Test: UnitTest for overloading of operator "()" (#1917)

Author: SeptemberMy

source/module_base/test/complexarray_test.cpp

@@ -71,6 +71,7 @@
 *   - function point_mult()
 *   - function complexArrayxAlloc
 *   - overloading of the function scaled_sum(). Does cd3 = c1*cd1 + c2*cd2. c1 and c2 are complex numbers.
+*   - overloading of operator "()". The operator is effectively overload by "const". 
 */
 
 //compare two complex by using EXPECT_DOUBLE_EQ()
@@ -501,3 +502,10 @@ TEST_F(ComplexArray_test,scaled_sum_2)
         EXPECT_COMPLEX_EQUAL(c2.ptr[i],com3*com1 + com3*com2);
     } 
 }
+
+TEST_F(ComplexArray_test,operator_parentheses_const)
+{
+    a2=com1;
+    const ModuleBase::ComplexArray ca2=a2;
+    EXPECT_COMPLEX_EQUAL(ca2(0,0,0,0), com1);
+}