Test code refactor #63

Use mocha for feature-specific unit tests

Add test coverage report via istanbul

test/unit/alpha.js

@@ -0,0 +1,49 @@
+'use strict';
+
+var assert = require('assert');
+
+var sharp = require('../../index');
+var fixtures = require('../fixtures');
+
+describe('Alpha transparency', function() {
+
+  it('Flatten to black', function(done) {
+    sharp(fixtures.inputPngWithTransparency)
+      .flatten()
+      .resize(400, 300)
+      .toFile(fixtures.path('output.flatten-black.jpg'), done);
+  });
+
+  it('Flatten to RGB orange', function(done) {
+    sharp(fixtures.inputPngWithTransparency)
+      .flatten()
+      .background({r: 255, g: 102, b: 0})
+      .resize(400, 300)
+      .toFile(fixtures.path('output.flatten-rgb-orange.jpg'), done);
+  });
+
+  it('Flatten to CSS/hex orange', function(done) {
+    sharp(fixtures.inputPngWithTransparency)
+      .flatten()
+      .background('#ff6600')
+      .resize(400, 300)
+      .toFile(fixtures.path('output.flatten-hex-orange.jpg'), done);
+  });
+
+  it('Ignored for JPEG', function(done) {
+    sharp(fixtures.inputJpg)
+      .background('#ff0000')
+      .flatten()
+      .resize(500, 400)
+      .toBuffer(function(err, data) {
+        if (err) throw err;
+        sharp(data).metadata(function(err, metadata) {
+          if (err) throw err;
+          assert.strictEqual('jpeg', metadata.format);
+          assert.strictEqual(3, metadata.channels);
+          done();
+        });
+      });
+  });
+
+});