Source: The Great Interpretation of Dreams (Ibn Sirin)
Testimony in a dream indicates paying off a debt or fulfilling a trust. False testimony indicates lying and misguidance.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
Testimony indicates exaltation and position. Whoever sees himself testifying to the truth, his status will rise.
Source: Signs in the Science of Expressions (Ibn Shaheen)
Testimony is interpreted as goodness. Whoever sees himself testifying will attain goodness.