diff --git a/package.json b/package.json
index bc4276f1..c091e9f7 100644
--- a/package.json
+++ b/package.json
@@ -80,7 +80,7 @@
     "install": "(node install/libvips && node install/dll-copy && prebuild-install) || (node-gyp rebuild && node install/dll-copy)",
     "clean": "rm -rf node_modules/ build/ vendor/ .nyc_output/ coverage/ test/fixtures/output.*",
     "test": "semistandard && cpplint && npm run test-unit && npm run test-licensing",
-    "test-unit": "nyc --reporter=lcov --branches=99 mocha --slow=1000 --timeout=60000 ./test/unit/*.js",
+    "test-unit": "nyc --reporter=lcov --branches=99 mocha --parallel --slow=1000 --timeout=60000 ./test/unit/*.js",
     "test-licensing": "license-checker --production --summary --onlyAllow=\"Apache-2.0;BSD;ISC;MIT\"",
     "test-coverage": "./test/coverage/report.sh",
     "test-leak": "./test/leak/leak.sh",
diff --git a/test/unit/toFormat.js b/test/unit/toFormat.js
index bc253d03..acc680d5 100644
--- a/test/unit/toFormat.js
+++ b/test/unit/toFormat.js
@@ -5,22 +5,23 @@ const sharp = require('../../');
 const fixtures = require('../fixtures');
 
 describe('toFormat', () => {
-  it('accepts upper case characters as format parameter (string)', function (done) {
-    sharp(fixtures.inputJpg)
+  it('accepts upper case characters as format parameter (string)', async () => {
+    const data = await sharp(fixtures.inputJpg)
+      .resize(8, 8)
       .toFormat('PNG')
-      .toBuffer(function (err, data, info) {
-        if (err) throw err;
-        assert.strictEqual('png', info.format);
-        done();
-      });
+      .toBuffer();
+
+    const { format } = await sharp(data).metadata();
+    assert.strictEqual(format, 'png');
   });
-  it('accepts upper case characters as format parameter (object)', function (done) {
-    sharp(fixtures.inputJpg)
+
+  it('accepts upper case characters as format parameter (object)', async () => {
+    const data = await sharp(fixtures.inputJpg)
+      .resize(8, 8)
       .toFormat({ id: 'PNG' })
-      .toBuffer(function (err, data, info) {
-        if (err) throw err;
-        assert.strictEqual('png', info.format);
-        done();
-      });
+      .toBuffer();
+
+    const { format } = await sharp(data).metadata();
+    assert.strictEqual(format, 'png');
   });
 });