Add test to catch issue with preserveCache not preserving correctly

test/proxyquire-cache.js

@@ -21,6 +21,17 @@ describe("Proxyquire", function() {
   });
 
   describe('preserveCache()', function() {
+
+    it('should return a cache of the module after first proxyquire call', function() {
+        var proxyquire = require('..').preserveCache();
+        var count1 = proxyquire('./samples/count', {});
+        var count2 = proxyquire('./samples/count', {});
+        var count3 = proxyquire('./samples/count', {});
+        assert.equal(count1(), 1);
+        assert.equal(count2(), 2);
+        assert.equal(count3(), 3);
+    });
+
     it('returns a reference to itself, so it can be chained', function() {
       var proxyquire = require('..');
       assert.equal(proxyquire.preserveCache(), proxyquire);
@@ -109,4 +120,4 @@ describe("Proxyquire", function() {
       })
     });
   });
-});
+});

test/samples/count.js

@@ -0,0 +1,4 @@
+var count = 0;
+module.exports = function() {
+    return ++count;
+};