diff --git a/tests/006-scalar.phpt b/tests/006-scalar.phpt
new file mode 100644
index 0000000..765eb2a
--- /dev/null
+++ b/tests/006-scalar.phpt
@@ -0,0 +1,22 @@
+--TEST--
+Test for `Internal\Scalar`.
+--SKIPIF--
+<?php
+require_once 'includes/loaded.php';
+is_php_arma_loaded();
+?>
+--FILE--
+<?php
+
+require_once 'includes/assert.php';
+
+$mat = Arma\IMat::fromString('1 2; 3 4');
+$mat(1, 0)->setTo(5);
+$mat->at(0, 1)->setTo(7);
+batch_assert('read/write access of `MapVal`',
+    [5, $mat->at(1, 0)->val()],
+    [7, $mat(0, 1)->val()]
+);
+
+?>
+--EXPECT--
diff --git a/tests/007-scalar-operators.phpt b/tests/007-scalar-operators.phpt
new file mode 100644
index 0000000..3a35e62
--- /dev/null
+++ b/tests/007-scalar-operators.phpt
@@ -0,0 +1,29 @@
+--TEST--
+Test for `Internal\Scalar`.
+--SKIPIF--
+<?php
+require_once 'includes/loaded.php';
+require_once 'includes/supports.php';
+if (is_php_arma_loaded()) {
+    supports_operator_overloading();
+}
+?>
+--FILE--
+<?php
+
+require_once 'includes/assert.php';
+
+$mat = Arma\IMat::fromString('1 2; 3 4');
+$mapval = $mat(1, 0);
+$mapval = 5;
+// Unfortunately, the Zend Engine prevents us from writing something like:
+// $mat(1, 0) = 5;
+// because function return values are not supposed to be used in write context.
+// Function `zend_ensure_writable_variable()` does that check in compile time.
+
+batch_assert('operator overloading of `MapVal`',
+    [5, +$mat->at(1, 0)],
+);
+
+?>
+--EXPECT--