Abstract: The present invention relates to a built-in self test of a flash memory device in a data processing device, particularly a mobile terminal, comprising a flash-memory having a plurality of data blocks, a data block memory for temporarily storing a data block of said data blocks, a CPU and a test memory comprising a stored test program executable by the CPU, wherein the method comprises: a) fetching data from a first data block of said plurality of data blocks of the flash-memory; b) storing the fetched data temporarily in the data block memory; c) fetching a test pattern from the test memory, d) writing said test pattern into the first data block; e) reading back the test pattern that was written into the first data block; f) performing a data block test to see whether the first data block is corrupt or not by comparing the test pattern that was written into the first data block in step d) with the test pattern that was read back in step e) g) reporting the results of the data block test performed in step f);