! Good question. The full testimony is written down already when you go to court, in a document titled 'personal statement'. Your lawyers have to help in drafting this document, together with exhibits (evidence).
In court, it depends on the judge. Some will want you to recite the full testimony (very very rare). The majority of judges are not interested in hearing it again because they will have already read the whole court file, including the personal statement that your lawyers submit to the clerk of court ahead of the hearing. You have to be prepared to answer questions from the EOIR lawyers and also the judge. This is not a criminal case, so questions from the EOIR lawyers and judge are not dramatic
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Lastly, the judge has too many cases to adjudicate. They have no time to hear your story. Government lawyers (EOIR lawyers), are also handling too many cases, hard for them to know the facts of your case. I would bet my dollar that some of the government lawyers come to the hearing without reading your case file!
In my case, I was standing in the box. After the oath, judge said to recount my experiences...the basis of my claim...he stopped me within a minute! He asked the government lawyer...do you have questions for the defendant? He said no. Then quickly, he said I will deny the case based on 'credible fear of future persecution.' However, 'I will grant the case based on past contraventions of UN Human rights.' The court hearing was done in under ten minutes....more time spent on the judge signing the papers than the actual hearing.