diff --git a/__tests__/defineClass.test.js b/__tests__/defineClass.test.js
new file mode 100644
index 000000000..369e92f70
--- /dev/null
+++ b/__tests__/defineClass.test.js
@@ -0,0 +1,38 @@
+import postcss from 'postcss'
+import fs from 'fs'
+import _ from 'lodash'
+import defineClass from '../src/util/defineClass'
+
+let flexHelper = `.flex {
+    display: flex
+}`
+
+let inlineBlock = `.inline-block {
+    display: inline-block
+}`
+
+let inlineFlexHelper = `.inline-flex {
+    display: inline-flex
+}`
+
+let backgroundColor = `.bg-1 {
+    background-color: #bada55
+}`
+
+/**
+ * Tests
+ */
+it('creates a proper single-word class with rules', () => {
+  let output = defineClass('flex', {display: 'flex'})
+  expect(output.toString()).toEqual(flexHelper)
+})
+
+it('generates a rule with a kebab-case selector', () => {
+  let output = defineClass('inlineBlock', {display: 'inline-block'})
+  expect(output.toString()).toEqual(inlineBlock)
+})
+
+it('generates a rule with a kebab-case property name', () => {
+  let output = defineClass('bg-1', {backgroundColor: '#bada55'})
+  expect(output.toString()).toEqual(backgroundColor)
+})
diff --git a/tests/defineClasses.test.js b/__tests__/defineClasses.test.js
similarity index 53%
rename from tests/defineClasses.test.js
rename to __tests__/defineClasses.test.js
index 9481a8bfd..5e5dbdbc7 100644
--- a/tests/defineClasses.test.js
+++ b/__tests__/defineClasses.test.js
@@ -1,9 +1,9 @@
-var postcss = require('postcss')
-var fs = require('fs')
-var _ = require('lodash')
-var defineClasses = require('../src/util/defineClasses')
+import postcss from 'postcss'
+import fs from 'fs'
+import _ from 'lodash'
+import defineClasses from '../src/util/defineClasses'
 
-var config = {
+let config = {
   flex: {
     display: 'flex',
   },
@@ -12,19 +12,19 @@ var config = {
   },
 }
 
-var flexHelper = `.flex {
-  display: flex
+let flexHelper = `.flex {
+    display: flex
 }`
 
-var inlineFlexHelper = `.inline-flex {
-  display: inline-flex
+let inlineFlexHelper = `.inline-flex {
+    display: inline-flex
 }`
 
 /**
  * Tests
  */
 it('it generates a set of helper classes from a config', () => {
-  output = defineClasses(config)
+  let output = defineClasses(config)
   expect(output).toBeInstanceOf(Array)
   expect(output[0].toString()).toEqual(flexHelper)
   expect(output[1].toString()).toEqual(inlineFlexHelper)
diff --git a/package.json b/package.json
index eb02f4ee3..8a22bf782 100644
--- a/package.json
+++ b/package.json
@@ -18,6 +18,7 @@
   "devDependencies": {
     "babel-cli": "^6.6.5",
     "babel-core": "^6.7.2",
+    "babel-jest": "^20.0.3",
     "babel-loader": "^6.2.4",
     "babel-preset-env": "^1.0.0",
     "babel-preset-react": "^6.5.0",
diff --git a/tests/defineClass.test.js b/tests/defineClass.test.js
deleted file mode 100644
index 9139d4dc9..000000000
--- a/tests/defineClass.test.js
+++ /dev/null
@@ -1,38 +0,0 @@
-var postcss = require('postcss')
-var fs = require('fs')
-var _ = require('lodash')
-var defineClass = require('../src/util/defineClass')
-
-var flexHelper = `.flex {
-  display: flex
-}`
-
-var inlineBlock = `.inline-block {
-  display: inline-block
-}`
-
-var inlineFlexHelper = `.inline-flex {
-  display: inline-flex
-}`
-
-var backgroundColor = `.bg-1 {
-  background-color: #bada55
-}`
-
-/**
- * Tests
- */
-it('creates a proper single-word class with rules', () => {
-  let output = defineClass('flex', { display: 'flex' })
-  expect(output.toString()).toEqual(flexHelper)
-})
-
-it('generates a rule with a kebab-case selector', () => {
-  let output = defineClass('inlineBlock', { display: 'inline-block' })
-  expect(output.toString()).toEqual(inlineBlock)
-})
-
-it('generates a rule with a kebab-case property name', () => {
-  let output = defineClass('bg-1', { backgroundColor: '#bada55' })
-  expect(output.toString()).toEqual(backgroundColor)
-})