diff --git a/QRCodeLibrary/BitArray.cpp b/QRCodeLibrary/BitArray.cpp
index 476a654..8a172c2 100644
--- a/QRCodeLibrary/BitArray.cpp
+++ b/QRCodeLibrary/BitArray.cpp
@@ -6,6 +6,8 @@
 
 bool BitArray::get(unsigned index) const
 {
+	if (index >= size) throw std::out_of_range("No such element in array");
+
     return (v[index / 8] >> (8 - 1 - index % 8)) & 1;
 }
 
@@ -21,6 +23,8 @@ BitArray::operator std::string() const
 
 void BitArray::set(unsigned index, bool val)
 {
+	if (index >= size) throw std::out_of_range("No such element in array");
+
 	if (val)
 		v[index / 8] |= 1 << (8 - 1 - index % 8);
 	else
@@ -29,8 +33,12 @@ void BitArray::set(unsigned index, bool val)
 
 unsigned BitArray::set(unsigned index, int32_t val, unsigned size)
 {
+	if (index >= this->size) throw std::out_of_range("No such element in array");
+
 	unsigned shift = index % 8, written = 0;
-	size = std::min(size, this->size - index);
+
+	if (size > this->size - index) throw std::out_of_range("Number of bits to write from this index is more than BitArray capability");
+
 	index /= 8;
 
 	while (written < size) {
@@ -48,3 +56,10 @@ unsigned BitArray::set(unsigned index, int32_t val, unsigned size)
 
 	return written;
 }
+
+void BitArray::resize(unsigned new_size)
+{
+	v.resize(ceil_div(new_size, 8));
+
+	size = new_size;
+}
diff --git a/QRCodeLibrary/BitArray.hpp b/QRCodeLibrary/BitArray.hpp
index 63d43e9..53d0dd6 100644
--- a/QRCodeLibrary/BitArray.hpp
+++ b/QRCodeLibrary/BitArray.hpp
@@ -22,5 +22,7 @@ public:
 	bool get(unsigned index) const;
 	void set(unsigned index, bool val);
 	unsigned set(unsigned index, int32_t val, unsigned size);
+
+	void resize(unsigned new_size);
 };
 
diff --git a/tests/BitArray_test.cpp b/tests/BitArray_test.cpp
index 98c5063..c1c9922 100644
--- a/tests/BitArray_test.cpp
+++ b/tests/BitArray_test.cpp
@@ -5,6 +5,12 @@
 
 #include "../QRCodeLibrary/BitArray.hpp"
 
+TEST(CeilDivTests, DividesCeilingResult) {
+	EXPECT_EQ(ceil_div(1, 3), 1);
+	EXPECT_EQ(ceil_div(4, 2), 2);
+	EXPECT_EQ(ceil_div(5, 2), 3);
+}
+
 class BitArrayTests: public ::testing::Test {
 public:
 	BitArrayTests() : ::testing::Test(), a1(15) {};