Test code refactor #63

Use mocha for feature-specific unit tests

Add test coverage report via istanbul

test/unit/util.js

@@ -0,0 +1,38 @@
+'use strict';
+
+var assert = require('assert');
+var sharp = require('../../index');
+
+var defaultConcurrency = sharp.concurrency();
+
+describe('Utilities', function() {
+
+  describe('Cache', function() {
+    it('Can be disabled', function() {
+      sharp.cache(0);
+    });
+    it('Can be set to a maximum of 50MB and 500 items', function() {
+      sharp.cache(50, 500);
+    });
+  });
+
+  describe('Concurrency', function() {
+    it('Can be set to use 16 threads', function() {
+      sharp.concurrency(16);
+      assert.strictEqual(16, sharp.concurrency());
+    });
+    it('Can be reset to default', function() {
+      sharp.concurrency(0);
+      assert.strictEqual(defaultConcurrency, sharp.concurrency());
+    });
+  });
+
+  describe('Counters', function() {
+    it('Have zero value at rest', function() {
+      var counters = sharp.counters();
+      assert.strictEqual(0, counters.queue);
+      assert.strictEqual(0, counters.process);
+    });
+  });
+
+});