added tests for explicit null

Author: rahulshishodia

grails-gradle/plugins/src/test/groovy/org/grails/gradle/plugin/core/GrailsGradlePreserveParametersSpec.groovy

@@ -24,6 +24,17 @@ class GrailsGradlePreserveParametersSpec extends GradleSpecification {
         result.output.contains("HAS_PRESERVE_PARAM_ENABLED=false")
     }
 
+    def "preserveParameterNames is set to false when configured as explicit null"() {
+        given:
+        setupTestResourceProject('preserve-params-null')
+
+        when:
+        def result = executeTask('inspectPreserveParam')
+
+        then:
+        result.output.contains("HAS_PRESERVE_PARAM_ENABLED=false")
+    }
+
     def "GroovyCompile tasks get parameters = true when preserveParameterNames is enabled"() {
         given:
         setupTestResourceProject('preserve-params-enabled')

grails-gradle/plugins/src/test/resources/test-projects/preserve-params-null/build.gradle

@@ -0,0 +1,15 @@
+plugins {
+    id 'org.apache.grails.gradle.grails-app'
+}
+
+grails {
+    preserveParameterNames = null
+}
+
+tasks.register('inspectPreserveParam') {
+    doLast {
+        def compileTasks = tasks.withType(GroovyCompile)
+        def paramsEnabled = compileTasks.every { it.groovyOptions.parameters }
+        println "HAS_PRESERVE_PARAM_ENABLED=${paramsEnabled}"
+    }
+}

grails-gradle/plugins/src/test/resources/test-projects/preserve-params-null/gradle.properties

@@ -0,0 +1 @@
+grailsVersion=__PROJECT_VERSION__

grails-gradle/plugins/src/test/resources/test-projects/preserve-params-null/grails-app/conf/application.yml

@@ -0,0 +1 @@
+rootProject.name = 'test-preserve-params-null'