Add tests for addStrategy

Co-authored-by: Keith Cirkel <keithamus@users.noreply.github.com>

Author: koddsson

test/lazy-define.ts

@@ -0,0 +1,34 @@
+import {expect, fixture, html} from '@open-wc/testing'
+import {spy} from 'sinon'
+import {addStrategy, lazyDefine} from '../src/lazy-define.js'
+
+describe('addStrategy', () => {
+  let strategy: ReturnType<typeof spy>
+  let promise: Promise<void>
+  let resolve: () => void
+
+  beforeEach(() => {
+    strategy = spy(() => promise = new Promise((res) => resolve = res))
+  })
+
+  it('adds a new strategy', async () => {
+    const onDefine = spy()
+    lazyDefine('foo-bar', onDefine)
+    addStrategy('test', strategy)
+    await fixture(html`<foo-bar data-load-on="test"></foo-bar>`)
+
+    expect(strategy).to.be.calledOnceWith('foo-bar')
+    expect(onDefine).to.have.callCount(0)
+    resolve()
+    await promise
+    expect(onDefine).to.be.callCount(1)
+  })
+
+  it("doesn't overwrite a existing strategy", () => {
+    expect(() => addStrategy('ready', spy())).to.throw(/already exists/)
+  })
+})
+
+describe('lazyDefine', () => {
+  it('', () => {})
+})