Is the testimony of a slave valid in matters outside of Hadd punishments and Qisas (retaliation)?

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The established doctrine holds that the testimony of a slave is accepted in matters other than Hadd punishments and Qisas. This view is narrated from Ali and Anas, with Anas stating he knew of no one who rejected the testimony of a slave. This position is also held by Urwah, Shurayh, Iyas, Ibn Sirin, Al-Batti, Abu Thawr, Dawud, and Ibn al-Mundhir. The proof is the generality of the verses concerning testimony, as the slave is included among men and is considered just, meaning his reports, legal opinions, and religious narrations are accepted. Furthermore, a slave is just and without suspicion, thus his testimony should be accepted like that of a free man. A narration concerning a slave woman who claimed breastfeeding required the Prophet, peace be upon him, to acknowledge her statement, saying, 'How could you know otherwise, since she has said what she said?'