test: improve test coverage for DataProviderController (#7546)

packages/component-base/test/data-provider-controller-cache.test.js

@@ -1,6 +1,8 @@
 import { expect } from '@esm-bundle/chai';
 import { Cache } from '../src/data-provider-controller/cache.js';
 
+const PLACEHOLDER = Symbol('PLACEHOLDER');
+
 describe('DataProviderController - Cache', () => {
   let cache;
   let expandedItems = [];
@@ -51,23 +53,42 @@ describe('DataProviderController - Cache', () => {
     });
   });
 
+  describe('with placeholder', () => {
+    beforeEach(() => {
+      cache = new Cache({ isExpanded, placeholder: PLACEHOLDER }, 2, 20);
+    });
+
+    it('should have items filled with placeholders', () => {
+      expect(cache.items).to.have.lengthOf(20);
+      expect(cache.items.every((item) => item === PLACEHOLDER)).to.be.true;
+    });
+  });
+
   describe('setPage', () => {
     beforeEach(() => {
-      cache = new Cache({ isExpanded }, 50, 500);
+      cache = new Cache({ isExpanded }, 2, 20);
     });
 
-    it('should insert the items at the correct position for page 0', () => {
+    it('should insert items at the correct position for page 0', () => {
       cache.setPage(0, ['Item 0', 'Item 1']);
       expect(cache.items).to.have.lengthOf(2);
       expect(cache.items[0]).to.equal('Item 0');
       expect(cache.items[1]).to.equal('Item 1');
     });
 
-    it('should insert the items at the correct position for page 1', () => {
-      cache.setPage(1, ['Item 0', 'Item 1']);
-      expect(cache.items).to.have.lengthOf(52);
-      expect(cache.items[50]).to.equal('Item 0');
-      expect(cache.items[51]).to.equal('Item 1');
+    it('should insert items at the correct position for page 1', () => {
+      cache.setPage(1, ['Item 2', 'Item 3']);
+      expect(cache.items).to.have.lengthOf(4);
+      expect(cache.items[2]).to.equal('Item 2');
+      expect(cache.items[3]).to.equal('Item 3');
+    });
+
+    it('should discard items that exceed the size bounds', () => {
+      cache.setPage(9, ['Item 18', 'Item 19', 'Item 20']);
+      expect(cache.items).to.have.lengthOf(20);
+      expect(cache.items[18]).to.equal('Item 18');
+      expect(cache.items[19]).to.equal('Item 19');
+      expect(cache.items[20]).to.be.undefined;
     });
   });
 
@@ -197,6 +218,38 @@ describe('DataProviderController - Cache', () => {
     });
   });
 
+  describe('size', () => {
+    beforeEach(() => {
+      cache = new Cache({ isExpanded }, 2, 20);
+    });
+
+    it('should remove exceeding pending requests when decreasing size', () => {
+      cache.pendingRequests[8] = (_items, _size) => {};
+      cache.pendingRequests[9] = (_items, _size) => {};
+      cache.size = 18;
+      expect(cache.pendingRequests[8]).to.be.not.undefined;
+      expect(cache.pendingRequests[9]).to.be.undefined;
+    });
+  });
+
+  describe('size with placeholder', () => {
+    beforeEach(() => {
+      cache = new Cache({ isExpanded, placeholder: PLACEHOLDER }, 2, 20);
+    });
+
+    it('should add more placeholders when increasing size', () => {
+      cache.size = 22;
+      expect(cache.items).to.have.lengthOf(22);
+      expect(cache.items.every((item) => item === PLACEHOLDER)).to.be.true;
+    });
+
+    it('should remove exceeding placeholders when decreasing size', () => {
+      cache.size = 18;
+      expect(cache.items).to.have.lengthOf(18);
+      expect(cache.items.every((item) => item === PLACEHOLDER)).to.be.true;
+    });
+  });
+
   describe('flatSize', () => {
     beforeEach(() => {
       cache = new Cache({ isExpanded }, 50, 500);

packages/component-base/test/data-provider-controller-placeholder.test.js

@@ -0,0 +1,85 @@
+import { expect } from '@esm-bundle/chai';
+import sinon from 'sinon';
+import '@vaadin/testing-helpers';
+import { DataProviderController } from '../src/data-provider-controller/data-provider-controller.js';
+import { createDataProvider } from './data-provider-controller-helpers.js';
+
+class Placeholder {}
+
+class CustomPlaceholder extends Placeholder {}
+
+describe('DataProviderController - placeholder', () => {
+  let host, controller, placeholder, dataProviderSpy;
+
+  describe('default', () => {
+    beforeEach(() => {
+      host = document.createElement('div');
+
+      placeholder = new Placeholder();
+
+      controller = new DataProviderController(host, {
+        size: 10,
+        pageSize: 2,
+        placeholder,
+        dataProvider: createDataProvider({ size: 10, async: true }),
+      });
+
+      dataProviderSpy = sinon.spy(controller, 'dataProvider');
+    });
+
+    it('should have placeholder', () => {
+      expect(controller.placeholder).to.equal(placeholder);
+    });
+
+    it('should have rootCache items filled with placeholders', () => {
+      expect(controller.rootCache.items).to.have.lengthOf(10);
+      expect(controller.rootCache.items.every((item) => item === placeholder)).to.be.true;
+    });
+
+    it('should request data when encountering the controller placeholder instance', () => {
+      controller.ensureFlatIndexLoaded(0);
+      expect(dataProviderSpy).to.have.callCount(1);
+
+      controller.ensureFlatIndexLoaded(1);
+      expect(dataProviderSpy).to.have.callCount(1);
+
+      controller.ensureFlatIndexLoaded(2);
+      expect(dataProviderSpy).to.have.callCount(2);
+
+      controller.ensureFlatIndexLoaded(3);
+      expect(dataProviderSpy).to.have.callCount(2);
+    });
+
+    it('should not request data when encountering a different placeholder instance', () => {
+      controller.rootCache.items[0] = new CustomPlaceholder();
+      controller.ensureFlatIndexLoaded(0);
+      expect(dataProviderSpy).to.have.callCount(0);
+    });
+  });
+
+  describe('custom equality function', () => {
+    beforeEach(() => {
+      host = document.createElement('div');
+
+      controller = new DataProviderController(host, {
+        size: 10,
+        pageSize: 2,
+        placeholder: new Placeholder(),
+        isPlaceholder: (item) => item instanceof Placeholder,
+        dataProvider: createDataProvider({ size: 10, async: true }),
+      });
+
+      dataProviderSpy = sinon.spy(controller, 'dataProvider');
+    });
+
+    it('should request data when encountering any placeholder instance', () => {
+      controller.rootCache.items[0] = new CustomPlaceholder();
+
+      controller.ensureFlatIndexLoaded(0);
+      expect(dataProviderSpy).to.have.callCount(1);
+
+      controller.ensureFlatIndexLoaded(2);
+      expect(dataProviderSpy).to.have.callCount(2);
+    });
+  });
+});

packages/component-base/test/data-provider-controller.test.js

@@ -5,6 +5,8 @@ import { Cache } from '../src/data-provider-controller/cache.js';
 import { DataProviderController } from '../src/data-provider-controller/data-provider-controller.js';
 import { createDataProvider } from './data-provider-controller-helpers.js';
 
+const PLACEHOLDER = Symbol('PLACEHOLDER');
+
 describe('DataProviderController', () => {
   let host, controller;
 
@@ -47,10 +49,22 @@ describe('DataProviderController', () => {
       expect(controller.flatSize).to.equal(0);
     });
 
+    it('should not have placeholder', () => {
+      expect(controller.placeholder).to.be.undefined;
+    });
+
+    it('should not have isPlaceholder', () => {
+      expect(controller.isPlaceholder).to.be.undefined;
+    });
+
     it('should have rootCache', () => {
       expect(controller.rootCache).to.be.instanceOf(Cache);
     });
 
+    it('should have empty rootCache items', () => {
+      expect(controller.rootCache.items).to.have.lengthOf(0);
+    });
+
     it('should not have rootCache size', () => {
       expect(controller.rootCache.size).to.be.undefined;
     });
@@ -85,6 +99,10 @@ describe('DataProviderController', () => {
     it('should have rootCache size', () => {
       expect(controller.rootCache.size).to.equal(500);
     });
+
+    it('should have empty rootCache items', () => {
+      expect(controller.rootCache.items).to.have.lengthOf(0);
+    });
   });
 
   describe('with dataProviderParams', () => {