Change getUniqueJobParameters() to use random number generator that has a lower chance of repeating

Issue #821

Author: saikatbhadra

spring-batch-test/src/main/java/org/springframework/batch/test/JobLauncherTestUtils.java

@@ -16,6 +16,7 @@
 
 package org.springframework.batch.test;
 
+import java.security.SecureRandom;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -160,7 +161,7 @@ public JobExecution launchJob(JobParameters jobParameters) throws Exception {
 	 */
 	public JobParameters getUniqueJobParameters() {
 		Map<String, JobParameter> parameters = new HashMap<>();
-		parameters.put("random", new JobParameter((long) (Math.random() * JOB_PARAMETER_MAXIMUM)));
+		parameters.put("random", new JobParameter(new SecureRandom().nextLong()));
 		return new JobParameters(parameters);
 	}
 

spring-batch-test/src/test/java/org/springframework/batch/test/JobLauncherTestUtilsTests.java

@@ -20,6 +20,7 @@
 import org.springframework.batch.core.ExitStatus;
 import org.springframework.batch.core.Job;
 import org.springframework.batch.core.JobExecution;
+import org.springframework.batch.core.JobParameters;
 import org.springframework.batch.core.Step;
 import org.springframework.batch.core.StepContribution;
 import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;
@@ -35,7 +36,11 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.lang.Nullable;
 
+import java.util.HashSet;
+import java.util.Set;
+
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 
 /**
  * @author mminella
@@ -53,6 +58,18 @@ public void testStepExecutionWithJavaConfig() {
 		assertEquals(ExitStatus.COMPLETED, execution.getExitStatus());
 	}
 
+	@Test
+	public void getUniqueJobParameters_doesNotRepeatJobParameters() {
+		ApplicationContext context = new AnnotationConfigApplicationContext(TestJobConfiguration.class);
+		JobLauncherTestUtils testUtils = context.getBean(JobLauncherTestUtils.class);
+		Set<JobParameters> jobParametersSeen = new HashSet<>();
+		for (int i = 0; i < 10_000; i++) {
+			JobParameters jobParameters = testUtils.getUniqueJobParameters();
+			assertFalse(jobParametersSeen.contains(jobParameters));
+			jobParametersSeen.add(jobParameters);
+		}
+	}
+
 	@Configuration
 	@EnableBatchProcessing
 	public static class TestJobConfiguration {