Fix vararg problem

Fixes #9761

Author: jeffscottbrown

grails-plugin-validation/src/main/groovy/grails/validation/Validateable.groovy

@@ -78,18 +78,33 @@ trait Validateable {
         }
     }
 
+    boolean validate() {
+        validate null
+    }
     boolean validate(Closure<?>... adHocConstraintsClosures) {
         validate(null, null, adHocConstraintsClosures)
     }
 
+    boolean validate(Map<String, Object> params) {
+        validate params, null
+    }
+
     boolean validate(Map<String, Object> params, Closure<?>... adHocConstraintsClosures) {
         validate(null, params, adHocConstraintsClosures)
     }
 
+    boolean validate(List fieldsToValidate) {
+        validate fieldsToValidate, null
+    }
+
     boolean validate(List fieldsToValidate, Closure<?>... adHocConstraintsClosures) {
         validate(fieldsToValidate, null, adHocConstraintsClosures)
     }
 
+    boolean validate(List fieldsToValidate, Map<String, Object> params) {
+        validate fieldsToValidate, params, null
+    }
+
     boolean validate(List fieldsToValidate, Map<String, Object> params, Closure<?>... adHocConstraintsClosures) {
         beforeValidateHelper.invokeBeforeValidate(this, fieldsToValidate)
 

grails-test-suite-uber/src/test/groovy/grails/validation/ValidateableMockSpec.groovy

@@ -0,0 +1,29 @@
+package grails.validation
+
+import spock.lang.Issue
+import spock.lang.Specification
+
+class ValidateableMockSpec extends Specification {
+
+    @Issue('grails/grails-core#9761')
+    void 'ensure command is mocked properly'(){
+        given:
+        SomeCommand command = GroovyMock()
+        1 * command.validate() >> true
+        1 * command.validate() >> false
+        1 * command.validate() >> true
+        1 * command.validate(_) >> true
+        1 * command.validate(_) >> false
+        1 * command.validate(_, _) >> true
+
+        expect:
+        command.validate()
+        !command.validate()
+        command.validate()
+        command.validate([])
+        !command.validate([:])
+        command.validate([], [:])
+    }
+}
+
+class SomeCommand implements Validateable {}