## Crafting Reliable C++ Calculators with Unit Testing

Explore our comprehensive guide on building a robust C++ calculator, where we provide step-by-step instructions to enhance your coding skills. Whether you're a beginner or an experienced programmer, this resource will assist you in mastering C++ and help with your C++ assignment by improving your code validation techniques for creating reliable calculators. Join us on this coding journey to boost your confidence and deliver error-free C++ assignments with ease.

## Block 1: Header Inclusions

```
```cpp
#include < gtest/ gtest.h >
#include < iostream >
#include < vector >
#include < string >
#include < algorithm >
#include "calc.hpp"
```
```

This block includes necessary C++ standard library headers (`iostream`, `vector`, `string`, `algorithm`) and headers from the Google Test framework (`gtest/gtest.h`). It also includes a custom header file `"calc.hpp"` that likely contains the `Calc` class definition.

## Block 2: Test Cases for Addition

```
```cpp
TEST(Calc, addTwoNumbers)
{
std::string input{"3 +5"};
EXPECT_EQ(Calc::eval(input), 8);
}
TEST(Calc, addTwoBiggerNumbers)
{
std::string input{"123+ 576"};
EXPECT_EQ(Calc::eval(input), 699);
}
```
```

These test cases evaluate the addition operation. They provide input strings with addition expressions and use `EXPECT_EQ` to check if the result of `Calc::eval(input)` matches the expected results.

## Block 3: Test Cases for Subtraction

```
```cpp
TEST(Calc, subtractTwoNumbers)
{
std::string input{"5 - 8"};
EXPECT_EQ(Calc::eval(input), -3);
}
TEST(Calc, subtractTwoBiggerNumbers)
{
std::string input{"5000 - 8"};
EXPECT_EQ(Calc::eval(input), 4992);
}
```
```

These test cases evaluate the subtraction operation. They use input strings with subtraction expressions and `EXPECT_EQ` to compare the results to the expected values.

## Block 4: Test Cases for Division

```
```cpp
TEST(Calc, divideTwoNumbers)
{
std::string input{"8/3"};
EXPECT_EQ(Calc::eval(input), 2);
}
TEST(Calc, divideTwoBiggerNumbers)
{
std::string input{"1000/103"};
EXPECT_EQ(Calc::eval(input), 9);
}
```
```

These test cases focus on the division operation. They provide input strings with division expressions and use `EXPECT_EQ` to verify the calculated results against the expected outcomes.

## Block 5: Test Cases for Multiplication

```
```cpp
TEST(Calc, multiplyTwoNumbers)
{
std::string input{"12 * 13"};
EXPECT_EQ(Calc::eval(input), 156);
}
TEST(Calc, multiplyTwoBiggerNumbers)
{
std::string input{"120 * 136"};
EXPECT_EQ(Calc::eval(input), 16320);
}
```
```

These test cases assess the multiplication operation. Input strings with multiplication expressions are given, and `EXPECT_EQ` is used to validate the results.

## Block 6: Test Cases for Error Conditions

```
```cpp
TEST(Calc, divideByZero)
{
std::string input{"(3+5) / ((8-3) * 0)"};
EXPECT_THROW(Calc::eval(input), std::runtime_error);
}
TEST(Calc, divideByZeroAgain)
{
std::string input{"(3+5) / (8 / 3 -2 )"};
EXPECT_THROW(Calc::eval(input), std::runtime_error);
}
```
```

These test cases are designed to verify error handling. They contain input expressions that would result in division by zero and use `EXPECT_THROW` to check if a `std::runtime_error` is thrown.

## Block 7: Test Cases for Complex Expressions

```
```cpp
TEST(Calc, compoundExpression)
{
std::string input{"3 * 4 + (2-1)"};
EXPECT_EQ(Calc::eval(input), 13);
}
// More complex expression test cases follow...
```
```

These test cases evaluate more complex mathematical expressions, combining multiple arithmetic operations. The `EXPECT_EQ` statement is used to compare the computed results with expected values.

## Block 8: Test Cases for Associativity

```
```cpp
TEST(Calc, leftAssociative)
{
std::string input{"10/2/2"};
EXPECT_EQ(Calc::eval(input), 2);
}
TEST(Calc, sameExampleWithParens)
{
std::string input{"10/(2/2)"};
EXPECT_EQ(Calc::eval(input), 10);
}
```
```

These test cases examine the associativity of the division operation. They compare the result of left-associative and parentheses-enclosed division expressions using `EXPECT_EQ`.

## Block 9: Test Cases for a Complex Formula

```
```cpp
TEST(Calc, biggerFormula)
{
std::string input{"(9 - 4)* (3 - 2 + 7 - 2 *3)"};
EXPECT_EQ(Calc::eval(input), 10);
}
```
```

This test case assesses a more extensive and nested mathematical expression. The expected result is compared to the computed result using `EXPECT_EQ`.

## Block 10: Test Case for Summation

```
```cpp
TEST(Calc, gauss)
{
std::string input{};
for (int i = 1; i < 100; ++i)
{
input.append(std::to_string(i));
input.push_back('+');
}
input.append("100");
EXPECT_EQ(Calc::eval(input), 5050);
}
```
```

This test case calculates the sum of the first 100 natural numbers using a loop to construct the input string. The result is then compared to the expected value using `EXPECT_EQ`.

## Block 11: `main` Function

```
```cpp
int main(int argc, char *argv[])
{
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}
```
```

The `main` function initializes the Google Test framework and runs all the defined test cases using `RUN_ALL_TESTS()`.
The `main` function initializes the Google Test framework and runs all the defined test cases using `RUN_ALL_TESTS()`.

## Conclusion

In conclusion, the code consists of a series of test cases that evaluate the functionality of the Calc class for different mathematical expressions and edge cases, checking both valid and error scenarios. These tests help ensure the correctness of the calculator implementation. By applying the principles and techniques presented in this guide, you'll not only gain a solid grasp of unit testing in C++ but also develop a more profound appreciation for the reliability and robustness of your code. Armed with the knowledge acquired here, you can confidently tackle complex programming challenges and build software that stands up to the highest standards of quality and precision. Unit testing is a fundamental skill for any programmer, and you are now well-equipped to make it an integral part of your development process. Happy coding and testing!