refactor power to pow and name test case

src/calc.cpp

@@ -8,7 +8,7 @@ int plus(    int a, int b) { return a + b; }
 int minus(   int a, int b) { return a - b; }
 int multiply(int a, int b) { return a * b; }
 int divide(  int a, int b) { return a / b; }
-int power(   int a, int b) { return std::pow(a, b); }
+int pow(   int a, int b) { return std::pow(a, b); }
 
 int pop_stack(auto &stack) {
   const auto ret{stack.top()};
@@ -31,7 +31,7 @@ int evaluate(const std::string &s) {
     case '-': change_stack_state(minus,    stack); break;
     case '*': change_stack_state(multiply, stack); break;
     case '/': change_stack_state(divide,   stack); break;
-    case '^': change_stack_state(power,    stack); break;
+    case '^': change_stack_state(pow,    stack); break;
     case '0'...'9': stack.push(c - '0'); break;
     }
   }

test/test.cpp

@@ -7,7 +7,7 @@ TEST_CASE( "some example calculations", "[calc]") {
   REQUIRE( evaluate("12+2-3*") == 3 );
 }
 
-TEST_CASE( "", "[calc]") {
+TEST_CASE( "pow function works", "[calc]") {
   REQUIRE( evaluate("22^") == 4 );
   REQUIRE( evaluate("43^") == 64 );
   REQUIRE_FALSE( evaluate("11^") == 2);