Add missing test to mutations_spec

Also adds expect(...).not.toBe to add assurance
that the state actually changed

spec/frontend/create_cluster/gke_cluster/stores/mutations_spec.js

@@ -9,18 +9,21 @@ import {
 
 describe('GCP Cluster Dropdown Store Mutations', () => {
   describe.each`
-    mutation                            | stateProperty                 | mockData
-    ${types.SET_PROJECTS}               | ${'projects'}                 | ${gapiProjectsResponseMock.projects}
-    ${types.SET_ZONES}                  | ${'zones'}                    | ${gapiZonesResponseMock.items}
-    ${types.SET_MACHINE_TYPES}          | ${'machineTypes'}             | ${gapiMachineTypesResponseMock.items}
-    ${types.SET_MACHINE_TYPE}           | ${'selectedMachineType'}      | ${gapiMachineTypesResponseMock.items[0].name}
-    ${types.SET_ZONE}                   | ${'selectedZone'}             | ${gapiZonesResponseMock.items[0].name}
-    ${types.SET_PROJECT}                | ${'selectedProject'}          | ${gapiProjectsResponseMock.projects[0]}
-    ${types.SET_PROJECT_BILLING_STATUS} | ${'projectHasBillingEnabled'} | ${true}
+    mutation                                   | stateProperty                   | mockData
+    ${types.SET_PROJECTS}                      | ${'projects'}                   | ${gapiProjectsResponseMock.projects}
+    ${types.SET_ZONES}                         | ${'zones'}                      | ${gapiZonesResponseMock.items}
+    ${types.SET_MACHINE_TYPES}                 | ${'machineTypes'}               | ${gapiMachineTypesResponseMock.items}
+    ${types.SET_MACHINE_TYPE}                  | ${'selectedMachineType'}        | ${gapiMachineTypesResponseMock.items[0].name}
+    ${types.SET_ZONE}                          | ${'selectedZone'}               | ${gapiZonesResponseMock.items[0].name}
+    ${types.SET_PROJECT}                       | ${'selectedProject'}            | ${gapiProjectsResponseMock.projects[0]}
+    ${types.SET_PROJECT_BILLING_STATUS}        | ${'projectHasBillingEnabled'}   | ${true}
+    ${types.SET_IS_VALIDATING_PROJECT_BILLING} | ${'isValidatingProjectBilling'} | ${true}
   `('$mutation', ({ mutation, stateProperty, mockData }) => {
     it(`should set the mutation payload to the ${stateProperty} state property`, () => {
       const state = createState();
 
+      expect(state[stateProperty]).not.toBe(mockData);
+
       mutations[mutation](state, mockData);
 
       expect(state[stateProperty]).toBe(mockData);