diff --git a/.travis.yml b/.travis.yml
index 7964c50da..2303d5e71 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,7 +8,7 @@ jobs:
       name: 'Linting'
       script: npm run lint
     - name: 'Coverage'
-      script: npm run coverage && npm run coveralls
+      script: npm run coverage-coveralls
     - stage: release
       if: branch = master
       script: skip
diff --git a/package.json b/package.json
index 76de9805e..ad656b50a 100644
--- a/package.json
+++ b/package.json
@@ -7,11 +7,11 @@
   "browser": "dist/liquid.js",
   "scripts": {
     "lint": "eslint . --ext .ts --ext .js",
-    "unit": "mocha -r ts-node/register -r tsconfig-paths/register test/unit/**.ts",
-    "e2e": "npm run build && mocha -r ts-node/register -r tsconfig-paths/register test/e2e/**/*.ts",
+    "unit": "mocha test/unit/*.ts test/unit/**/*.ts",
+    "e2e": "npm run build && mocha test/e2e/**/*.ts test/e2e/*.ts",
     "test": "npm run unit && npm run e2e",
-    "coverage": "nyc --reporter=html npm run unit",
-    "coveralls": "nyc report --reporter=text-lcov | coveralls",
+    "coverage-html": "nyc npm run unit && nyc report --reporter=html",
+    "coverage-coveralls": "nyc npm run unit && nyc report --reporter=text-lcov | coveralls",
     "build": "rollup -c && ls -lh dist",
     "version": "npm run build && git add -A dist"
   },
@@ -68,6 +68,7 @@
     "semantic-release": "^15.13.3",
     "sinon": "^7.2.3",
     "sinon-chai": "^3.3.0",
+    "source-map-support": "^0.5.10",
     "supertest": "^3.4.2",
     "ts-node": "^8.0.2",
     "tsconfig-paths": "^3.8.0",
@@ -82,5 +83,8 @@
       "@semantic-release/npm",
       "@semantic-release/git"
     ]
+  },
+  "nyc": {
+    "extension": [ ".ts" ]
   }
 }
diff --git a/src/parser/template.ts b/src/parser/template.ts
index 360aec844..ef0d4ff7b 100644
--- a/src/parser/template.ts
+++ b/src/parser/template.ts
@@ -1,10 +1,12 @@
 import * as _ from '../util/underscore'
 import * as path from 'path'
 import { anySeries } from '../util/promise'
-import * as fs from 'fs'
+import { stat, readFile } from 'fs'
 
-const statFileAsync = <(filepath: string) => Promise<object>>_.promisify(fs.stat)
-const readFileAsync = <(filepath: string, encoding: string) => Promise<string>>_.promisify(fs.readFile)
+export const fs = {
+  stat: _.promisify(stat) as ((filepath: string) => Promise<object>),
+  readFile: _.promisify(readFile) as ((filepath: string, encoding: string) => Promise<string>)
+}
 
 export async function resolve (filepath, root, options) {
   if (!path.extname(filepath)) {
@@ -15,7 +17,7 @@ export async function resolve (filepath, root, options) {
   const paths = root.map(root => path.resolve(root, filepath))
   return anySeries(paths, async path => {
     try {
-      await statFileAsync(path)
+      await fs.stat(path)
       return path
     } catch (e) {
       e.message = `${e.code}: Failed to lookup ${filepath} in: ${root}`
@@ -25,5 +27,5 @@ export async function resolve (filepath, root, options) {
 }
 
 export async function read (filepath): Promise<string> {
-  return readFileAsync(filepath, 'utf8')
+  return fs.readFile(filepath, 'utf8')
 }
diff --git a/test/mocha.opts b/test/mocha.opts
new file mode 100644
index 000000000..bdc416ac0
--- /dev/null
+++ b/test/mocha.opts
@@ -0,0 +1,2 @@
+--require ts-node/register
+--require tsconfig-paths/register 
diff --git a/test/unit/options/trimming.ts b/test/unit/options/trimming.ts
index 899aced70..63666c4be 100644
--- a/test/unit/options/trimming.ts
+++ b/test/unit/options/trimming.ts
@@ -12,7 +12,7 @@ describe('LiquidOptions#trimming', function () {
     })
     it('should respect trim_tag_right', async function () {
       const engine = new Liquid({ trim_tag_right: true })
-      const html = engine.parseAndRender('\t{%if true%}foo{%endif%} \n')
+      const html = await engine.parseAndRender('\t{%if true%}foo{%endif%} \n')
       return expect(html).to.equal('\tfoo')
     })
     it('should not trim value', async function () {
diff --git a/test/unit/template.ts b/test/unit/template.ts
index 146549a07..e894116ab 100644
--- a/test/unit/template.ts
+++ b/test/unit/template.ts
@@ -1,13 +1,28 @@
 import { resolve } from '../../src/parser/template'
-import * as mock from 'mock-fs'
-import { expect } from 'chai'
 import * as path from 'path'
+import { fs } from 'src/parser/template'
+import { expect, use } from 'chai'
+import * as chaiAsPromised from 'chai-as-promised'
+
+use(chaiAsPromised)
 
 describe('template', function () {
+  let readFile, stat
   before(function () {
-    mock({
-      '/foo/bar.html': 'bar'
-    })
+    readFile = fs.readFile
+    stat = fs.stat
+    fs.readFile = async function (file) {
+      if (file === '/foo/bar.html') return 'bar'
+      throw new Error('NOENT')
+    }
+    fs.stat = async function (file) {
+      if (file === '/foo/bar.html') return { type: 'file' }
+      throw new Error('NOENT')
+    }
+  })
+  after(function () {
+    fs.readFile = readFile
+    fs.stat = stat
   })
   describe('#resolve()', function () {
     it('should resolve based on root', async function () {
diff --git a/test/unit/util/error.ts b/test/unit/util/error.ts
index fc065475e..96fdb2a11 100644
--- a/test/unit/util/error.ts
+++ b/test/unit/util/error.ts
@@ -47,7 +47,8 @@ describe('error', function () {
     it('should contain stack in err.stack', async function () {
       const err = await expect(engine.parseAndRender('{% . a %}')).be.rejected
       expect(err.message).to.contain('illegal tag syntax')
-      expect(err.stack).to.contain('at Object.parse')
+      console.log(err.stack)
+      expect(err.stack).to.contain('at Liquid.parse')
     })
     describe('captureStackTrace compatibility', function () {
       const captureStackTrace = Error.captureStackTrace
diff --git a/test/unit/util/promise.ts b/test/unit/util/promise.ts
index 1c551a99f..8747abb69 100644
--- a/test/unit/util/promise.ts
+++ b/test/unit/util/promise.ts
@@ -52,9 +52,9 @@ describe('util/promise', function () {
         .then(() => expect(spy).to.not.have.been.called)
     })
   })
-  describe('.mapSeries()', function () {
+  describe('.mapSeries()', async function () {
     it('should resolve when all resolved', async function () {
-      const result = P.mapSeries(
+      const result = await P.mapSeries(
         ['first', 'second', 'third'],
         item => Promise.resolve(item)
       )