Fix #41: output order and subset (#126)

* init unparse tests for ordering and subseting by fields
* added one test for heading=false
* implements functionality of this issue

tests/methods/UnparseTest.php

@@ -0,0 +1,62 @@
+<?php
+namespace ParseCsv\tests\methods;
+
+use ParseCsv\Csv;
+use PHPUnit\Framework\TestCase;
+
+
+class UnparseTest extends Testcase {
+    /** @var Csv */
+    private $csv;
+
+    /**
+     * Setup our test environment objects; will be called before each test.
+     */
+    public function setUp() {
+        $this->csv = new Csv();
+        $this->csv->auto(__DIR__ . '/fixtures/auto-double-enclosure.csv');
+    }
+
+    public function testUnparseDefault() {
+        $expected = "column1,column2\rvalue1,value2\rvalue3,value4\r";
+        $this->unparseAndCompare($expected);
+    }
+
+    public function testUnparseDefaultWithoutHeading(){
+        $this->csv->heading = false;
+        $this->csv->auto(__DIR__ . '/fixtures/auto-double-enclosure.csv');
+        $expected = "column1,column2\rvalue1,value2\rvalue3,value4\r";
+        $this->unparseAndCompare($expected);
+
+    }
+
+    public function testUnparseRenameFields() {
+        $expected = "C1,C2\rvalue1,value2\rvalue3,value4\r";
+        $this->unparseAndCompare($expected, array("C1", "C2"));
+    }
+
+    public function testReorderFields() {
+        $expected = "column2,column1\rvalue2,value1\rvalue4,value3\r";
+        $this->unparseAndCompare($expected, array("column2", "column1"));
+    }
+
+    public function testSubsetFields() {
+        $expected = "column1\rvalue1\rvalue3\r";
+        $this->unparseAndCompare($expected, array("column1"));
+    }
+
+    public function testReorderAndRenameFields() {
+        $fields = array(
+            'column2' => 'C2',
+            'column1' => 'C1',
+        );
+        $expected = "C2,C1\rvalue2,value1\rvalue4,value3\r";
+        $this->unparseAndCompare($expected, $fields);
+    }
+
+    private function unparseAndCompare($expected, $fields = array()) {
+        $str = $this->csv->unparse($this->csv->data, $fields);
+        $this->assertEquals($expected, $str);
+    }
+
+}