Unfortunately Ken Johson reveals his complete ignorance by repeatedly calling the 'Testaments of the Twelve Patriarchs' the Dead Sea Scrolls. The TTP was not discovered among the collections at Qumran. Some evidence exists that some tiny fragments MAY represent an early Jewish Vorlage for some of the material in the TTP. However, the TTP as it is written is a product of many years of redaction and interpolation by Christians. In fact a number of scholars take the position that the work as a whole was an early Christian product that utilized Jewish material and traditions so as to make the ancient patriarchs prophesy about Jesus. A few Church Fathers seem aware of the work and may have been even quoting it at times.
After a fair amount of reading, I've concluded the work was originally Jewish and pre-Christian; however, it was obviously redacted in the centuries prior to its rediscovery in the 13th century by Bishop Richard Grosseteste. It was Richard's view (which Ken Johnson seems to be parroting) that the Jews hid the work to be able to deny Jesus. That view betrays an antisemitism that was of course common in the period and not scholarship.
The work, even in its interpolated form, has value for research of Christian origins. In my view the work as a whole is overtly pro-Judaism, the concepts and imagery consistent with a work from the 1rst century BCE.
As an example of the suggested interpolations:
19 1 Hear ye, therefore, me vision which I saw. 2 I saw twelve harts feeding. And nine of them were dispersed. Now the three were preserved, but on the following day they also were dispersed. 3 And I saw that the three harts became three lambs, and they cried to the Lord, and He brought them forth into a flourishing and well watered place, yea He brought them out of darkness into light. 4 And there they cried unto the Lord until there gathered together unto them the nine harts, and they became as twelve sheep, and after a little time they increased and became many 5 flocks. And after these things I saw and behold, twelve bulls were sucking one cow, which produced a sea of milk, and there drank thereof the twelve flocks and innumerable herds. 6 And the horns of the fourth bull went up unto heaven and became as a wall for the flocks, and in the midst of the two horns there grew 7 another horn. And I saw a bull calf which surrounded them twelve times, and it became a help to the bulls wholly. 8 And I saw in the midst of the horns a virgin [wearing a many-coloured garment, and from her] went forth a lamb; and on his right (was as it were a lion; and) all the beasts and all the reptiles rushed (against him), and the lamb over 9 came them and destroyed them. And the bulls rejoiced because of him, and the cow [and the 10 harts] exulted together with them. And these 11 things must come to pass in their season. Do ye therefore, my children, observe the commandments of the Lord, and honour Levi and Judah; for from them shall arise unto you [the Lamb of God, who taketh away the sin of the world] one who saveth [all the Gentiles and] Israel. 12 For His kingdom is an everlasting kingdom, which shall not pass away; but my kingdom among you shall come to an end as a watcher's hammock, which after the summer disappeareth.
The bold sections certainly would be suggestive of a Christian redactor modifying the text. I am reluctant to assume it is in entirety however. The language of the maiden/virgin wearing a colored outfit is difficult to explain if Christain. Also, the continuing reference to the bulls and harts seems difficult to explain as Christian , unless the redactor was convinced he understood the passage and imagery and assumed we the reader would also.
