add PIVector2D Index

tests/math/testpivector2d.cpp

@@ -1431,3 +1431,61 @@ TEST_F(Vector2DTest, iostream_operator_works) {
 	// No assertion, just ensure it runs
 }
 #endif
+
+// ==================== INDEX STRUCTURE ACCESS TESTS ====================
+TEST_F(Vector2DTest, operator_bracket_with_index_allows_read_access) {
+	PIVector2D<int>::Index idx = {5, 7};
+	int value                  = vec[idx];
+	int expected               = vec.element(5, 7);
+	EXPECT_EQ(value, expected);
+}
+
+TEST_F(Vector2DTest, operator_bracket_with_index_allows_write_access) {
+	PIVector2D<int>::Index idx = {10, 15};
+	vec[idx]                   = 999;
+	EXPECT_EQ(vec.element(10, 15), 999);
+}
+
+TEST_F(Vector2DTest, operator_bracket_with_const_index_works) {
+	const auto & constVec      = vec;
+	PIVector2D<int>::Index idx = {3, 12};
+	int value                  = constVec[idx];
+	int expected               = vec.element(3, 12);
+	EXPECT_EQ(value, expected);
+}
+
+TEST_F(Vector2DTest, element_function_with_index_works) {
+	PIVector2D<int>::Index idx = {8, 20};
+	int value                  = vec.element(idx);
+	int expected               = vec.element(8, 20);
+	EXPECT_EQ(value, expected);
+}
+
+TEST_F(Vector2DTest, element_function_with_index_modifies_value) {
+	PIVector2D<int>::Index idx = {12, 8};
+	vec.element(idx)           = 555;
+	EXPECT_EQ(vec.element(12, 8), 555);
+}
+
+TEST_F(Vector2DTest, element_function_with_const_index_works) {
+	const auto & constVec      = vec;
+	PIVector2D<int>::Index idx = {7, 5};
+	int value                  = constVec.element(idx);
+	int expected               = vec.element(7, 5);
+	EXPECT_EQ(value, expected);
+}
+
+TEST_F(Vector2DTest, at_function_with_index_works) {
+	PIVector2D<int>::Index idx = {4, 11};
+	int value                  = vec.at(idx);
+	int expected               = vec.at(4, 11);
+	EXPECT_EQ(value, expected);
+}
+
+TEST_F(Vector2DTest, index_structure_with_brace_initialization_works) {
+	vec[{0, 0}] = 100;
+	EXPECT_EQ(vec.element(0, 0), 100);
+
+	vec[{static_cast<ssize_t>(ROWS_COUNT_INIT - 1), static_cast<ssize_t>(COLS_COUNT_INIT - 1)}] = 200;
+	EXPECT_EQ(vec.element(ROWS_COUNT_INIT - 1, COLS_COUNT_INIT - 1), 200);
+}