Fix regression using GenericContainer#setImage (#7820)

1dba8d1 introduced a breaking change. `GenericContainer#getImage`
returns the value of `ContainerDef#getImage` instead of `RemoteImageName`
because this is not set anymore when using `GenericContainer#setImage`.

Fixes #7819

Author: eddumelendez

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

@@ -267,6 +267,7 @@ public GenericContainer(@NonNull final Future<String> image) {
     }
 
     public void setImage(Future<String> image) {
+        this.image = new RemoteDockerImage(image);
         this.containerDef.setImage(new RemoteDockerImage(image));
     }
 

core/src/test/java/org/testcontainers/containers/GenericContainerTest.java

@@ -20,6 +20,7 @@
 import org.testcontainers.TestImages;
 import org.testcontainers.containers.startupcheck.StartupCheckStrategy;
 import org.testcontainers.containers.wait.strategy.AbstractWaitStrategy;
+import org.testcontainers.images.RemoteDockerImage;
 import org.testcontainers.images.builder.ImageFromDockerfile;
 import org.testcontainers.images.builder.Transferable;
 import org.testcontainers.utility.MountableFile;
@@ -222,6 +223,14 @@ public void testArchitectureCheck() {
         }
     }
 
+    @Test
+    public void shouldReturnTheProvidedImage() {
+        GenericContainer container = new GenericContainer(TestImages.REDIS_IMAGE);
+        assertThat(container.getImage().get()).isEqualTo("redis:3.0.2");
+        container.setImage(new RemoteDockerImage(TestImages.ALPINE_IMAGE));
+        assertThat(container.getImage().get()).isEqualTo("alpine:3.16");
+    }
+
     static class NoopStartupCheckStrategy extends StartupCheckStrategy {
 
         @Override