Added e2e tests and snapshot files

e2e/spec/sequencediagram.spec.js

@@ -0,0 +1,35 @@
+/* eslint-env jest */
+import { imgSnapshotTest } from '../helpers/util.js'
+const { toMatchImageSnapshot } = require('jest-image-snapshot')
+
+expect.extend({ toMatchImageSnapshot })
+
+describe('Sequencediagram', () => {
+  it('should render a simple sequence diagrams', async () => {
+    await imgSnapshotTest(page, `
+      sequenceDiagram
+        participant Alice
+        participant Bob
+        participant John as John<br/>Second Line
+        Alice ->> Bob: Hello Bob, how are you?
+        Bob-->>John: How about you John?
+        Bob--x Alice: I am good thanks!
+        Bob-x John: I am good thanks!
+        Note right of John: Bob thinks a long<br/>long time, so long<br/>that the text does<br/>not fit on a row.
+        Bob-->Alice: Checking with John...
+        alt either this
+          Alice->>John: Yes
+          else or this
+          Alice->>John: No
+          else or this will happen
+          Alice->John: Maybe
+        end
+        par this happens in parallel
+        Alice -->> Bob: Parallel message 1
+        and
+        Alice -->> John: Parallel message 2
+        end
+      `,
+    {})
+  })
+})