Write a Python function named "convert$\_$temperature" that converts a temperature from Celsius to Fahrenheit and vice versa. The function should take two arguments: the temperature value and the scale to convert to $(\text{'}$ C $\text{'}$ for Celsius or $\text{'}$ F $\text{'}$ for Fahrenheit$).$ Implement the function such that convert$\_$temperature$(100,\text{'}$C$\text{'})$ returns $37\mathrm{.}78$ and convert$\_$temperature$(0,\text{'}F\text{'})$ returns $32\mathrm{.}0.$ Include test cases to verify your function works correctly.