From cb1c4b8afe832cf86298c6a6b11d33f97fa73516 Mon Sep 17 00:00:00 2001
From: Eric Hwang <eric.hwang@lever.co>
Date: Fri, 21 May 2021 17:50:46 -0500
Subject: [PATCH] test-utils `.to.render` assertion - Reset page/component
 state between each render pass

---
 test-utils/assertions.js           | 22 ++++++++++++++++++++--
 test/dom/ComponentHarness.mocha.js | 25 +++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/test-utils/assertions.js b/test-utils/assertions.js
index 080ed496..d5d20ec3 100644
--- a/test-utils/assertions.js
+++ b/test-utils/assertions.js
@@ -41,6 +41,20 @@ module.exports = function(dom, Assertion) {
     return el.innerHTML;
   }
 
+  // Executes the parts of `Page#destroy` pertaining to the model, which get
+  // re-done when a new Page gets created on the same model. Normally, using
+  // `Page#destroy` would be fine, but the `.to.render` assertion wants to do
+  // 3 rendering passes on the same data, so we can't completely clear the
+  // model's state between the rendering passes.
+  function resetPageModel(page) {
+    page._removeModelListeners();
+    for (var componentId in page._components) {
+      var component = page._components[componentId];
+      component.destroy();
+    }
+    page.model.silent().destroy('$components');
+  }
+
   if (Assertion) {
     Assertion.addMethod('html', function(expected, options) {
       var obj = this._obj;
@@ -76,7 +90,8 @@ module.exports = function(dom, Assertion) {
       new Assertion(harness).instanceOf(ComponentHarness);
 
       // Render to a HTML string.
-      var htmlString = harness.renderHtml(options).html;
+      var renderResult = harness.renderHtml(options);
+      var htmlString = renderResult.html;
 
       // Normalize `htmlString` into the same form as the DOM would give for `element.innerHTML`.
       //
@@ -105,6 +120,8 @@ module.exports = function(dom, Assertion) {
         }
       }
 
+      resetPageModel(renderResult.page);
+
       // Check DOM rendering is also equivalent.
       // This uses the harness "pageRendered" event to grab the rendered DOM *before* any component
       // `create()` methods are called, as `create()` methods can do DOM mutations.
@@ -121,7 +138,8 @@ module.exports = function(dom, Assertion) {
           }
         }
       });
-      harness.renderDom(options);
+      renderResult = harness.renderDom(options);
+      resetPageModel(renderResult.page);
 
       // Try attaching. Attachment will throw an error if HTML doesn't match
       var el = domDocument.createElement(parentTag);
diff --git a/test/dom/ComponentHarness.mocha.js b/test/dom/ComponentHarness.mocha.js
index 5d04409f..69376d9d 100644
--- a/test/dom/ComponentHarness.mocha.js
+++ b/test/dom/ComponentHarness.mocha.js
@@ -215,6 +215,31 @@ describe('ComponentHarness', function() {
       expect(harness).to.render();
       expect(harness).to.render('&lt;&nbsp;"&gt;');
     });
+
+    it('cleans up component state between render passes', function() {
+      function Box() {}
+      Box.view = {
+        is: 'box',
+        source: '<index:><div class="box">{{greeting}}</div>'
+      };
+      Box.prototype.init = function() {
+        var initialName = this.model.scope('_page.initialName').get();
+        expect(initialName).to.equal('Spot');
+        this.model.set('name', initialName);
+        this.model.start('greeting', ['name'], function(name) {
+          // This assertion ensures that the reactive function isn't called after
+          // the component gets destroyed.
+          expect(name).to.equal('Spot');
+          return 'Hello, ' + name;
+        });
+      };
+      var harness = runner.createHarness('<view is="box" />', Box);
+      // Have the test depend on state in `_page` to make sure it's not cleared
+      // between rendering passes in `.to.render`.
+      harness.model.set('_page.initialName', 'Spot');
+
+      expect(harness).to.render('<div class="box">Hello, Spot</div>');
+    });
   });
 
   describe('fake app.history implementation', function() {