Gradle sourceSets: classesDir has been deprecated

I have seen similar posts but I am not quite sure what change should I make for my configuration. I recently upgraded to gradle 4.10 and started getting bunch of errors. I am pretty new to groovy.

Description

I have a gradle file uiTest.gradle

 1.   configurations {
 2.               uiTest
 3.           }
 4.           
 5.           sourceSets {
 6.               uiTest {
 7.                   java.srcDir file('src/uiTest/java')
 8.                   resources.srcDirs file('src/uiTest/resources')
 9.               }
 10.           }
 11.           
 12.           dependencies {
 13.               ...
 14.               uiTestCompile 'commons-io:commons-io:2.6'
 15.           }
 16.           
 17.           task uiTest(type: Test) {
 18.               include '**/*Test.class'
 19.           
 20.               dependsOn 'cleanUiTest'
 21.           
 22.               testClassesDir = sourceSets.uiTest.output.classesDir
 23.               classpath = sourceSets.uiTest.runtimeClasspath
 24.           
 25.               if (project.hasProperty('testEnv') && project.property('testEnv') != 'dev') {
 26.                  maxParallelForks = 4
 27.               } else {
 28.                   
 29.               }
 30.           
 31.           }

I get the error on line 22

Gradle now uses separate output directories for each JVM language, but this build assumes a single directory for all classes from a source set.

testClassesDir = sourceSets.uiTest.output.classesDir