test: check block height in mocked e2e tests

apps/trading-e2e/src/integration/home.cy.ts

@@ -304,4 +304,11 @@ describe('home', { tags: '@regression' }, () => {
       });
     });
   });
+
+  describe('footer', () => {
+    it('shows current block height', () => {
+      cy.visit('/');
+      cy.getByTestId('app-footer').contains('Operational').contains('100');
+    });
+  });
 });

apps/trading/components/footer/footer.tsx

@@ -13,7 +13,10 @@ export const Footer = () => {
   const { blockDiff, datanodeBlockHeight } = useNodeHealth();
 
   return (
-    <footer className="px-4 py-1 text-xs border-t border-default text-vega-light-300 dark:text-vega-dark-300">
+    <footer
+      data-testid="app-footer"
+      className="px-4 py-1 text-xs border-t border-default text-vega-light-300 dark:text-vega-dark-300"
+    >
       {/* Pull left to align with top nav, due to button padding */}
       <div className="-ml-2">
         {VEGA_URL && (

libs/cypress/src/lib/mock-gql.ts

@@ -32,7 +32,8 @@ export const aliasGQLQuery = (
   operationName: string,
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   data?: any,
-  errors?: Partial<GraphQLError>[]
+  errors?: Partial<GraphQLError>[],
+  headers?: Record<string, string>
 ) => {
   if (hasOperationName(req, operationName)) {
     req.alias = operationName;
@@ -40,6 +41,13 @@ export const aliasGQLQuery = (
       req.reply({
         statusCode: 200,
         body: { ...(data && { data }), ...(errors && { errors }) },
+        headers: {
+          ...req.headers,
+          // basic default block height header response
+          'x-block-height': '100',
+          'x-block-timestamp': Date.now().toString() + '0'.repeat(6),
+          ...headers,
+        },
       });
     }
   }

libs/environment/src/hooks/use-node-health.ts

@@ -4,14 +4,16 @@ import { useHeaderStore } from '@vegaprotocol/apollo-client';
 import { useEnvironment } from './use-environment';
 import { fromNanoSeconds } from '@vegaprotocol/react-helpers';
 
+const POLL_INTERVAL = 1000;
+
 export const useNodeHealth = () => {
   const url = useEnvironment((store) => store.VEGA_URL);
   const headerStore = useHeaderStore();
   const headers = url ? headerStore[url] : undefined;
-  const { data, error, loading, stopPolling } = useStatisticsQuery({
-    pollInterval: 1000,
-    fetchPolicy: 'no-cache',
-  });
+  const { data, error, loading, startPolling, stopPolling } =
+    useStatisticsQuery({
+      fetchPolicy: 'no-cache',
+    });
 
   const blockDiff = useMemo(() => {
     if (!data?.statistics.blockHeight) {
@@ -28,8 +30,13 @@ export const useNodeHealth = () => {
   useEffect(() => {
     if (error) {
       stopPolling();
+      return;
     }
-  }, [error, stopPolling]);
+
+    if (!('Cypress' in window)) {
+      startPolling(POLL_INTERVAL);
+    }
+  }, [error, startPolling, stopPolling]);
 
   return {
     error,