apply demeter law for transaction type calls

- adds contants for transaction type names
- demeter law = never speaks with strangers

tests/unit/ExampleTest.php

@@ -1,20 +0,0 @@
-<?php
-
-/**
- * Class ExampleTest
- */
-class ExampleTest extends \PHPUnit_Framework_TestCase
-{
-    protected function setUp()
-    {
-    }
-
-    protected function tearDown()
-    {
-    }
-
-    // tests
-    public function testMe()
-    {
-    }
-}

tests/unit/Models/TransactionTypeTest.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace FireflyIII\Models;
+
+use TestCase;
+
+class TransactionTypeTest extends TestCase
+{
+    public function testIsWithdrawal()
+    {
+        $transactionType = TransactionType::whereType(TransactionType::WITHDRAWAL)->first();
+        $this->assertTrue($transactionType->isWithdrawal());
+    }
+
+    public function testIsDeposit()
+    {
+        $transactionType = TransactionType::whereType(TransactionType::DEPOSIT)->first();
+        $this->assertTrue($transactionType->isDeposit());
+    }
+
+    public function testIsTransfer()
+    {
+        $transactionType = TransactionType::whereType(TransactionType::TRANSFER)->first();
+        $this->assertTrue($transactionType->isTransfer());
+    }
+
+    public function testIsOpeningBalance()
+    {
+        $transactionType = TransactionType::whereType(TransactionType::OPENING_BALANCE)->first();
+        $this->assertTrue($transactionType->isOpeningBalance());
+    }
+}