Add test for adding steps to a Flow via "next"

Related to #4432

(cherry picked from commit 42dd144)

Author: Alexey Orlyansky

spring-batch-core/src/test/java/org/springframework/batch/core/job/builder/FlowJobBuilderTests.java

@@ -142,6 +142,15 @@ void testBuildSingleFlow() {
 		assertEquals(2, execution.getStepExecutions().size());
 	}
 
+	@Test
+	void testBuildSingleFlowAddingStepsViaNext() {
+		Flow flow = new FlowBuilder<Flow>("subflow").next(step1).next(step2).build();
+		FlowJobBuilder builder = new JobBuilder("flow", jobRepository).start(flow).end().preventRestart();
+		builder.build().execute(execution);
+		assertEquals(BatchStatus.COMPLETED, execution.getStatus());
+		assertEquals(2, execution.getStepExecutions().size());
+	}
+
 	@Test
 	void testBuildOverTwoLines() {
 		FlowJobBuilder builder = new JobBuilder("flow", jobRepository).start(step1).on("COMPLETED").to(step2).end();