test($test): Rename zip to unzip for clarity. Add descriptive error message to

Added unit tests for unzip and added a user-friendly error message for unzip being unable to perform
its duties of extracting a project.json from the given input (zip).

lib/unpack.js

@@ -1,4 +1,4 @@
-var zip = require('./zip');
+var unzip = require('./unzip');
 
 /**
  * If input a buffer, transforms buffer into a UTF-8 string.
@@ -45,5 +45,5 @@ module.exports = function (input, callback) {
     // Return error if legacy encoding detected
     if (isLegacy) return callback('Parser only supports Scratch 2.X');
 
-    zip(input, callback);
+    unzip(input, callback);
 };

lib/unzip.js

@@ -0,0 +1,22 @@
+var JSZip = require('jszip');
+
+/**
+ * Unpacks a zip
+ *
+ * @param {String} Input
+ *
+ * @return {Object}
+ */
+module.exports = function (input, callback) {
+    return JSZip.loadAsync(input)
+        .then(function (zip) {
+            return zip.file('project.json').async('string')
+                .then(function (project) {
+                    return callback(null, [project, zip]);
+                });
+        })
+        .catch(function(err) {
+            var msg = 'Failed to unzip and extract project.json, with error: ';
+            return callback(msg + JSON.stringify(err));
+        });
+};

lib/zip.js

@@ -1,20 +0,0 @@
-var JSZip = require('jszip');
-
-/**
- * Unpacks a zip
- *
- * @param {String} Input
- *
- * @return {Object}
- */
-module.exports = function (input, callback) {
-    JSZip.loadAsync(input).then(function (zip) {
-        zip.file('project.json').async('string')
-            .then(function (project) {
-                callback(null, [project, zip]);
-            })
-            .catch(function (err) {
-                callback(err);
-            });
-    });
-};

test/unit/unzip.js

@@ -0,0 +1,114 @@
+var fs = require('fs');
+var path = require('path');
+var test = require('tap').test;
+var JSZip = require('jszip');
+var unzip = require('../../lib/unzip');
+
+var fixtures = {
+    sb: path.resolve(__dirname, '../fixtures/data/_example.sb'),
+    sb2: path.resolve(__dirname, '../fixtures/data/_example.sb2'),
+    zipFakeProjectJSON:
+        path.resolve(__dirname, '../fixtures/data/_zipFakeProjectJson.zip'),
+    zipNoProjectJSON:
+        path.resolve(__dirname, '../fixtures/data/_zipNoProjectJson.zip')
+};
+
+for (var i in fixtures) {
+    fixtures[i] = fs.readFileSync(fixtures[i]);
+}
+
+test('spec', function (t) {
+    t.type(unzip, 'function');
+    t.end();
+});
+
+test('sb', function (t) {
+    var buffer = new Buffer(fixtures.sb);
+    unzip(buffer, function (err, res) {
+        t.type(err, 'string');
+        var errorMessage = 'Failed to unzip and extract project.json';
+        t.equal(err.startsWith(errorMessage), true);
+        t.type(res, 'undefined');
+        t.end();
+    });
+});
+
+test('sb2', function (t) {
+    var buffer = new Buffer(fixtures.sb2);
+    unzip(buffer, function (err, res) {
+        t.equal(err, null);
+        t.equal(Array.isArray(res), true);
+        t.type(res[0], 'string');
+        t.doesNotThrow(function () {
+            JSON.parse(res[0]);
+        });
+        t.equal(res[1] instanceof JSZip, true);
+        t.end();
+    });
+});
+
+test('zip without project json', function (t) {
+    var buffer = new Buffer(fixtures.zipNoProjectJSON);
+    unzip(buffer, function (err, res) {
+        t.type(err, 'string');
+        var errorMessage = 'Failed to unzip and extract project.json';
+        t.equal(err.startsWith(errorMessage), true);
+        t.type(res, 'undefined');
+        t.end();
+    });
+});
+
+test('zip with fake project json', function (t) {
+    var buffer = new Buffer(fixtures.zipFakeProjectJSON);
+    unzip(buffer, function(err, res) {
+        t.equal(err, null);
+        t.equal(Array.isArray(res), true);
+        t.type(res[0], 'string');
+        t.equal(res[0], 'this is not json\n');
+        t.throws(function() {
+            JSON.parse(res[0]);
+        });
+        t.equal(res[1] instanceof JSZip, true);
+        t.end();
+    });
+});
+
+test('random string instead of zip', function (t) {
+    unzip('this is not a zip', function (err, res) {
+        t.type(err, 'string');
+        var errorMessage = 'Failed to unzip and extract project.json';
+        t.equal(err.startsWith(errorMessage), true);
+        t.type(res, 'undefined');
+        t.end();
+    });
+});
+
+test('undefined', function (t) {
+    unzip(undefined, function (err, res) {
+        t.type(err, 'string');
+        var errorMessage = 'Failed to unzip and extract project.json';
+        t.equal(err.startsWith(errorMessage), true);
+        t.equal(res, undefined);
+        t.end();
+    });
+});
+
+test('null', function (t) {
+    unzip(null, function (err, obj) {
+        t.type(err, 'string');
+        var errorMessage = 'Failed to unzip and extract project.json';
+        t.equal(err.startsWith(errorMessage), true);
+        t.equal(obj, undefined);
+        t.end();
+    });
+});
+
+test('object', function (t) {
+    unzip({}, function (err, obj) {
+        t.type(err, 'string');
+        var errorMessage = 'Failed to unzip and extract project.json';
+        t.equal(err.startsWith(errorMessage), true);
+        t.equal(obj, undefined);
+        t.end();
+    });
+});