Added test case that I missed to migrate and converted it it spock

src/test/groovy/grails/plugin/zipcitystate/ZipCodeControllerSpec.groovy

@@ -0,0 +1,41 @@
+package grails.plugin.zipcitystate
+
+import grails.test.mixin.Mock
+import grails.test.mixin.TestFor
+import spock.lang.Specification
+import spock.lang.Unroll
+
+@TestFor(ZipCodeController)
+@Mock([ZipCode,ZipCodeService])
+class ZipCodeControllerSpec extends Specification{
+
+    @Unroll
+    void "Lookup for zipcode:#code returns city:#city and state:#state"() {
+        given: "a saved ZipCode"
+            new ZipCode(code:code, city:city, state:state).save()
+
+        and: "lookup for an existing code"
+            controller.lookup(code)
+
+        expect: 'the correct code, city and state'
+            response.json.code == expectedCode
+            response.json.city == expectedCity
+            response.json.state == expectedState
+
+        where:
+            code    | city       | state || expectedCode || expectedCity || expectedState
+            '02135' | 'Brighton' | 'MA'  || '02135'      || 'Brighton'   || 'MA'
+            '02067' | 'Sharon'   | 'MA'  || '02067'      || 'Sharon'     || 'MA'
+    }
+
+    void "Lookup for a non-existing zipcode returns no city and state"() {
+        when: 'lookup for a non-existing zipcode'
+            controller.lookup('00001')
+
+        then: 'response contains no code, city and state'
+            !response.json.code
+            !response.json.city
+            !response.json.state
+    }
+
+}