diff --git a/gh-badge.spec.js b/gh-badge.spec.js
index d1cc1940e9..1ae07cb352 100644
--- a/gh-badge.spec.js
+++ b/gh-badge.spec.js
@@ -1,61 +1,49 @@
-var assert = require('assert');
-var cproc = require('child_process');
-var isPng = require('is-png');
-var isSvg = require('is-svg');
+const assert = require('assert');
+const isPng = require('is-png');
+const isSvg = require('is-svg');
+const {spawn} = require('child-process-promise');
+
+function runCli (args) {
+  return spawn('node', ['gh-badge.js', ...args], { capture: ['stdout'] })
+    .then(result => result.stdout);
+}
 
 describe('The CLI', function () {
-
-  it('should provide a help message', function(done) {
-    var child = cproc.spawn('node', ['gh-badge.js']);
-    var buffer = '';
-    child.stdout.on('data', function(chunk) {
-      buffer += ''+chunk;
-    });
-    child.stdout.on('end', function() {
-      assert(buffer.startsWith('Usage'));
-      done();
+  it('should provide a help message', function () {
+    return runCli([]).then(stdout => {
+      assert(stdout.startsWith('Usage'));
     });
   });
 
-  it('should produce default badges', function(done) {
-    var child = cproc.spawn('node',
-      ['gh-badge.js', 'cactus', 'grown']);
-    child.stdout.once('data', function(chunk) {
-      var buffer = ''+chunk;
-      assert.ok(isSvg(buffer));
-      assert(buffer.includes('cactus'), 'cactus');
-      assert(buffer.includes('grown'), 'grown');
-      done();
+  it('should produce default badges', function () {
+    return runCli(['cactus', 'grown']).then(stdout => {
+      assert.ok(isSvg(stdout));
+      assert.ok(stdout.includes('cactus'), 'cactus');
+      assert.ok(stdout.includes('grown'), 'grown');
     });
   });
 
-  it('should produce colorschemed badges', function(done) {
-    var child = cproc.spawn('node',
-      ['gh-badge.js', 'cactus', 'grown', ':green']);
-    child.stdout.once('data', function(chunk) {
-      var buffer = ''+chunk;
-      assert.ok(isSvg(buffer));
-      done();
+  it('should produce colorschemed badges', function () {
+    return runCli(['cactus', 'grown', ':green']).then(stdout => {
+      assert.ok(isSvg(stdout));
     });
   });
 
-  it('should produce right-color badges', function(done) {
-    var child = cproc.spawn('node',
-      ['gh-badge.js', 'cactus', 'grown', '#abcdef']);
-    child.stdout.once('data', function(chunk) {
-      var buffer = ''+chunk;
-      assert(buffer.includes('#abcdef'), '#abcdef');
-      done();
+  it('should produce right-color badges', function () {
+    return runCli(['cactus', 'grown', '#abcdef']).then(stdout => {
+      assert.ok(isSvg(stdout));
+      assert.ok(stdout.includes('#abcdef'), '#abcdef');
     });
   });
 
-  it('should produce PNG badges', function(done) {
-    var child = cproc.spawn('node',
-      ['gh-badge.js', 'cactus', 'grown', '.png']);
-    child.stdout.once('data', function(chunk) {
-      assert.ok(isPng(chunk));
-      done();
-    });
-  });
+  it('should produce PNG badges', function () {
+    const child = runCli(['cactus', 'grown', '.png']);
 
+    // The buffering done by `child-process-promise` doesn't seem correctly to
+    // handle binary data.
+    let chunk;
+    child.childProcess.stdout.once('data', data => { chunk = data; });
+
+    return child.then(() => { assert.ok(isPng(chunk)); });
+  });
 });
diff --git a/lib/badge.spec.js b/lib/badge.spec.js
index 671ed0bbfb..d760da95d4 100644
--- a/lib/badge.spec.js
+++ b/lib/badge.spec.js
@@ -1,10 +1,9 @@
 const assert = require('assert');
+const badge = require('./badge');
 const isSvg = require('is-svg');
 
-const badge = require('./badge');
-
 describe('The badge generator', function () {
-  it('should produce SVG', function(done) {
+  it('should produce SVG', function (done) {
     badge({ text: ['cactus', 'grown'], format: 'svg' }, svg => {
       assert.ok(isSvg(svg));
       assert(svg.includes('cactus'), 'cactus');
diff --git a/lib/lru-cache.spec.js b/lib/lru-cache.spec.js
index a404703a20..61e8cfba3e 100644
--- a/lib/lru-cache.spec.js
+++ b/lib/lru-cache.spec.js
@@ -1,22 +1,20 @@
-var assert = require('assert');
-
-var LRU = require('./lru-cache');
+const assert = require('assert');
+const LRU = require('./lru-cache');
 
 describe('The LRU cache', function () {
-
-  it("should support being called without new", function() {
-    var cache = LRU(1);
+  it('should support being called without new', function () {
+    const cache = LRU(1);
     assert(cache instanceof LRU);
   });
 
-  it("should support a zero capacity", function() {
-    var cache = new LRU(0);
+  it('should support a zero capacity', function () {
+    const cache = new LRU(0);
     cache.set('key', 'value');
     assert.equal(cache.cache.size, 0);
   });
 
-  it("should support a one capacity", function() {
-    var cache = new LRU(1);
+  it('should support a one capacity', function () {
+    const cache = new LRU(1);
     cache.set('key1', 'value1');
     assert.equal(cache.cache.size, 1);
     assert.equal(cache.newest, cache.cache.get('key1'));
@@ -29,14 +27,14 @@ describe('The LRU cache', function () {
     assert.equal(cache.get('key2'), 'value2');
   });
 
-  it("should remove the oldest element when reaching capacity", function() {
-    var cache = new LRU(2);
+  it('should remove the oldest element when reaching capacity', function () {
+    const cache = new LRU(2);
     cache.set('key1', 'value1');
     cache.set('key2', 'value2');
     cache.set('key3', 'value3');
     cache.cache.get('key1');
-    var slot2 = cache.cache.get('key2');
-    var slot3 = cache.cache.get('key3');
+    const slot2 = cache.cache.get('key2');
+    const slot3 = cache.cache.get('key3');
     assert.equal(cache.cache.size, 2);
     assert.equal(cache.oldest, slot2);
     assert.equal(cache.newest, slot3);
@@ -50,8 +48,8 @@ describe('The LRU cache', function () {
     assert.equal(cache.get('key3'), 'value3');
   });
 
-  it("should make sure that resetting a key in cache makes it newest", function() {
-    var cache = new LRU(2);
+  it('should make sure that resetting a key in cache makes it newest', function () {
+    const cache = new LRU(2);
     cache.set('key', 'value');
     cache.set('key2', 'value2');
     assert.equal(cache.oldest, cache.cache.get('key'));
@@ -61,11 +59,11 @@ describe('The LRU cache', function () {
     assert.equal(cache.newest, cache.cache.get('key'));
   });
 
-  it("should make sure that getting a key in cache makes it newest", function() {
-    var slot1, slot2, slot3;
+  it('should make sure that getting a key in cache makes it newest', function () {
+    let slot1, slot2, slot3, cache;
 
     // When the key is oldest.
-    var cache = new LRU(2);
+    cache = new LRU(2);
     cache.set('key1', 'value1');
     cache.set('key2', 'value2');
     slot1 = cache.cache.get('key1');
diff --git a/lib/svg-to-img.spec.js b/lib/svg-to-img.spec.js
index 1e2b089b43..7528f6d95b 100644
--- a/lib/svg-to-img.spec.js
+++ b/lib/svg-to-img.spec.js
@@ -1,8 +1,7 @@
 const assert = require('assert');
-const sinon = require('sinon');
-const isPng = require('is-png');
-
 const badge = require('./badge');
+const isPng = require('is-png');
+const sinon = require('sinon');
 const svg2img = require('./svg-to-img');
 
 describe('The rasterizer', function () {
diff --git a/package.json b/package.json
index 59902ca5ca..4f227e312b 100644
--- a/package.json
+++ b/package.json
@@ -62,6 +62,7 @@
     "logo"
   ],
   "devDependencies": {
+    "child-process-promise": "^2.2.1",
     "eslint": "^3.18.0",
     "glob": "^7.1.1",
     "icedfrisby": "^1.1.0",
diff --git a/server.spec.js b/server.spec.js
index 3ba5f0a74c..1a357cdaeb 100644
--- a/server.spec.js
+++ b/server.spec.js
@@ -1,18 +1,17 @@
-var assert = require('assert');
-var sinon = require('sinon');
-var http = require('http');
-var fs = require('fs');
-var path = require('path');
-var isPng = require('is-png');
-var isSvg = require('is-svg');
+const assert = require('assert');
+const config = require('./lib/test-config');
 const fetch = require('node-fetch');
-var svg2img = require('./lib/svg-to-img');
+const fs = require('fs');
+const isPng = require('is-png');
+const isSvg = require('is-svg');
+const path = require('path');
 const serverHelpers = require('./lib/in-process-server-test-helpers');
-
-var port = '1111';
-var url = 'http://127.0.0.1:' + port + '/';
+const sinon = require('sinon');
+const svg2img = require('./lib/svg-to-img');
 
 describe('The server', function () {
+  const baseUri = `http://127.0.0.1:${config.port}`;
+
   let server;
   before('Start running the server', function () {
     this.timeout(5000);
@@ -20,61 +19,55 @@ describe('The server', function () {
   });
   after('Shut down the server', function () { serverHelpers.stop(server); });
 
-  it('should produce colorscheme badges', function(done) {
-    http.get(url + ':fruit-apple-green.svg',
-      function(res) {
-        var buffer = '';
-        res.on('data', function(chunk) { buffer += ''+chunk; });
-        res.on('end', function() {
-          assert.ok(isSvg(buffer));
-          assert(buffer.includes('fruit'), 'fruit');
-          assert(buffer.includes('apple'), 'apple');
-          done();
-        });
-    });
+  it('should produce colorscheme badges', function () {
+    return fetch(`${baseUri}/:fruit-apple-green.svg`)
+      .then(res => {
+        assert.ok(res.ok);
+        return res.text();
+      }).then(text => {
+        assert.ok(isSvg(text));
+        assert(text.includes('fruit'), 'fruit');
+        assert(text.includes('apple'), 'apple');
+      });
   });
 
-  it('should produce colorscheme PNG badges', function(done) {
-    http.get(url + ':fruit-apple-green.png',
-      function(res) {
-        res.once('data', function(chunk) {
-          assert.ok(isPng(chunk));
-          done();
-        });
-    });
+  it('should produce colorscheme PNG badges', function () {
+    return fetch(`${baseUri}/:fruit-apple-green.png`)
+      .then(res => {
+        assert.ok(res.ok);
+        return res.buffer();
+      }).then(data => {
+        assert.ok(isPng(data));
+      });
   });
 
   context('with svg2img error', function () {
-    var expectedError = fs.readFileSync(path.resolve(__dirname, 'public', '500.html'));
+    const expectedError = fs.readFileSync(path.resolve(__dirname, 'public', '500.html'));
 
-    var toBufferStub;
+    let toBufferStub;
     beforeEach(function () {
       toBufferStub = sinon.stub(svg2img._imageMagick.prototype, 'toBuffer')
         .callsArgWith(1, Error('whoops'));
     });
     afterEach(function () { toBufferStub.restore(); });
 
-    it('should emit the 500 message', function (done) {
-      http.get(url + ':some_new-badge-green.png',
-        function(res) {
+    it('should emit the 500 message', function () {
+      return fetch(`${baseUri}/:some_new-badge-green.png`)
+        .then(res => {
           // This emits status code 200, though 500 would be preferable.
-          assert.equal(res.statusCode, 200);
-
-          var buffer = '';
-          res.on('data', function(chunk) { buffer += ''+chunk; });
-          res.on('end', function() {
-            assert.equal(buffer, expectedError);
-            done();
-          });
-      });
+          assert.equal(res.status, 200);
+          return res.text();
+        }).then(text => {
+          assert.equal(text, expectedError);
+        });
     });
   });
 
   describe('analytics endpoint', function () {
     it('should return analytics in the expected format', function () {
-      return fetch(`${url}$analytics/v1`)
+      return fetch(`${baseUri}/$analytics/v1`)
         .then(res => {
-          assert(res.ok);
+          assert.ok(res.ok);
           return res.json();
         }).then(json => {
           const keys = Object.keys(json);