Add e2e tests for slButton

test/e2e/button.e2e.ts

@@ -0,0 +1,67 @@
+import { newE2EPage } from '@stencil/core/testing';
+
+const testContent = `
+<sl-button>Button</sl-button>
+<button>Other Element</button>
+`;
+
+describe('button', () => {
+  it('should emit slFocus when gaining focus', async () => {
+    const page = await newE2EPage();
+    await page.setContent(testContent);
+
+    const button = await page.find('sl-button');
+
+    const slFocus = await button.spyOnEvent('slFocus');
+
+    // give focus
+    await button.click();
+
+    expect(slFocus).toHaveReceivedEventTimes(1);
+  });
+
+  it('should emit slBlur when losing focus', async () => {
+    const page = await newE2EPage();
+    await page.setContent(testContent);
+
+    const button = await page.find('sl-button');
+    const otherElement = await page.find('button');
+
+    const slFocus = await button.spyOnEvent('slBlur');
+
+    //give focus
+    await button.click();
+
+    // remove focus by clicking on other element
+    await otherElement.click();
+
+    expect(slFocus).toHaveReceivedEventTimes(1);
+  });
+
+  it('should emit slFocus on setFocus', async () => {
+    const page = await newE2EPage();
+    await page.setContent(testContent);
+
+    const button = await page.find('sl-button');
+
+    const slFocus = await button.spyOnEvent('slFocus');
+
+    await button.callMethod('setFocus');
+
+    expect(slFocus).toHaveReceivedEventTimes(1);
+  });
+
+  it('should emit slBlur on removeFocus', async () => {
+    const page = await newE2EPage();
+    await page.setContent(testContent);
+
+    const button = await page.find('sl-button');
+
+    const slBlur = await button.spyOnEvent('slBlur');
+
+    await button.callMethod('setFocus');
+    await button.callMethod('removeFocus');
+
+    expect(slBlur).toHaveReceivedEventTimes(1);
+  });
+});