Add test for `save()` and `load()` of `Mat`.

tests/004-mat-save-load.phpt

@@ -0,0 +1,39 @@
+--TEST--
+Test save/load for `Arma\Mat`.
+--SKIPIF--
+<?php
+require_once 'includes/loaded.php';
+is_php_arma_loaded();
+?>
+--FILE--
+<?php
+
+require_once 'includes/assert.php';
+
+$file_name = 'test_mat_data';
+
+$mat = Arma\CxDMat::fromString('(1 2) (3 4); (5 6) (7 8)');
+batch_assert('saving/loading of `Arma\\Mat`',
+    [true, $mat->save($file_name, Arma\FileType::ARMA_BINARY)]
+);
+
+$mat1 = Arma\CxDMat::init();
+$handle = fopen($file_name, 'r');
+batch_assert('saving/loading of `Arma\\Mat`',
+    [true, $mat1->load($handle, Arma\FileType::ARMA_BINARY)]
+);
+
+$eq_mat = $mat->equals($mat1);
+batch_assert('saving/loading of `Arma\\Mat`',
+    [1, $eq_mat->min()],
+    [1, $eq_mat->max()]
+);
+
+?>
+--CLEAN--
+<?php
+if (file_exists($file_name)) {
+    unlink($file_name);
+}
+?>
+--EXPECT--