We report a nondestructive testing system based on near-field scanning microwave microscopy. The instrumentation is built up with a vector network analyzer, a fully automated tuning matching network and an evanescent microwave probe. The system can perform microwave images in the frequency band 0.1-20 GHz on scanning ranges of 25x25 cm(2). The spatial resolution is experimentally verified by investigating imaging of metal slots. A lumped element model is built to describe the probe-sample interaction.