email_tests.cls

    static TestMethod void dealApprovalHandler_Tests_UnitTest(){
        Account acc = test_Helper.createAccount();
		Contact cont = test_Helper.createContact( acc );
		Opportunity deal = test_Helper.createOpportunity( acc, cont );
        // create a new email and envelope object

        Messaging.InboundEmail.Header h = new Messaging.InboundEmail.Header();
        h.Name = 'Test';
        h.Value = '      1   1 2000';
        Messaging.InboundEmail email = new Messaging.InboundEmail();
        email.headers = new List<Messaging.InboundEmail.Header>();
        email.headers.add(h);
        Messaging.InboundEnvelope env = new Messaging.InboundEnvelope();

        // setup the data for the email
        email.subject = 'Create Contact';
        email.fromAddress = 'someaddress@email.com';
        email.plainTextBody = 'email body\n2225256325\nTitle';
        String body = '<wbr>';
        body += '--DEALIDSTART--'+deal.id+'--DEALIDEND--';
        body += '--CONTENTIDSTART--'+''+'--CONTENTIDEND--';
        body += '--ATTACHMENTIDSTART--'+''+'--ATTACHMENTIDEND--';
        body += 'CoreVest American Finance Lender LLC. All Rights Reserved.';
        email.htmlBody = body;

        /* add an Binary attachment
        Messaging.InboundEmail.BinaryAttachment attachment = new Messaging.InboundEmail.BinaryAttachment();
        attachment.body = blob.valueOf(test);
        attachment.fileName = 'textfileone.txt';
        attachment.mimeTypeSubType = 'text/plain';
        email.binaryAttachments = new Messaging.inboundEmail.BinaryAttachment[] { attachment };
        // add an Text attachment

        Messaging.InboundEmail.TextAttachment attachmenttext = new Messaging.InboundEmail.TextAttachment();
        attachmenttext.body = 'my attachment text';
        attachmenttext.fileName = 'textfiletwo3.txt';
        attachmenttext.mimeTypeSubType = 'texttwo/plain';
        email.textAttachments =   new Messaging.inboundEmail.TextAttachment[] { attachmenttext };
        */
        // call the email service class and test it with the data in the testMethod
        dealApprovalHandler cls = new dealApprovalHandler();

        Test.startTest();
            deal = dealApprovalHandler.queryOpportunity(deal.Id);
            email.fromAddress = deal.Owner.email;
            email.toAddresses = new List<String>{'test@test.com'};

            cls.handleInboundEmail(email, env);

            dealApprovalHandler.postToChatter(deal,'test');

            Messaging.InboundEmail.TextAttachment t = new Messaging.InboundEmail.TextAttachment();
            t.fileName = 'Test';
            t.mimeTypeSubType = 'Test';
            t.body = 'Test';
            dealApprovalHandler.constructFileAttachment(t);

            Messaging.InboundEmail.BinaryAttachment b = new Messaging.InboundEmail.BinaryAttachment();
            b.fileName = 'Test';
            b.mimeTypeSubType = 'Test';
            b.body = blob.valueOf('Test');
            dealApprovalHandler.constructFileAttachment(b);

            dealApprovalHandler.queryContentVersions(new List<Id>{UserInfo.getUserId()});
            dealApprovalHandler.sendReply(deal.Id, UserInfo.getUserId());
            dealApprovalHandler.createAttachment(email,deal);
        Test.stopTest();