what is bottom up integration testing code example

Example 1: what is bottom up integration testing

It is opposite of the Top-Down Approach. 
Testing takes place from bottom to up. 
Lowest level modules are tested first
and then high-level modules and finally
integrating the high-level modules to a
low level to ensure the system is 
working as intended.  Drivers are used
as a temporary module for integration testing.

Example 2: what is bottom up integration testing

It is opposite of the Top-Down Approach. 
Testing takes place from bottom to up. 
Lowest level modules are tested first
and then high-level modules and finally
integrating the high-level modules to a
low level to ensure the system is 
working as intended.  Drivers are used
as a temporary module for integration testing.