No crash for a bad filename if in memory only

lib/persistence.js

@@ -23,6 +23,14 @@ function Persistence (options) {
   this.db = options.db;
   this.inMemoryOnly = this.db.inMemoryOnly;
   this.filename = this.db.filename;
+  
+  if (!this.inMemoryOnly && this.filename) {
+	if (this.filename.charAt(this.filename.length - 1) === '~') {
+		throw "The datafile name can't end with a ~, which is reserved for automatic backup files";
+	} else {
+		this.tempFilename = this.filename + '~';
+	}
+  }
 
   // For NW apps, store data in the same directory where NW stores application data
   if (this.filename && options.nodeWebkitAppName) {
@@ -86,6 +94,8 @@ Persistence.prototype.persistCachedDatabase = function (cb) {
   var callback = cb || function () {}
     , toPersist = ''
     ;
+	
+  if (this.inMemoryOnly) { return callback(null); }	
 
   this.db.getAllData().forEach(function (doc) {
     toPersist += model.serialize(doc) + '\n';

test/persistence.test.js

@@ -252,10 +252,17 @@ describe('Persistence', function () {
   
   
   // This test is a bit complicated since it depends on the time actions take to execute
-  // It may not work as expected on all machines
-  // But it will not be seen as a failed test. The worst is that the timing is off and it would have worked on your machine regardless of the load failsafe
-  // It is timed for my dev machine
+  // It may not work as expected on all machines as it is timed for my machine
+  // That's why it is skipped, but all versions of nedb pass this test
   describe.only('Prevent dataloss when persisting data', function () {
+
+	it('Creating a datastore with in memory as true and a bad filename wont cause an error', function () {
+		new Datastore({ filename: 'workspace/bad.db~', inMemoryOnly: true });
+	})
+	
+	it('Creating a persistent datastore with a bad filename will cause an error', function () {
+		(function () { new Datastore({ filename: 'workspace/bad.db~' }); }).should.throw();
+	})  
   
     it('If system crashes during a loadDatabase, the former version is not lost', function (done) {
       var cp, N = 150000, toWrite = "", i;