Tools: Added hook to allow tearing down non-atomic visual tests

test/karma-conf.js

@@ -666,6 +666,14 @@ module.exports = function (config) {
 function createVisualTestTemplate(argv, path, js, assertion) {
     let scriptBody = resolveJSON(js);
 
+    let afterEach = 'undefined';
+    if (fs.existsSync(`samples/${path}/aftereach.js`)) {
+        afterEach = fs.readFileSync(`samples/${path}/aftereach.js`, 'utf8');
+        afterEach = `function () {
+            ${afterEach}
+        }`;
+    }
+
     // Don't do intervals (typically for gauge samples, add point etc)
     scriptBody = scriptBody.replace('setInterval', 'Highcharts.noop');
 
@@ -719,6 +727,7 @@ function createVisualTestTemplate(argv, path, js, assertion) {
                         done();
                     `}
                     assert.test.resets = ${resets};
+                    assert.test.sampleAfterEach = ${afterEach};
                 } else if (attempts < 50) {
                     setTimeout(waitForChartToLoad, 100);
                     attempts++;
@@ -729,6 +738,7 @@ function createVisualTestTemplate(argv, path, js, assertion) {
                     );
                     done();
                     assert.test.resets = ${resets};
+                    assert.test.sampleAfterEach = ${afterEach};
                 }
             }
             waitForChartToLoad();

test/karma-setup.js

@@ -246,6 +246,10 @@ if (window.QUnit) {
             }
             Highcharts.wrap = origWrap;
 
+            if (typeof test.test.sampleAfterEach === 'function') {
+                test.test.sampleAfterEach();
+            }
+
             // Reset defaultOptions and callbacks if those are mutated. In
             // karma-konf, the scriptBody is inspected to see if these expensive
             // operations are necessary. Visual tests only.

test/readme.md

@@ -55,6 +55,10 @@ limit the number of charts in the test suite.
 - All the tests run on one Highcharts instance. When running
   `Highcharts.setOptions()`, make sure to unset the changed options, otherwise
   it may break tests downstream.
+- In visual tests, `plotOptions` and `callbacks` are reset after each test. If
+  other properties of Highcharts are mutated, a file `aftereach.js` can be added
+  to reset them. Since the visual tests double as educational demos for the
+  public, it is not recommended to have teardown code in `demo.js`.
 
 #### Link References
 - Highchars Utils: https://github.com/highcharts/highcharts-utils