added some test

Author: josestg

__example__/1.md

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+![This is a caption and image alt property](https://img.id/dog.png)
+![This thow images will be children of 'rehype-container'](https://img.id/cat.png)

__example__/2.md

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+![This is a caption and image alt property](https://img.id/dog.png)
+
+![This thow images will be children of 'rehype-container'](https://img.id/cat.png)

__example__/3.md

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+![This thow images will be children of 'rehype-container'](https://img.id/cat.png)

__example__/4.md

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+![](https://img.id/cat.png)
+
+![   ](https://img.id/cat.png)

__example__/5.md

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+# Images
+
+Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua
+
+![This is a caption and image alt property](https://img.id/dog.png)
+![This thow images will be children of 'rehype-container'](https://img.id/cat.png)
+
+Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua
+
+![This thow images will be children of 'rehype-container'](https://img.id/cat.png)

index.test.js

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+const unified = require("unified")
+const remark = require("remark-parse")
+const remark2rehype = require("remark-rehype")
+const stringify = require("rehype-stringify")
+const rehypeFigure = require("./index")
+const assert = require("assert")
+const vfile = require("to-vfile")
+
+function compile(file, opt) {
+  return unified()
+    .use(remark)
+    .use(remark2rehype)
+    .use(rehypeFigure, opt)
+    .use(stringify)
+    .processSync(vfile.readSync("./__example__/" + file))
+    .toString()
+}
+
+describe("Parse markdown to HTML", () => {
+  it("two or more images consecutively should be wrapped with 'div'.", () => {
+    const want = `<div class="rehype-figure-container"><figure class="rehype-figure"><img src="https://img.id/dog.png" alt="This is a caption and image alt property"><figcaption>This is a caption and image alt property</figcaption></figure><figure class="rehype-figure"><img src="https://img.id/cat.png" alt="This thow images will be children of &#x27;rehype-container&#x27;"><figcaption>This thow images will be children of 'rehype-container'</figcaption></figure></div>`
+    const got = compile("1.md")
+    assert.equal(want, got)
+  })
+
+  it("Should be unwrapped with 'div'.", () => {
+    const want = `<figure class="rehype-figure"><img src="https://img.id/dog.png" alt="This is a caption and image alt property"><figcaption>This is a caption and image alt property</figcaption></figure>\n<figure class="rehype-figure"><img src="https://img.id/cat.png" alt="This thow images will be children of &#x27;rehype-container&#x27;"><figcaption>This thow images will be children of 'rehype-container'</figcaption></figure>`
+    const got = compile("2.md")
+    assert.equal(want, got)
+  })
+
+  it("Custom className: Wrapped", () => {
+    const got = compile("1.md", { className: "my-className" })
+    const hasClassName = got.match(/class="my-className"/) !== null
+    const hasContainer = got.match(/class="my-className-container"/) !== null
+    assert.ok(hasClassName && hasContainer)
+  })
+
+  it("Custom className: Unwrapped", () => {
+    const got = compile("2.md", { className: "my-className" })
+    const hasClassName = got.match(/class="my-className"/) !== null
+    assert.ok(hasClassName)
+  })
+
+  it("No caption", () => {
+    const got = compile("4.md")
+    assert.ok(got.match(/<figcaption>/) === null)
+  })
+
+  it("Example", () => {
+    const got = compile("5.md")
+    const want = `<h1>Images</h1>\n<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua</p>\n<div class="rehype-figure-container"><figure class="rehype-figure"><img src="https://img.id/dog.png" alt="This is a caption and image alt property"><figcaption>This is a caption and image alt property</figcaption></figure><figure class="rehype-figure"><img src="https://img.id/cat.png" alt="This thow images will be children of &#x27;rehype-container&#x27;"><figcaption>This thow images will be children of 'rehype-container'</figcaption></figure></div>\n<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua</p>\n<figure class="rehype-figure"><img src="https://img.id/cat.png" alt="This thow images will be children of &#x27;rehype-container&#x27;"><figcaption>This thow images will be children of 'rehype-container'</figcaption></figure>`
+
+    assert.equal(got, want)
+  })
+})