Current testing practice in industry is often ineffective and slow to detect bugs, since most projects utilize manually generated test cases. Concolic testing alleviates this problem by automatically generating test cases that achieve high coverage. However, specialized execution platforms and resource constraints of embedded software hinder application of concolic testing to embedded software. To overcome these limitations, we have developed CONcrete and symBOLic (CONBOL) testing framework to unit test large size industrial embedded software automatically. To address the aforementioned limitations, CONBOL tests target units on a host PC platform by generating symbolic unit testing drivers/stubs automatically and applying heuristics to reduce false alarms caused by the imprecise drivers/stubs. We have applied CONBOL to four million lines long industrial embedded software and detected 24 new crash bugs. Furthermore, the development team of the target software adopted CONBOL to their development process to apply CONBOL to the revised target software regularly.