test(table): add tests for MatTableDataSource (#18767)

* test(table): add tests for MatTableDataSource

* switch shuffle to reverse

Author: andrewseguin

src/material/table/table-data-source.spec.ts

@@ -0,0 +1,58 @@
+import {MatTableDataSource} from './table-data-source';
+import {async, ComponentFixture, TestBed} from '@angular/core/testing';
+import {MatSort, MatSortModule} from '@angular/material/sort';
+import {NoopAnimationsModule} from '@angular/platform-browser/animations';
+import {Component, ViewChild} from '@angular/core';
+
+describe('MatTableDataSource', () => {
+  const dataSource = new MatTableDataSource();
+
+  beforeEach(async(() => {
+    TestBed.configureTestingModule({
+      imports: [MatSortModule, NoopAnimationsModule],
+      declarations: [MatSortApp],
+    }).compileComponents();
+  }));
+
+  describe('sort', () => {
+    let fixture: ComponentFixture<MatSortApp>;
+    let sort: MatSort;
+
+    beforeEach(() => {
+      fixture = TestBed.createComponent(MatSortApp);
+      sort = fixture.componentInstance.sort;
+      fixture.detectChanges();
+    });
+
+    /** Test the data source's `sortData` function. */
+    function testSortWithValues(values: any[]) {
+      // The data source and MatSort expect the list to contain objects with values, where
+      // the sort should be performed over a particular key.
+      // Map the values into an array of objects where where each value is keyed by "prop"
+      // e.g. [0, 1, 2] -> [{prop: 0}, {prop: 1}, {prop: 2}]
+      const data = values.map(v => ({'prop': v}));
+
+      // Set the active sort to be on the "prop" key
+      sort.active = 'prop';
+
+      const reversedData = data.slice().reverse();
+      const sortedData = dataSource.sortData(reversedData, sort);
+      expect(sortedData).toEqual(data);
+    }
+
+    it('should be able to correctly sort an array of numbers', () => {
+      testSortWithValues([-2, -1, 0, 1, 2]);
+    });
+
+    it('should be able to correctly sort an array of string', () => {
+      testSortWithValues(['apples', 'bananas', 'cherries', 'lemons', 'strawberries']);
+    });
+  });
+});
+
+@Component({
+  template: `<div matSort matSortDirection="asc"></div>`
+})
+class MatSortApp {
+  @ViewChild(MatSort, {static: true}) sort: MatSort;
+}