add first `now.json` test case

Passing.

test/_fixtures/now-json/a.js

@@ -0,0 +1 @@
+// should not be included

test/_fixtures/now-json/b.js

@@ -0,0 +1 @@
+// should be included

test/_fixtures/now-json/now.json

@@ -0,0 +1,5 @@
+{
+  "files": [
+    "b.js"
+  ]
+}

test/_fixtures/now-json/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "woot",
+  "version": "0.0.1",
+  "description": "",
+  "dependencies": {},
+  "files": [
+    "a.js"
+  ]
+}

test/index.js

@@ -165,3 +165,11 @@ test('prefix regression', async t => {
   t.is(base(files[0]), 'prefix-regression/package.json')
   t.is(base(files[1]), 'prefix-regression/woot.js')
 })
+
+test.only('support `now.json` files', async t => {
+  let files = await getNpmFiles(fixture('now-json'))
+  files = files.sort(alpha)
+  t.is(files.length, 2)
+  t.is(base(files[0]), 'now-json/b.js')
+  t.is(base(files[1]), 'now-json/package.json')
+})