#117 Add unit-tests covering lazy-loading

test/test-lazy-loading.ts

@@ -0,0 +1,35 @@
+import * as mm from '../src';
+import * as path from "path";
+import {assert} from "chai";
+import {Promise} from "es6-promise";
+
+describe("Lazy loading of format parser (ITokenParser", () => {
+
+  it("be able to override the loading method", () => {
+
+    const filePath = path.join(__dirname, "samples", "1971 - 003 - Sweet - Co-Co - CannaPower.mp2");
+
+    return mm.parseFile(filePath, {duration: true, native: true, loadParser: moduleName => {
+        assert.strictEqual(moduleName, 'mpeg');
+        const parserModule = require('../src/' + moduleName);
+        return Promise.resolve(new parserModule.default());
+      }
+    });
+  });
+
+  it("should throw an error if the parser cannot be loaded", () => {
+
+    const filePath = path.join(__dirname, "samples", "1971 - 003 - Sweet - Co-Co - CannaPower.mp2");
+
+    return mm.parseFile(filePath, {duration: true, native: true, loadParser: moduleName => {
+        assert.strictEqual(moduleName, 'mpeg');
+        return Promise.resolve(undefined);
+      }
+    }).then(() => {
+      assert.fail('Should throw an error');
+    }).catch(err => {
+      assert.strictEqual(err.message, 'options.loadParser failed to resolve module "mpeg".');
+    });
+  });
+
+});