chore(gatsby-plugin-twitter): Add pluginOptionsSchema validation

packages/gatsby-plugin-twitter/package.json

@@ -13,7 +13,8 @@
     "@babel/cli": "^7.11.6",
     "@babel/core": "^7.11.6",
     "babel-preset-gatsby-package": "^0.6.0-next.0",
-    "cross-env": "^7.0.2"
+    "cross-env": "^7.0.2",
+    "gatsby-plugin-utils": "^0.3.0-next.0"
   },
   "homepage": "https://github.com/gatsbyjs/gatsby/tree/master/packages/gatsby-plugin-twitter#readme",
   "keywords": [

packages/gatsby-plugin-twitter/src/__tests__/gatsby-node.js

@@ -0,0 +1,26 @@
+import { testPluginOptionsSchema } from "gatsby-plugin-utils"
+
+import { pluginOptionsSchema } from "../gatsby-node"
+
+it(`should provide meaningful errors when fields are invalid`, async () => {
+  const expectedErrors = [`"optionA" is not allowed`]
+
+  const { errors } = await testPluginOptionsSchema(pluginOptionsSchema, {
+    optionA: `This options shouldn't exist`,
+  })
+
+  expect(errors).toEqual(expectedErrors)
+})
+
+it.each`
+  options
+  ${undefined}
+  ${{}}
+`(`should validate the schema: $options`, async ({ options }) => {
+  const { isValid } = await testPluginOptionsSchema(
+    pluginOptionsSchema,
+    options
+  )
+
+  expect(isValid).toBe(true)
+})

packages/gatsby-plugin-twitter/src/gatsby-node.js

@@ -0,0 +1 @@
+exports.pluginOptionsSchema = ({ Joi }) => Joi.object({})