the {@link org.testcontainers.containers.wait.strategy.WaitStrategy}
+     * to expect the "waiting for connections" log message twice, as the execution of an init script
+     * causes MongoDB to restart.
+     *
+     * @param scriptPath the path to the init script file on the classpath
+     * @return this container instance
+     */
+    public MongoDBContainer withInitScript(String scriptPath) {
+        withCopyFileToContainer(MountableFile.forClasspathResource(scriptPath), "/docker-entrypoint-initdb.d/init.js");
+
+        this.waitStrategy = Wait.forLogMessage("(?i).*waiting for connections.*", 2);
+
+        return this;
+    }
 }

modules/mongodb/src/test/java/org/testcontainers/mongodb/MongoDBInitScriptTest.java

@@ -0,0 +1,27 @@
+package org.testcontainers.containers;
+
+import org.junit.jupiter.api.Test;
+
+import java.time.Duration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class MongoDBInitScriptTest {
+
+    @Test
+    void testWithInitScript() {
+        // Start the container using try-with-resources to ensure it closes automatically
+        try (
+            MongoDBContainer mongoDB = new MongoDBContainer("mongo:4.0.10")
+                // Configure the init script. This triggers a restart inside the container,
+                // so the container must wait for the second "waiting for connections" log message.
+                .withInitScript("init.js")
+                .withStartupTimeout(Duration.ofSeconds(30))
+        ) {
+            mongoDB.start();
+
+            // Assert that the container started successfully
+            assertThat(mongoDB.isRunning()).isTrue();
+        }
+    }
+}

modules/mongodb/src/test/resources/init.js

@@ -0,0 +1 @@
+db.createCollection("test_collection");