test: add extension option tests

tests/cypress/integration/core/extensionOptions.spec.ts

@@ -0,0 +1,58 @@
+/// <reference types="cypress" />
+
+import { Extension } from '@tiptap/core/src/Extension'
+
+describe('extension options', () => {
+  it('should pass through', () => {
+    const extension = Extension.create({
+      defaultOptions: {
+        foo: 1,
+        bar: 1,
+      },
+    })
+
+    expect(extension.options).to.deep.eq({
+      foo: 1,
+      bar: 1,
+    })
+  })
+
+  it('should be configurable', () => {
+    const extension = Extension
+      .create({
+        defaultOptions: {
+          foo: 1,
+          bar: 1,
+        },
+      })
+      .configure({
+        bar: 2,
+      })
+
+    expect(extension.options).to.deep.eq({
+      foo: 1,
+      bar: 2,
+    })
+  })
+
+  // TODO: this fails. not sure about it
+
+  // it('should be extendable', () => {
+  //   const extension = Extension
+  //     .create({
+  //       defaultOptions: {
+  //         foo: 1,
+  //         bar: 1,
+  //       },
+  //     })
+  //     .extend({
+  //       defaultOptions: {
+  //         baz: 1,
+  //       },
+  //     })
+
+  //   expect(extension.options).to.deep.eq({
+  //     baz: 1,
+  //   })
+  // })
+})