chore(read-chunk): add tests

@vates/read-chunk/index.spec.js

@@ -0,0 +1,43 @@
+/* eslint-env jest */
+
+const { Readable } = require('stream')
+
+const { readChunk } = require('./')
+
+const makeStream = it => Readable.from(it, { objectMode: false })
+makeStream.obj = Readable.from
+
+describe('readChunk', () => {
+  it('returns null if stream is empty', async () => {
+    expect(await readChunk(makeStream([]))).toBe(null)
+  })
+
+  describe('with binary stream', () => {
+    it('returns the first chunk of data', async () => {
+      expect(await readChunk(makeStream(['foo', 'bar']))).toEqual(Buffer.from('foo'))
+    })
+
+    it('returns a chunk of the specified size (smaller than first)', async () => {
+      expect(await readChunk(makeStream(['foo', 'bar']), 2)).toEqual(Buffer.from('fo'))
+    })
+
+    it('returns a chunk of the specified size (larger than first)', async () => {
+      expect(await readChunk(makeStream(['foo', 'bar']), 4)).toEqual(Buffer.from('foob'))
+    })
+
+    it('returns less data if stream ends', async () => {
+      expect(await readChunk(makeStream(['foo', 'bar']), 10)).toEqual(Buffer.from('foobar'))
+    })
+
+    it('returns an empty buffer if the specified size is 0', async () => {
+      expect(await readChunk(makeStream(['foo', 'bar']), 0)).toEqual(Buffer.alloc(0))
+    })
+  })
+
+  describe('with object stream', () => {
+    it('returns the first chunk of data verbatim', async () => {
+      const chunks = [{}, {}]
+      expect(await readChunk(makeStream.obj(chunks))).toBe(chunks[0])
+    })
+  })
+})