test: Add integration test for ListHeaders (#3212)

<!--- Provide a general summary of your changes in the Title above -->

## Description
<!--- Describe your changes in detail -->
Adds a simple integration test for checking the heights returned from ListHeaders gRPC 

## Motivation and Context
<!--- Why is this change required? What problem does it solve? -->
<!--- If it fixes an open issue, please link to the issue here. -->
Increased test coverage 

## How Has This Been Tested?
<!--- Please describe in detail how you tested your changes. -->
<!--- Include details of your testing environment, and the tests you ran to -->
<!--- see how your change affects other areas of the code, etc. -->
Integration test

## Checklist:
<!--- Go over all the following points, and put an `x` in all the boxes that apply. -->
* [x] I'm merging against the `development` branch.
* [x] I have squashed my commits into a single commit.

.circleci/config.yml

@@ -124,14 +124,13 @@ commands:
       - run:
           name: Run ffi cucumber scenarios
           command: cd integration_tests && mkdir -p cucumber_output && node_modules/.bin/cucumber-js --tags "not @long-running and not @broken and not @flaky and @wallet-ffi" --format json:cucumber_output/tests-ffi.cucumber
-
       - run:
-          name: Generate report (ff)
-          command: cd integration_tests && node ./generate_report.js cucumber_output/tests-ffi.cucumber temp/reports/cucumber_ffi_report.html
+          name: Generate report (ffi)
+          command: cd integration_tests && touch cucumber_output/tests-ffi.cucumber && node ./generate_report.js cucumber_output/tests-ffi.cucumber temp/reports/cucumber_ffi_report.html
           when: always
-#      - run:
-#          name: Run flaky/broken cucumber scenarios (Always pass)
-#          command: cd integration_tests && node_modules/.bin/cucumber-js --tags "not @long-running and (@broken or @flaky)" --format json:cucumber_output/broken-tests.cucumber || true
+      #      - run:
+      #          name: Run flaky/broken cucumber scenarios (Always pass)
+      #          command: cd integration_tests && node_modules/.bin/cucumber-js --tags "not @long-running and (@broken or @flaky)" --format json:cucumber_output/broken-tests.cucumber || true
       - store_test_results:
           path: integration_tests/cucumber_output
       - store_artifacts:

integration_tests/features/BaseNodeConnectivity.feature

@@ -14,3 +14,9 @@ Feature: Base Node Connectivity
         Then I wait for WALLET_A to have 1 node connections
         Then I wait for WALLET_A to have ONLINE connectivity
         Then SEED_A is connected to WALLET_A
+
+    Scenario: Base node lists headers
+        Given I have 1 seed nodes
+        And I have a base node BN1 connected to all seed nodes
+        When I mine 5 blocks on BN1
+        Then node BN1 lists headers 1 to 5 with correct heights

integration_tests/features/support/steps.js

@@ -1088,6 +1088,20 @@ Then(/node (.*) is at tip (.*)/, async function (node, name) {
   );
 });
 
+Then(
+  /node (.*) lists headers (\d+) to (\d+) with correct heights/,
+  async function (node, start, end) {
+    const client = this.getClient(node);
+    const fromHeight = end;
+    const numHeaders = end - start + 1; // inclusive
+    const headers = await client.getHeaders(fromHeight, numHeaders);
+    const heights = headers.map((header) => parseInt(header.height));
+    for (let height = start; height <= end; height++) {
+      expect(heights).to.contain(height);
+    }
+  }
+);
+
 When(
   /I mine a block on (.*) with coinbase (.*)/,
   { timeout: 600 * 1000 },

integration_tests/helpers/baseNodeClient.js

@@ -77,6 +77,12 @@ class BaseNodeClient {
       });
   }
 
+  async getHeaders(from_height, num_headers, sorting = 0) {
+    return await this.client
+      .listHeaders()
+      .sendMessage({ from_height, num_headers, sorting });
+  }
+
   getTipHeight() {
     return this.client
       .getTipInfo()